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100 years of military history

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Public Domain

100 years of military history

The world's mightiest military came from humble beginnings as colonial militias representative of the era’s free, white society. Men between the ages of 16 and 60 were recruited to colonial militia service from all walks of life, including shopkeepers, tutors, small farmers, and smiths. Left out of that recruitment were college enrollees, slaves, most free blacks, and clergy—and, in Virginia, Catholics. Men who were recruited were asked to make inarguably heavy sacrifices during their service, which included operations against Native Americans and supplementing Red Coats in border skirmishes with neighboring European colonies. The colonial militia’s first overseas foray came in 1741 and ended in abject disaster when 4,000 American reinforcements joined an attempted British invasion of Cartagena, Colombia, then a Spanish possession. The invasion failed miserably and only around 600 American volunteers returned home alive from the expedition.

In the lead up to the Revolutionary War, the American militia was prepared to step up in case of emergency for the paid, trained soldiers in the Continental Army (established by the Continental Congress in 1775), although the militia ultimately provided far more soldiers for that effort than the fledgling army. The British Regulars, or Red Coats, assumed this growing military was made up of laborers, criminals, and other struggling members of society, and ill-equipped to handle the brutality of war. That misguided perspective—largely brought about because Britain itself enlisted soldiers from its own, lowest classes—along with a big boost from the French ultimately cost Britain the colonies during the Revolutionary War.

The U.S. Armed Forces over the last century have played major roles in two world wars, a wide variety of civil conflicts, and dozens of ongoing military campaigns. These efforts have made significant impacts on how our government makes decisions that may affect domestic and foreign affairs. The military itself has undergone a few structural changes in that time as well, including adding new divisions and permitting women and LGBTQ people to serve in all military branches.

Stacker looked at information from the Defense Manpower Data Center, the U.S. Census historical population tables, and the St. Louis Federal Reserve to see how the military has changed over the years. By comparing data sets (last updated 2019) we were able to determine the percentage of Americans enlisted in the military and the number of Americans in each military branch every year from 1917 to 2019.

You may also like: 50 ways the military has changed in the last 50 years

[Pictured: Selected senior American commanders of the European theater of World War II]

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Public Domain

1917: U.S. enters WWI

- Army strength: 421,467 people
- Navy strength: 194,617 people
- Marine Core strength: 27,749 people
- Air Force strength: Not yet formed
- Total strength: 643,833 people
- Percent of population enlisted: 0.62%

Congress granted President Woodrow Wilson's request for a declaration of war against Germany on April 6, 1917, officially entering the United States into World War I. The Army expanded dramatically in the next 18 months, from 200,000 men in December 1916 to 3,685,000 troops in 1918—2 million of whom were stationed in France to serve in Gen. John Pershing's American Expeditionary Force.

[Pictured: President Woodrow Wilson delivering his war message in the Senate Chamber, July 2, 1917]

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U.S. National Archives

1918: Meuse-Argonne Offensive

- Army strength: 2,395,742 people
- Navy strength: 448,606 people
- Marine Core strength: 52,819 people
- Air Force strength: Not yet formed
- Total strength: 2,897,167 people
- Percent of population enlisted: 2.81%

Thousands of American troops joined forces in September 1918 with the allied intervention force at Archangel in response to the Bolshevik revolution in Russia. American soldiers engaged in several major battles that year as part of World War I, including the Meuse-Argonne Offensive from Sept. 26 through Nov. 11, which involved more than 1 million American soldiers (26,000 of whom died in battle and 120,000 casualties overall). The offensive was the largest of the American Expeditionary Forces in World War I and is largely credited with ushering in the end of the war on Nov. 11, 1918.

[Pictured: U.S. Marines during the Meuse-Argonne Campaign]

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Public Domain

1919: Treaty of Versailles

- Army strength: 851,624 people
- Navy strength: 272,144 people
- Marine Core strength: 48,834 people
- Air Force strength: Not yet formed
- Total strength: 1,172,602 people
- Percent of population enlisted: 1.12%

Following the conclusion of WWI, the Treaty of Versailles was signed June 28, 1919, in the Palace of Versailles, France. The peace document included signatures from allied powers and Germany and went into effect the following year with redrawn German boundaries and an outline of required reparations from the country. After signing the treaty on behalf of the United States and presenting his Fourteen Points that included the formation of the League of Nations, U.S. President Woodrow Wilson returned home only to find an obstinate Senate had voted against the treaty—twice.

[Pictured: The signing of the Treaty of Versailles on 28 June 1919]

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Public Domain

1920: National Defense Act amended

- Army strength: 204,292 people
- Navy strength: 121,845 people
- Marine Core strength: 17,165 people
- Air Force strength: Not yet formed
- Total strength: 343,302 people
- Percent of population enlisted: 0.32%

Congress in 1920 passed an amendment to the National Defense Act, which rejected the concept of an expandable “Regular Army” and called for the U.S. Army to have three main divisions: the standing Regular Army, National Guard, and Organized Reserves.

[Pictured: Officers of the 8th Surveillance Squadron, McAllen Field, Texas, 1920]

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United States Marine Corps // Wikimedia Commons

1921: The Unknown Soldier

- Army strength: 230,725 people
- Navy strength: 132,827 people
- Marine Core strength: 22,990 people
- Air Force strength: Not yet formed
- Total strength: 386,542 people
- Percent of population enlisted: 0.36%

Congress approved the burial of an unidentified body from World War I on March 4, 1921, at Arlington National Cemetery. The "Unknown Soldier" commemorates the 116,516 American soldiers killed in World War I, many of whose bodies were never identified.

[Pictured: Unknown Soldier is laid to rest in Arlington National Cemetery on 11 November, 1921 ]

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Public Domain

1922: Washington Naval Treaty

- Army strength: 148,763 people
- Navy strength: 100,211 people
- Marine Core strength: 21,233 people
- Air Force strength: Not yet formed
- Total strength: 270,207 people
- Percent of population enlisted: 0.25%

The Washington Naval Treaty was signed by the United States, United Kingdom, Japan, France, and Italy on Feb. 6, 1922. The document, also known as the Five-Power Treaty, was drafted to prevent an arms race following World War I.

[Pictured: American Legion Weekly highlighting the plight of unemployed American veterans in 1922]

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Public Domain

1923: Warlordism

- Army strength: 133,243 people
- Navy strength: 94,094 people
- Marine Core strength: 19,694 people
- Air Force strength: Not yet formed
- Total strength: 247,031 people
- Percent of population enlisted: 0.22%

American soldiers spent part of 1923 in China, helping to control unrest that ensued amidst warlordism—the era from 1923 to 1928 marked by the dilemma of Beiyang Army military factions vying for control of China. The period of time represents a division of control spread out across the country.

[Pictured: Two Airco DH-4B biplanes perform the first ever mid-air refueling on June 27, 1923]

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Richard // Wikimedia Commons

1924: First U.S. occupation of Dominican Republic ends

- Army strength: 142,673 people
- Navy strength: 98,184 people
- Marine Core strength: 20,332 people
- Air Force strength: Not yet formed
- Total strength: 261,189 people
- Percent of population enlisted: 0.23%

The U.S. Navy invaded the Dominican Republic in 1916, taking over the army, police, and several vital locations as Desiderio Arias, the Dominican Republic’s secretary of war, was forced out of Santo Domingo. The occupation lasted through 1924, when waning public support following World War I and significant opposition internationally and among Dominicans inspired the U.S. to turn policing authority over to the Guardia Nacional. Back home, the Immigration Act of 1924 allowed immigration visas for 2% of the number of people from each nationality in the U.S. according to the 1890 census. The act neglected to include visas for any immigrants from Asia, making it illegal for them to cross the U.S. shoreline and enter in spite of continued unrest overseas.

[Pictured: First Regiment Band, US Marine Corps, Santo Domingo, Dominican Republic]

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Public Domain

1925: Riots in Shanghai

- Army strength: 137,048 people
- Navy strength: 95,230 people
- Marine Core strength: 19,478 people
- Air Force strength: Not yet formed
- Total strength: 251,756 people
- Percent of population enlisted: 0.22%

Continued unrest from Chinese factions competing for political power in Shanghai erupted into riots. American troops were brought in to protect the public—and the terms of the Shanghai International Settlement during one of the most pivotal moments in Chinese history.

[Pictured: Arrival of Dutch marines from the SS Sumatra in Shanghai]

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The U.S. National Archives // Flickr

1926: U.S. squashes Nicaraguan coup d’état

- Army strength: 134,938 people
- Navy strength: 93,304 people
- Marine Core strength: 19,154 people
- Air Force strength: Not yet formed
- Total strength: 247,396 people
- Percent of population enlisted: 0.21%

The 1912 to 1933 U.S. occupation of Nicaragua was part of the “Banana Wars,” a period of various military interventions, massacres, and actions by the U.S. throughout the Caribbean and Central America following the Spanish-American War’s 1898 conclusion and the 1934 establishment of the Good Neighbor Policy. U.S. military presence in Nicaragua chiefly functioned to protect American business interests (soldiers kept unrest at a minimum on plantations the U.S. had a stake in and break apart any uprisings) and thwart any other would-be occupiers from constructing the Nicaraguan Canal. In 1925, the election of conservative President Carlos Solorzano helped form a coalition government. Thirteen years into their occupation, the U.S. Marines left Nicara. But by October of that year, Nicaraguan Gen. Emiliano Chamorro Vargas staged a successful coup d’état against Solorzano. Chamorro became president, but the U.S. did not recognize his rule; after a liberal revolt, the U.S. military in January 1926 sent gun-boats and troops back into the country and forced Vargas’ resignation.

[Pictured: Harry Truman talking to an unidentified soldier at Fort Riley, Kansas, July, 1926]

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Public Domain

1927: ‘China Marines’ in Shanghai

- Army strength: 134,829 people
- Navy strength: 94,916 people
- Marine Core strength: 19,198 people
- Air Force strength: Not yet formed
- Total strength: 248,943 people
- Percent of population enlisted: 0.21%

The 4th Regiment of the U.S. Marine Corps was sent to China in January 1927 to protect American citizens—and U.S. business interests—there in the midst of Shanghai’s ongoing civil unrest. Called the “ China Marines,” these members of the military would remain in Shanghai through 1941. On April 12, 1927, 5,000 people from Generalissimo Chiang Kai-shek’s military forces and the Nationalist Party Kuomintang staged a violent squashing of the Communist Party of China known as the Shanghai Massacre, or April 12 Purge. Hundreds of Communists were captured, tortured or executed, and the action touched off years of anti-communist violence coined the “White Terror.”

[Pictured: U.S. President Calvin Coolidge in 1927]

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Public Domain

1928: Lt. Schilt receives Medal of Honor

- Army strength: 136,084 people
- Navy strength: 95,803 people
- Marine Core strength: 19,020 people
- Air Force strength: Not yet formed
- Total strength: 250,907 people
- Percent of population enlisted: 0.21%

First Lt. Christian F. Schilt between Jan 6 and 8, 1928, took it upon himself to make 10 trips in his Vought O2U Corsair aircraft into Quilali, Nicaragua, in order to evacuate 18 U.S. Marines who had been injured in the conflict there. These takeoffs were accomplished amidst burning villages and extensive enemy fire, according to the U.S. Marine Corps, however Schilt completed his mission, saved three lives in the process, delivered necessary provisions, and in June of 1928 was awarded the Medal of Honor.

[Pictured: U.S. President Calvin Coolidge in 1928]

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Public Domain

1929: Cayes Massacre

- Army strength: 139,118 people
- Navy strength: 97,117 people
- Marine Core strength: 18,796 people
- Air Force strength: Not yet formed
- Total strength: 255,031 people
- Percent of population enlisted: 0.21%

The U.S. occupation of Haiti began in 1915 as a means of keeping the country from German occupation that could disrupt passage through the Panama Canal. By 1929, there was deep resentment against Americans for their roles in censoring the press, collecting customs duties, being the distributor of essentials like food and medicine, and for forcing a new constitution upon the Haitians which. Uprisings were commonplace, including a 1 918 guerrilla war that rose up against U.S.-imposed forced labor to build roads through the country. On Dec. 6, 1929, U.S. Marine battalions in Les Cayes opened fire on 1,500 protestors who were part of a national strike and area rebellion. Twelve Haitians were killed and 23 wounded in the massacre. Worldwide backlash from this violence helped to eventually inspire the end of the U.S. occupation there.

[Pictured: Wendell Neville and Smedley Butler Review Marines, 31 October 1929]

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Hulton Archive // Getty Images

1930: London Naval Treaty

- Army strength: 139,378 people
- Navy strength: 96,890 people
- Marine Core strength: 19,380 people
- Air Force strength: Not yet formed
- Total strength: 255,648 people
- Percent of population enlisted: 0.21%

France, Italy, the United Kingdom, Japan, and the U.S. signed the Treaty for the Limitation and Reduction of Naval Armament (commonly referred to as the London Naval Treaty) on April 22, 1930, to regulate submarine warfare and limit the building of naval ships. The terms of the treaty were put in place to avert a naval arms race following WWI and to build upon the Five Powers Treaty of 1922.

[Pictured: German naval personnel watching the battleship SMS Hessen, September 1930]

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Library of Congress

1931: Japan violates League of Nations

- Army strength: 140,516 people
- Navy strength: 93,307 people
- Marine Core strength: 16,782 people
- Air Force strength: Not yet formed
- Total strength: 252,605 people
- Percent of population enlisted: 0.20%

The Great Depression's effects continued to spread throughout the world in 1931, increasing tensions at home and abroad. It would be years before the onset of WWII; however, a hint of ensuing international conflict set in when Japanese forces captured Manchuria in violation of the League of Nations in September 1931. The invasion put U.S. Secretary of State Henry L. Stimson in the position of determining a way to thwart the conflict. He issued the Stimson Doctrine in January 1932, which said the U.S. would not honor agreements or treaties between Japan and China that were in violation of existing U.S. rights or agreements.

[Pictured: Henry Stimson, 2nd from right; at the White House, Washington, D.C.]

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U.S. National Archives // Flickr

1932: Military collides with Bonus Marchers

- Army strength: 134,957 people
- Navy strength: 93,384 people
- Marine Core strength: 16,561 people
- Air Force strength: Not yet formed
- Total strength: 244,902 people
- Percent of population enlisted: 0.20%

In the summer of 1932, Congress denied military veterans an immediate bonus payment for participation in WWI. " Bonus Marchers" numbering more than 20,000 remained in Washington after this decision, demonstrating discontent so much that President Hoover called for the Army's help. Hundreds of troops intervened on the marchers’ camps force that left two protesting World War II veterans dead and caused a massive outcry among the American public.

[Pictured: The Bonus Army fights with D.C. police]

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NPS Photo

1933: Civilian Conservation Corps

- Army strength: 136,547 people
- Navy strength: 91,230 people
- Marine Core strength: 16,068 people
- Air Force strength: Not yet formed
- Total strength: 243,845 people
- Percent of population enlisted: 0.19%

A little over three years after the initial stock market crash, the unemployment rate in the U.S. was 24.9%, with almost 15 million U.S. citizens jobless. In response, President Franklin D. Roosevelt started the Civilian Conservation Corps (CCC) as part of his New Deal program. The CCC comprised existing government departments, including the Army, administering voluntary camps that provided more than 3 million men with manual labor jobs, mainly in natural resource conservation. Many Army officers benefitted from overseeing the camps, not otherwise having the opportunity to supervise large groups of personnel in the period between the world wars.

Also in 1933, Adolf Hitler rose to power in Germany.

[Pictured: Members of the Civilian Conservation Corps in the Pacific Northwest]

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U.S.National Archives

1934: U.S. occupation ends in Haiti

- Army strength: 138,464 people
- Navy strength: 92,312 people
- Marine Core strength: 16,361 people
- Air Force strength: Not yet formed
- Total strength: 247,137 people
- Percent of population enlisted: 0.20%

After President Roosevelt established an agreement to disengage from Haiti in 1933, the U.S. occupation of the country officially drew to a close Aug. 1, 1934. This followed FDR's "Good Neighbor" policy, which meant not interfering in Latin American domestic affairs; however, the U.S. did not relinquish its hand in Haitian finances until 1947.

[Pictured: U.S. President Franlink Delano Roosevelt in 1934]

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History.navy.mil

1935: GHQ Air Force and B-17

- Army strength: 139,486 people
- Navy strength: 95,053 people
- Marine Core strength: 17,260 people
- Air Force strength: Not yet formed
- Total strength: 251,799 people
- Percent of population enlisted: 0.20%

Buoyed by advances in aviation and the use of planes in World War I, more than a dozen commissions and boards grappled from 1919 and 1934 to determine how to move forward with military aviation in a way that could be separate from general support aviation by the Army. The Baker Board of 1934 proposed a peacetime air force, established in 1935 as the General Headquarters (GHQ) Air Force and based at Langley Field, Va. The GHQ Air Force would function as a centralized unit for long-distance strikes. As part of this effort, 1935 also marks the unveiling by the Boeing Airplane Co. of the Model 299, a long-range, four-engine heavy bomber that would transform air battles that was eventually coined the “ B-17 Flying Fortress.”

[Pictured: Machine-gun crew abord the USS Ranger, October 8, 1935. ]

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Three Lions // Getty Images

1936: Abraham Lincoln Brigade

- Army strength: 167,816 people
- Navy strength: 106,292 people
- Marine Core strength: 17,248 people
- Air Force strength: Not yet formed
- Total strength: 291,356 people
- Percent of population enlisted: 0.23%

International governments looked upon the Spanish Civil War with trepidation, worried escalation could lead to a larger-scale, world war. To prevent higher stakes, a number of Western governments including the United States signed a non-intervention treaty. That didn’t stop roughly 35,000 volunteers from 50 countries—including 2,800 U.S. volunteers—from traveling to Spain in 1936 to fight for the Spanish Republic against a fascist uprising aided by Hitler and Mussolini. American volunteers named their units the John Brown Battery, Abraham Lincoln Battalion, and George Washington Battalion. These units, along with volunteers from Britain, Canada, and several other countries, formed the Fifteenth Unit Brigade, known colloquially as the Abraham Lincoln Brigade.

[Pictured: Refugees from the Spanish Civil War cross into France]

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The National Guard

1937: Protective Mobilization Plan

- Army strength: 179,968 people
- Navy strength: 113,617 people
- Marine Core strength: 18,223 people
- Air Force strength: Not yet formed
- Total strength: 311,808 people
- Percent of population enlisted: 0.24%

As the U.S. began to concentrate its economic power toward mobile war operations, the government enacted the Protective Mobilization Plan, in which the National Guard would be inducted into federal service. This gave the Army a protective force of 400,000 troops, which could protect the nation while the Army focused on expansion and training. These plans were the foundation for the mobilization of troops in the summer of 1940, not long before the U.S. entered WWII.

[Pictured: Soldiers from the 118th Infantry Regiment, 30th Infantry Division, South Carolina National Guard]

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Norman Smith/Fox Photos/Getty Images

1938: Munich Agreement inspires U.S. hemisphere defense strategy

- Army strength: 185,488 people
- Navy strength: 119,088 people
- Marine Core strength: 18,356 people
- Air Force strength: Not yet formed
- Total strength: 322,932 people
- Percent of population enlisted: 0.25%

The Munich Agreement (also called the “Munich Betrayal”) in September 1938 was a settlement between Italy, Germany, and France allowing Germany to annex the Sudetenland in western Czechoslovakia, just four months after it became public knowledge that Hitler intended to occupy all of that country. The pact prevented all-out war but ceded a significant part of Czechoslovakia to German rule. As the American military watched things unfold overseas and noted the advances worldwide in war technology and artillery reach, it adjusted its defense strategy to focus on protecting the Western Hemisphere from enemy fire nad hostile air bases in what has been coined the “ hemisphere defense.”

[Pictured: A British army sentry on duty beside Spanish gendarmes during the Spanish Civil War]

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Hans Sönnke // Wikimedia Commons

1939: World War II officially begins

- Army strength: 189,839 people
- Navy strength: 125,202 people
- Marine Core strength: 19,432 people
- Air Force strength: Not yet formed
- Total strength: 334,473 people
- Percent of population enlisted: 0.26%

World War II officially began with Germany’s invasion of Poland, followed two days later by the U.K. and France declaring war on Germany. Although the U.S. remained neutral until 1941, the military was still taking measures to train and plan for mobilization. FDR in 1939 proposed the Cash and Carry policy which replaced the 1936 Neutrality Acts and allowed the sale of military technology and materials to nations at war.

[Pictured: German soldiers at the border of Poland in 1939]

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National Archives

1940: U.S. prepares for war

- Army strength: 269,023 people
- Navy strength: 160,997 people
- Marine Core strength: 28,345 people
- Air Force strength: Not yet formed
- Total strength: 458,365 people
- Percent of population enlisted: 0.35%

American involvement in WWII was limited: The military contributed materials and financial support to Great Britain, the Republic of China, and the Soviet Union. Expecting eventual involvement, however, the U.S. was also beginning to strengthen its own military forces. From June of 1940 through December of 1941, $36 billion was allocated to the War Department (more than was spent on all of World War I) and $8 billion for the Army alone. Meanwhile, the munitions program was preparing weaponry to sustain a military force of more than 1 million men.

[Pictured: Smoke rising from the London docks after an air raid during the Blitz, 1940]

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U.S. Archives

1941: U.S. enters WWII

- Army strength: 1,462,315 people
- Navy strength: 284,427 people
- Marine Core strength: 54,359 people
- Air Force strength: Not yet formed
- Total strength: 1,801,101 people
- Percent of population enlisted: 1.35%

The U.S. declared war on Japan on Dec. 8, 1941, following the Japanese bombing of Pearl Harbor. Japan’s attack lasted just one hour and 15 minutes but managed to inflict heavy damage upon the U.S. Pacific fleet, including killing 2,403 people (68 of whom were civilians), disabling 112 watercraft and 164 aircraft, and sinking six battleships. The USS Arizona is still on the ocean floor of Pearl Harbor with entire crew on board.

Three days after declaring war on Japan, the U.S. declared war on Germany and Italy.

[Pictured: USS Shaw exploding at Pearl Harbor, December 7, 1941]

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Public Domain

1942: War with Bulgaria, Hungary, and Romania

- Army strength: 3,075,608 people
- Navy strength: 640,570 people
- Marine Core strength: 142,613 people
- Air Force strength: Not yet formed
- Total strength: 3,858,791 people
- Percent of population enlisted: 2.86%

The U.S. officially declared war on Bulgaria, Hungary, and Romania on June 5, 1942. The American government spent colossal amounts of money on the effort and assumed a wartime economy. American businesses, farmers, and factory workers all contributed. Toward the end of the year, it was mandatory for all men between the ages of 18 and 64 to register for the draft, though many volunteered before being called. U.S. troops inflicted critical damage on a Japanese naval fleet in the Battle of Midway in June 1942.

With involvement in World War II escalating, rationing of foods such as sugar, meat, and coffee, began.

[Pictured: A ship is destroyed in the battle Midway in june of 1942]

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Public Domain

1943: Eisenhower chosen to lead Allies

- Army strength: 6,994,472 people
- Navy strength: 1,741,750 people
- Marine Core strength: 308,523 people
- Air Force strength: Not yet formed
- Total strength: 9,044,745 people
- Percent of population enlisted: 6.61%

Gen. Dwight David Eisenhower in 1915 graduated from the U.S. Military Academy at West Point, just three years before World War I began. He worked up through the ranks from infantryman to captain, instructor, major, and lieutenant colonel before the first world war drew to a close. By the time the second war rolled around, Eisenhower had worked in varying capacities such as an instructor. football coach, and assistant to Gen. MacArthur; and graduated from Army War College, Fort McNair, Washington D.C., and first in his class from Command and General Staff School in Fort Leavenworth, Kansas. On Feb. 11, 1943, the future U.S. president was appointed Supreme Commander of Allied Expeditionary Forces to command the Operation Overlord, which kicked off by invading Italy that year.

[Pictured: A fleet of B-24s flies above the destruction in Europe.]

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Public Domain

1944: D-Day

- Army strength: 7,994,750 people
- Navy strength: 2,981,365 people
- Marine Core strength: 475,604 people
- Air Force strength: Not yet formed
- Total strength: 11,451,719 people
- Percent of population enlisted: 8.27%

In the early morning of June 6, 1944, Allied troops enacted D-Day, which would bring the war about-face and bring down Nazi Germany. Approximately 155,000 Allied troops comprising U.S., British, and Canadian soldiers stormed Omaha Beach in Normandy, France.

[Pictured: Allied troops in the Battle of Normandy]

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Public Domain

1945: Battle of Iwo Jima

- Army strength: 8,266,373 people
- Navy strength: 3,319,586 people
- Marine Core strength: 469,925 people
- Air Force strength: Not yet formed
- Total strength: 12,055,884 people
- Percent of population enlisted: 8.62%

Among dozens of significant battles throughout World War II was the Battle of Iwo Jima, during which time the Japanese island of Iwo Jima was taken over by the U.S. Marine Corps and Navy. After the invasion of Germany, WWII officially ended when President Truman ordered the atomic bombs to be dropped on Japan in August 1945. Overall, the U.S. suffered almost half a million military and civilian casualties during the war, and the government spent about $4.1 trillion in modern dollars—making it the most expensive war in U.S. history.

[Pictured: Atomic cloud over Hiroshima, Japan]

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Public Domain

1946: First session of the United Nations

- Army strength: 1,435,496 people
- Navy strength: 978,203 people
- Marine Core strength: 155,679 people
- Air Force strength: 455,515 people
- Total strength: 3,024,893 people
- Percent of population enlisted: 2.14%

The U.S. military continued to demobilize in 1946, but slowed down the recovery of troops to fulfill outstanding obligations overseas. This decision resulted in protests from countries like China and France that did not subside until more than half of American troops returned home. The newly formed United Nations General Assembly had its first meeting in February 1946 at the Methodist Central Hall in London. The goal of the international organization was to encourage cooperation between countries and avoid another conflict like World War I and II. Its headquarters would be built in lower Manhattan in 1948, thanks to an $8.5 million donation from John D. Rockefeller to purchase a parcel previously occupied by a slaughterhouse.

[Pictured: World War II Bond Rally, Navy Yard, Mare Island, Ca]

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Public Domain

1947: Air Force, National Security Council founded, Cold War erupts

- Army strength: 685,458 people
- Navy strength: 497,773 people
- Marine Core strength: 93,053 people
- Air Force strength: 305,827 people
- Total strength: 1,582,111 people
- Percent of population enlisted: 1.10%

As post-war demobilization continued, the conversation of how the military would organize itself helped to create in 1947 the United States Air Force and National Security Council. The council spawned the Central Intelligence Agency and Department of Defense. Post-war tensions between the Soviet Union and U.S. had officially manifested as the Cold War. To contain the spread of communism, President Truman facilitated the Truman Doctrine March 29, 1947, which transferred $400 million to Turkey and Greece to aid in the fight against communism.

[Pictured: U.S. President Harry S. Truman]

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Library of Congress

1948: Marshall Plan signed to rebuild Europe

- Army strength: 554,030 people
- Navy strength: 417,535 people
- Marine Core strength: 84,988 people
- Air Force strength: 387,730 people
- Total strength: 1,444,283 people
- Percent of population enlisted: 0.98%

The Army's chief responsibilities as part of the National Security Act were to carry out land operations, prove anti-aircraft units, and supply occupation and security garrisons for use overseas. The Navy continued to control the Marine Corps, and the new Air Force commanded strategic air warfare and combat air backup for the Army. President Truman signed the Marshall Plan on April 3, 1948, which allowed the U.S. to provide more than $12 million to help rebuild western European economies. Congress passed a law declaring the Civil Air Patrol as the official civilian backup of the U.S. Air Force. Finally, on July 26, 1948, Truman passed Executive Order 9981 ending racial segregation in the U.S. Armed Forces.

[Pictured: Tuskegee Airmen in World War II]

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Abbie Rowe // Wikimedia Commons

1949: North Atlantic Treaty

- Army strength: 660,473 people
- Navy strength: 447,901 people
- Marine Core strength: 85,965 people
- Air Force strength: 419,347 people
- Total strength: 1,613,686 people
- Percent of population enlisted: 1.08%

An amendment to the National Security Act in 1949 transformed the National Military Establishment into an executive entity, also known as the Department of Defense, comprising the Army, Navy, and Air Force. The North Atlantic Treaty was signed in April 1949, establishing the intergovernmental military alliance known as NATO. The Cold War installment known as the Revolt of the Admirals also took place in 1949, during which retired and active Navy admirals alike publicly disagreed with President Truman on the subject of strategic nuclear bombing as the primary mode of national defense. Additionally, a “Red Scare” broke out in the U.S. during which several public figures were named in an FBI report as Communist Party members, including Helen Keller and Dorothy Parker.

[Pictured: President Truman signing the document implementing the North Atlantic Treaty in the Oval office]

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Public Domain

1950: Koren War begins

- Army strength: 593,167 people
- Navy strength: 380,739 people
- Marine Core strength: 74,279 people
- Air Force strength: 411,277 people
- Total strength: 1,459,462 people
- Percent of population enlisted: 0.96%

The Korean War touched off on June 25, 1950, when roughly 75,000 North Korean People’s Army soldiers crossed the boundary between North and South Korea. The war on the Korean peninsula would last for three years without ever being officially declared and cost 36,914 lives. Original estimates following the war’s conclusion put the death toll at 54,260; a number revised to reflect that was actually the total of all U.S. military deaths around the world during between 1950 and 1953.

[Pictured: U.S. military forces enter into a three-year undeclared war on the Korean peninsula.]

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Public Domain

1951: Second capture of Seoul, Treaty of San Francisco

- Army strength: 1,531,774 people
- Navy strength: 736,596 people
- Marine Core strength: 192,620 people
- Air Force strength: 788,381 people
- Total strength: 3,249,371 people
- Percent of population enlisted: 2.10%

As the Korean War waged on, United Nations soldiers liberated Seoul for a second time in March 1951. Later that year, the U.N. and communist North Korean forces engaged in truce talks. A second Red Scare emerged when Ethel and Julius Rosenberg were convicted of conspiracy to commit espionage and received the death penalty. As part of the Treaty of San Francisco, 49 countries signed a peace treaty in 1951 with Japan.

[Pictured: 159th Artillery Battalion, 24th Infantry Regiment]

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USAF // Wikimedia Commons

1952: First hydrogen bomb detonated

- Army strength: 1,596,419 people
- Navy strength: 824,265 people
- Marine Core strength: 231,967 people
- Air Force strength: 983,261 people
- Total strength: 3,635,912 people
- Percent of population enlisted: 2.31%

The Treaty of San Francisco went into effect in 1952, officially ending the U.S. occupation of Japan. As nuclear testing continued, the U.S. military successfully detonated the first hydrogen bomb as part of Operation Ivy. That nuclear test still stands as the fourth largest for all U.S. tests of that kind. Meanwhile, President Eisenhower traveled to Korea to explore methods of ending the war.

[Pictured: Col James K. Johnson, 4FIW Commander, with President Eisenhower during inspection tour at Kimpo AB, Korea December, 1952]

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Public Domain

1953: Korean Armistice Agreement

- Army strength: 1,533,815 people
- Navy strength: 794,440 people
- Marine Core strength: 249,219 people
- Air Force strength: 977,593 people
- Total strength: 3,555,067 people
- Percent of population enlisted: 2.22%

The U.N., China, and North Korea on July 27, 1953, collectively engaged in an armistice to end the Korean War and pull troops out of both countries. The agreement was signed by U.S. Army Lt. Gen. William K. Harrison Jr. from the UN Command Delegation and North Korean Gen. Nam II, representing North Korea and China.

Elsewhere, the CIA and British Secret Intelligence Service collaboratively overthrew democratically elected Iranian Prime Minister Mohammad Mosaddegh in a coup d'etat when they learned of his involvement with the communist pro-Soviet Tudeh Party.

[Pictured: General Mark W. Clark signs the Korean armistice agreement on July 27, 1953 ]

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U.S. Air Force

1954: U.S. Air Force Academy established

- Army strength: 1,404,598 people
- Navy strength: 725,720 people
- Marine Core strength: 223,868 people
- Air Force strength: 947,918 people
- Total strength: 3,302,104 people
- Percent of population enlisted: 2.03%

Despite having authorized hundreds of millions of dollars of military budget aid to Vietnam, President Eisenhower advised against U.S. assisting the French in its continued conflict with Viet Minh. Eisenhower also approved the establishment of the U.S. Air Force Academy in Colorado. The U.S. Army was investigated by Sen. Joseph McCarthy for allegedly not cracking down hard enough on communism.

[Pictured: Basic cadets from the first Air Force Academy class line up for physical training]

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Hulton Archive // Getty Images

1955: Navy helps evacuate Chinese Nationalist soldiers

- Army strength: 1,109,296 people
- Navy strength: 660,695 people
- Marine Core strength: 205,170 people
- Air Force strength: 959,946 people
- Total strength: 2,935,107 people
- Percent of population enlisted: 1.77%

As the conflict in Vietnam escalated, President Eisenhower sent U.S. advisors to South Vietnam when Prime Minister Ngo Dinh Diem received threats from multiple domestic sources. Also that year, the U.S. Navy helped the Republic of China evacuate Chinese Nationalist soldiers and residents from the Tachen Islands when the People's Liberation Army overtook the area. The Formosa Resolution detailed U.S. protection of the Republic of China from the People's Republic of China.

[Pictured: Civilians crowd onto the pier of the Tachen Islands awaiting evacuation by the landing craft of the Seventh Fleet of the US Navy]

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Zsolt Házy // Wikimedia Commons

1956: Hungarian Revolution

- Army strength: 1,025,778 people
- Navy strength: 669,925 people
- Marine Core strength: 200,780 people
- Air Force strength: 909,958 people
- Total strength: 2,806,441 people
- Percent of population enlisted: 1.66%

The Hungarian Revolution of 1956 began with an organized group of student protesters marching through the streets of Budapest Oct. 23 with loudspeakers, chanting “This we swear, this we swear, that we will no longer be slaves.” After reading an anti-communist proclamation demanding an independent Hungary, students stormed the radio building near the Hungarian Parliament, prompting police to open fire. The violence killed one student and marked the first bloodshed in the revolution that ultimately toppled the Soviet government.

The violent outbreak turned the protest into an all-out nationwide revolt against Soviet policies that were being forced on the public by the Hungarian People’s Republic. The uprising exploded with militias fighting the military, arming prisoners, and a death toll that included 2,500 Hungarians and 700 Soviet troops. Another 200,000 Hungarians fled as refugees. Meanwhile in the United States, officials and military leaders stood by watching events unfold, too afraid of another world war (or disrupting recently improved diplomacy with Moscow) to step in and assist the protestors. The revolution was squashed Nov. 4 when the Soviet Union sent soldiers into Hungary, causing an uproar by U.S. citizens and Hungarian demonstrators over the controversial lack of action by the U.S., which had gone so far as to utilize the CIA-run Radio Free Europe (RFE) to broadcast encouragement to the rebels, imply the U.S. would be arriving with help, and offer tactical insights for fighting the Soviets.

Ultimately, the Soviet Union would not regain governmental control over Hungary again.

[Pictured: Street corner in Budapest during the revolution]

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U.S. Fish and Wildlife Service

1957: Distant Early Warning Sign

- Army strength: 997,994 people
- Navy strength: 676,071 people
- Marine Core strength: 200,861 people
- Air Force strength: 919,835 people
- Total strength: 2,794,761 people
- Percent of population enlisted: 1.63%

Although the U.S. and Soviet Union vowed to proceed in the Cold War without engaging in full-on nuclear confrontation, the U.S. partnered with Canada to begin construction on the Distant Early Warning Line in 1954. This radar network, which became functional in 1957, was able to detect early signs of missile or air attacks coming from the north.

[Pictured: Aerial view of U.S. Air Force DEW Line and White Alice station, Grant Point, Izembek ]

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Thomas J. O'Halloran // Wikimedia Commons

1958: Lebanon crisis

- Army strength: 898,925 people
- Navy strength: 639,942 people
- Marine Core strength: 189,495 people
- Air Force strength: 871,156 people
- Total strength: 2,599,518 people
- Percent of population enlisted: 1.49%

The Lebanon Crisis broke out in 1958, caused by the threat of civil war between Maronite Christians and Muslims. U.S. Marines helped diffuse the situation as part of Operation Blue Bat, to help strengthen the pro-Western government under President Camille Chamoun and protect it from Syrian and Egyptian threats.

[Pictured: July 1958 - U.S. Marine sits in a foxhole in Lebanon]

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U.S. Army // Wikimedia Commons

1959: U.S. Special Forces train soldiers in Laos

- Army strength: 861,964 people
- Navy strength: 625,661 people
- Marine Core strength: 175,571 people
- Air Force strength: 840,435 people
- Total strength: 2,503,631 people
- Percent of population enlisted: 1.41%

Cold War tensions continued to mount when a Communist group in Laos overtook several provinces bordering North Vietnam and China. Neither side prevailed, despite the U.S. military intervention, training of Laotian soldiers, and growing presence there since 1957 in support of Royal Lao Armed Forces (known commonly by its French acronym, FAR).

[Pictured: Pathet Lao, a communist organization in Laos, circa 1953]

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Public Domain // Wikimedia Commons

1960: U.S.-Cuba standoff

- Army strength: 873,078 people
- Navy strength: 616,987 people
- Marine Core strength: 170,621 people
- Air Force strength: 814,752 people
- Total strength: 2,475,438 people
- Percent of population enlisted: 1.37%

The U.S. acknowledged Fidel Castro as the leader of Cuba, but as Castro—who rose to power in 1959 following an armed uprising that unseated Cuban dictator Fulgencio Batista—increasingly nationalized U.S. companies and investments there, harsh penalties were enacted. The U.S. in 1960 suspended sugar imports from Cuba, dissolved ties to the Castro government, and halted all Cuban assets at home. In March of 1960, President Dwight D. Eisenhower directed the CIA to start training of Cuban exiles to overthrow Castro and allocated $13.1 million to the cause.

[Pictured: March 1960 - Fidel Castro, Che Guevara and others marching through the streets in protest over the La Coubre explosion]

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Keystone // Getty Images

1961: Bay of Pigs

- Army strength: 858,622 people
- Navy strength: 626,223 people
- Marine Core strength: 176,909 people
- Air Force strength: 821,151 people
- Total strength: 2,482,905 people
- Percent of population enlisted: 1.35%

Though the threat of nuclear war remained low, newly appointed President John F. Kennedy nevertheless vowed to equip the U.S. military with the necessary means to retaliate if attacked. Kennedy warned the Soviet Union against getting involved in the U.N. establishment of peace and independence in the Congo. The Bay of Pigs invasion took place in Cuba on April 17, 1961, sending almost 1,500 trained Cuban exiles storming the Bay of Pigs beaches. The initial air strike on Cuba’s airfield didn’t dismantle the entire air force, however, ultimately causing a failed attempt to overthrow the growing Communist government.

[Pictured: Cuban Revolutionary Army celebrating their victory in the Bay of Pigs Invasion]

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/AFP // Getty Images

1962: Cuban Missile Crisis

- Army strength: 1,066,404 people
- Navy strength: 664,212 people
- Marine Core strength: 190,962 people
- Air Force strength: 884,025 people
- Total strength: 2,805,603 people
- Percent of population enlisted: 1.50%

When it was revealed that Cuba was in possession of Soviet ballistic missiles, the U.S. government set up a naval blockade in southern Florida. This 13-day incident became known as the Cuban Missile Crisis. President Kennedy warned the Soviet Union that if they launched missiles from Cuba against any country, the U.S would be forced to use nuclear weapons on Russia. The issue was resolved when Soviet leader Khrushchev called for the removal of the Soviet missiles from Cuba.

[Pictured: US President John Fitzgerald Kennedy signs the order of naval blockade of Cuba on October 24, 1962 during the Cuban missiles crisis]

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Public Domain // Wikimedia Commons

1963: Limited Nuclear Test Ban Treaty

- Army strength: 975,916 people
- Navy strength: 663,897 people
- Marine Core strength: 189,683 people
- Air Force strength: 869,431 people
- Total strength: 2,698,927 people
- Percent of population enlisted: 1.43%

Representatives from the Soviet Union, Great Britain, and the United States on Oct. 7, 1963, signed the Limited Nuclear Test Ban Treaty. The document effectively banned nuclear testing in space, underwater, and in the atmosphere, but did allow for testing in underground sites with responsible containment of radioactive material.

[Pictured: October 7,1963 - President Kennedy signs the Limited Nuclear Test Ban Treaty]

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No Author Provided // Wikimedia Commons

1964: Gulf of Tonkin

- Army strength: 973,238 people
- Navy strength: 665,969 people
- Marine Core strength: 189,777 people
- Air Force strength: 856,798 people
- Total strength: 2,685,782 people
- Percent of population enlisted: 1.40%

As Saigon's government continued to decline, President Lyndon B. Johnson sent military advisors to South Vietnam to assist. U.S. destroyers in the Tonkin Gulf in August 1964 radioed that they were receiving fire by North Vietnamese forces, inspiring President Johnson to request increased military force in Indochina. Congress drew up the Tonkin Gulf Resolution, which gave the green light for any means necessary to stave off attacks and halt further violence and ultimately managed to intensify the conflict in Vietnam.

[Pictured: President Johnson during a speech, 1964]

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manhhai // Flickr

1965: U.S. officially enters Vietnam War

- Army strength: 969,066 people
- Navy strength: 669,985 people
- Marine Core strength: 190,213 people
- Air Force strength: 824,662 people
- Total strength: 2,653,926 people
- Percent of population enlisted: 1.37%

As the 9th Marine Expeditionary Brigade arrived on the shores of China Beach on March 8, 1965, the U.S. officially entered the Vietnam War. Prior activity in Vietnam—including 23,000 military advisors already there and various naval action—did not include active fighting and was being used largely for support and intelligence. Throughout the Vietnam Era, more 2,709,918 Americans—9.7% of their generation—served in Vietnam.

[Pictured: U.S. Army helicopters in Vietnam in 1965 ]

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Tommy Truong79 // Flickr

1966: House Un-American Activities Committee

- Army strength: 1,199,784 people
- Navy strength: 743,322 people
- Marine Core strength: 261,716 people
- Air Force strength: 887,353 people
- Total strength: 3,092,175 people
- Percent of population enlisted: 1.57%

The House Un-American Activities Committee (HUAC) was an investigative committee within the U.S. House of Representatives that was founded in 1938 to investigate potential disloyal American citizens. HUAC in 1966 began hearings to investigate citizens alleged to be helping the Viet Cong as well as anti-war activists. Hundreds of protesters showed up to the hearings on the first day, Aug. 16, 1966, while witnesses resisted their questioners. The hearings and protests incited more anti-Vietnam War demonstrations around the country.

[Pictured: People protesting the Vietnam War in downtown Philadelphia, Pa, March, 26 1966]

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Defense Dept. photo // Wikimedia Commons

1967: Operation Swift

- Army strength: 1,442,498 people
- Navy strength: 750,224 people
- Marine Core strength: 285,269 people
- Air Force strength: 897,494 people
- Total strength: 3,375,485 people
- Percent of population enlisted: 1.70%

U.S. Marines carried out Operation Swift beginning Sept. 4, 1967, in order to free two Marine companies that had been waylaid by the Peoples Army of Vietnam. The rescue mission, involving three 5th Marine Regiment battallions up against bigger forces of NVA and Viet Cong, took place in the Quang Nam and Quang Tin provinces and resulted in two Medal of Honor recipients, the saving of the city of Da Nang, and an estimated enemy casualty count surpassing 4,000.

[Pictured: A U.S. Marine rests during Operation Swift ]

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U.S. Army photo

1968: Tet Offensive

- Army strength: 1,570,343 people
- Navy strength: 763,626 people
- Marine Core strength: 307,252 people
- Air Force strength: 904,850 people
- Total strength: 3,546,071 people
- Percent of population enlisted: 1.77%

A coordinated 1968 attack during the Tet holiday by North Vietnamese and communist Viet Cong forces (called the Tet Offensive) resulted in extensive casualties. The attack came at a time when the United States was claiming the war was all but won, ensuring a further dropout of support for the Vietnam War by the American public.

[Pictured: The 47th Infantry Regiment takes the offensive May 1968 in south Saigon during the Tet Offensive]

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manhhai // Flickr

1969: Nixon Doctrine

- Army strength: 1,512,169 people
- Navy strength: 773,779 people
- Marine Core strength: 309,771 people
- Air Force strength: 862,353 people
- Total strength: 3,458,072 people
- Percent of population enlisted: 1.71%

Newly appointed President Richard Nixon established the Nixon Doctrine (first called the Guam Doctrine) in 1969. This document established that the U.S. would rely on its Asian allies to take control of their own military defenses, while still receiving some support from their American neighbors.

[Pictured: July 30, 1969 - Nixon visits South Vietnam ]

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Public Domain // Wikimedia Commons

1970: U.S. troops invade Cambodia

- Army strength: 1,322,548 people
- Navy strength: 691,126 people
- Marine Core strength: 259,737 people
- Air Force strength: 791,349 people
- Total strength: 3,064,760 people
- Percent of population enlisted: 1.49%

As the Vietnam War began to wind down, U.S. troops invaded Cambodia in 1970 to capture lingering Viet Cong forces and prevent North Vietnamese attacks on South Vietnam. On April 30 President Nixon gave a speech explaining his decision, which touched off a fresh set of anti-war protests that resulted in the notorious Kent State shootings where four protestors were killed and nine injured.

[Pictured: President Nixon delivers a speech to the American people announcing the Cambodian incursion]

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Tommy Truong79 // Flickr

1971: Conviction in My Lai Massacre

- Army strength: 1,123,810 people
- Navy strength: 621,565 people
- Marine Core strength: 212,369 people
- Air Force strength: 755,300 people
- Total strength: 2,713,044 people
- Percent of population enlisted: 1.31%

Army Lieut. William Calley was convicted of the 1968 deaths of 22 civilians during the My Lai Massacre, in which more than 500 people were killed. He was sentenced to life in prison, but President Richard Nixon reduced his sentence and Calley ended up serving just three years under house arrest.

[Pictured: Army Lieut. William Calley is accused of killing 102 civilians in the Mai Lai Massacre]

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manhhai // Flickr

1972: Nguyen Hue Offensive

- Army strength: 810,960 people
- Navy strength: 586,923 people
- Marine Core strength: 198,238 people
- Air Force strength: 725,838 people
- Total strength: 2,321,959 people
- Percent of population enlisted: 1.11%

The North Vietnamese launched the Easter Offensive (dubbed the Nguyen Hue Offensive) on March 30, 1972, which was a large-scale, three-part assault on South Vietnam. Hundreds of South Vietnamese civilians and soldiers were injured as a result, but the attack was ultimately stopped in October of that year by South Vietnamese soldiers and U.S. advisers.

[Pictured: Helicopters of the U.S. 229th Aviation Battalion, 3rd Brigade, First Air Cavalry Division, land in formation at Lai Khe during the Easter Offensive]

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U.S. Air Force

1973: Ceasefire signed

- Army strength: 800,973 people
- Navy strength: 563,683 people
- Marine Core strength: 196,098 people
- Air Force strength: 691,182 people
- Total strength: 2,251,936 people
- Percent of population enlisted: 1.06%

President Nixon announced progress in peace negotiations with Vietnam, and called for the cessation of offensive action in North Vietnam. A ceasefire was signed, but soon violated by the communists in March of 1973. All-out war had resumed by 1974.

[Pictured: Januar 27, 1973 - President Nixon signing the peace agreement]

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National Archives & Records Administration // WIkimedia Commons

1974: U.S. evacuation of Cyprus

- Army strength: 783,330 people
- Navy strength: 545,903 people
- Marine Core strength: 188,802 people
- Air Force strength: 643,970 people
- Total strength: 2,162,005 people
- Percent of population enlisted: 1.01%

As President Nixon faced the final throes of the Watergate scandal back home, Turkey invaded Cyprus in July of 1974. Following the invasion, the U.S. Navy swooped in to evacuate almost American citizens from the island country to Beirut. The following month, Nixon resigned from his presidency.

[Pictured: President Nixon during the broadcast of his address to the nation]

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-/AFP // Getty Images

1975: End of Vietnam War

- Army strength: 784,333 people
- Navy strength: 535,085 people
- Marine Core strength: 195,951 people
- Air Force strength: 612,751 people
- Total strength: 2,128,120 people
- Percent of population enlisted: 0.99%

The Vietnam War ended on April 30, 1975, with the fall of Saigon (now called Ho Chi Minh City). Communist North Vietnamese and Viet Cong troops overtook the city, causing American and South Vietnamese forces to evacuate and South Vietnam to surrender.

[Pictured: Aprile 30, 1975 - A Vietcong tank in front of the presidential palace of the US-backed Southern Vietnamese regime in Saigon on the day that the city fell to communist troops]

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Department of Defense

1976: Women admitted to service academies

- Army strength: 779,417 people
- Navy strength: 524,678 people
- Marine Core strength: 192,399 people
- Air Force strength: 585,416 people
- Total strength: 2,081,910 people
- Percent of population enlisted: 0.95%

This year in military history was significant for women in the military, marking the first time they were admitted to service academies. More than 300 women entered, including 119 women at West Point alone.

[Pictured: Women in the Air Force, or WAFs, and staff at the I.G. Brown Training and Education Center on McGhee Tyson Air National Guard Base in Louisville, TN]

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Public Domain

1977: President Carter’s new foreign policy for Latin America

- Army strength: 782,246 people
- Navy strength: 529,895 people
- Marine Core strength: 191,707 people
- Air Force strength: 570,695 people
- Total strength: 2,074,543 people
- Percent of population enlisted: 0.94%

In response to President Jimmy Carter's new foreign policy outlined for Latin America (namely ending U.S. intervention there and protecting human rights), Nicaraguan military leader Anastasio Somoza rescinded a state of siege that had been enforced for the previous three years. This move paved the way for a $2.5 million military aid agreement between the United States and Nicaragua.

[Pictured: President Jimmy Carter at his desk in the Oval Office, 1977]

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U.S. Army

1978: Women’s Army Corps dissolved

- Army strength: 771,624 people
- Navy strength: 529,557 people
- Marine Core strength: 190,815 people
- Air Force strength: 569,712 people
- Total strength: 2,061,708 people
- Percent of population enlisted: 0.93%

The Women's Army Corps was dissolved in 1978, and all women soldiers were incorporated into previously all-male units. There were a few caveats, namely that women were still not allowed to serve in combat positions.

[Pictured: Women's Army Corps members run an obstacle course during basic training]

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Public Domain

1979: Iranian Hostage Crisis

- Army strength: 758,852 people
- Navy strength: 523,335 people
- Marine Core strength: 185,250 people
- Air Force strength: 559,455 people
- Total strength: 2,026,892 people
- Percent of population enlisted: 0.90%

On Nov. 4, 1979, Iranian students overtook the U.S. Embassy in Tehran and held more than 50 Americans hostage. The Iran Hostage Crisis would go on for 444 days.

[Pictured:Two American hostages during the siege of the U.S. Embassy]

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Trikosko/Marion S. // Wikimedia Commons

1980: Failed attempt to end hostage crisis

- Army strength: 777,036 people
- Navy strength: 527,153 people
- Marine Core strength: 188,469 people
- Air Force strength: 557,969 people
- Total strength: 2,050,627 people
- Percent of population enlisted: 0.90%

In April of 1980, several U.S. transport planes and helicopters tried unsuccessfully to rescue Americans being held in the Iranian Hostage Crisis, prompting President Carter to discontinue diplomatic relations with Iran.The botched attempt left one Iranian civilian and eight members of the U.S. military dead. In June of that year, Carter signed Proclamation 4771, which required men between 18 and 26 to "present themselves to register" for the military. Carter insisted this registration was not a draft.

[Pictured: President Jimmy Carter announces new sanctions against Iran in retaliation for taking U.S. hostages]

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Public Domain

1981: Gulf of Sidra Incident

- Army strength: 781,419 people
- Navy strength: 540,219 people
- Marine Core strength: 190,620 people
- Air Force strength: 570,302 people
- Total strength: 2,082,560 people
- Percent of population enlisted: 0.91%

During the Gulf of Sidra Incident, Libya claimed the region as part of its territorial waters. In response, the U.S. engaged in the Freedom of Navigation operations around the gulf, on the grounds that it was legally considered an international body of water. Forces shot down two Libyan fighter jets.

[Pictured: 1981 - A U.S. Navy McDonnell F-4J Phantom II of Fighter Squadron VF-74 Be-Devilers escorting a Libyan Mikoyan-Gurevich MiG-23 over Gulf of Sidra]

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James Case // Wikimedia Commons

1982: Lebanese Civil War

- Army strength: 780,391 people
- Navy strength: 552,996 people
- Marine Core strength: 192,380 people
- Air Force strength: 582,845 people
- Total strength: 2,108,612 people
- Percent of population enlisted: 0.91%

Eight hundred U.S. Marines were sent to Beirut in 1982 during the Lebanese Civil War, along with multinational forces, to take out members of the Palestinian Liberation Organization. The Vietnam Veterans Memorial was also dedicated in Washington D.C. this year with thousands of former and current soldiers attending the event.

[Pictured: 1982 - US Navy Amphibian arriving in Beirut]]

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Cpl. Mauricio Campino // Department of Defense

1983: Peace agreement with Lebanon

- Army strength: 779,643 people
- Navy strength: 557,573 people
- Marine Core strength: 194,089 people
- Air Force strength: 592,044 people
- Total strength: 2,123,349 people
- Percent of population enlisted: 0.91%

In May of 1983, the U.S. signed an agreement requiring Israel to withdraw troops from Lebanon. Negotiations between Israel and Lebanon occured over the course of 35 different sessions that began the previous December. The agreement came following a 1982 invasion of Lebanon by Israel that surrounded Lebanon.

That October, a truck bomb within a marine compound in Beirut killed 241 U.S. personnel that included 220 marines.

[Pictured: Beirut Memorial on Camp Johnson, N.C., erected in honor of the 241 U.S. Marines, sailors, and soldiers who died in a terrorist attack on the Marine Corps barracks in Beirut, Lebanon]

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U.S. Navy // Wikimedia Commons

1984: Marines leave Beirut

- Army strength: 780,180 people
- Navy strength: 564,638 people
- Marine Core strength: 196,214 people
- Air Force strength: 597,125 people
- Total strength: 2,138,157 people
- Percent of population enlisted: 0.91%

Having aided Lebanon during its civil war, the last U.S. Marines withdrew from Beirut in 1984. As the Iran-Iraq War entered in its fourth year, U.S. aerial tanker planes assisted Iranian jets as they were attacked by Saudi Arabian fighter pilots. President Ronald Reagan expressed concern that the incident would worsen the war in the Persian Gulf.

[Pictured: Marines at the port of Beirut on 29 September 1982]

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AFP / Staff // Getty Images

1985: Achille Lauro hijacked

- Army strength: 780,787 people
- Navy strength: 570,705 people
- Marine Core strength: 198,025 people
- Air Force strength: 601,515 people
- Total strength: 2,151,032 people
- Percent of population enlisted: 0.90%

In October of 1985, four Palestinian terrorists hijacked the Italian cruise ship Achille Lauro, killing an American citizen. U.S. Navy pilots later intercepted the Egyptian airliner carrying the terrorists. As part of Cold War negotiations, President Reagan met with Soviet leader Mikhail Gorbachev in Geneva.

[Pictured: Achille Lauro leaves Port Said harbor on October 10, 1985 after Egyptian authorities stopped it from sailing to the Israeli port of Ashdod ]

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Public Domain // Wikicommons

1986: West Berlin Discotheque bombing

- Army strength: 780,980 people
- Navy strength: 581,119 people
- Marine Core strength: 198,814 people
- Air Force strength: 608,199 people
- Total strength: 2,169,112 people
- Percent of population enlisted: 0.90%

The West Berlin Discotheque was bombed in 1986. Three people were killed and more than 200 were injured at the nightclub, which was a popular destination for U.S. soldiers. The attack was traced back to Libyan terrorists. Nine days later, President Reagan approved a series of Air Force, Marine Corps, and Navy airstrikes on Libya.

[Pictured: On April 13, 1986, a crew prepares for an air strike on Libya]

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White House Photographic Office // Wikicommons

1987: Iran-Iraq ceasefire

- Army strength: 780,815 people
- Navy strength: 586,842 people
- Marine Core strength: 199,525 people
- Air Force strength: 607,035 people
- Total strength: 2,174,217 people
- Percent of population enlisted: 0.90%

As violence in the Persian Gulf continued, the U.S. upped its joint military presence in the area and established a policy of confronting passing Kuwaiti oil tankers and accompanying them through the Gulf. A cease-fire between Iran and Iraq later inspired the U.S. to dial down its presence. In December of this 1987, President Reagan and Soviet leader Gorbachev signed the Intermediate-Range Nuclear Forces Treaty in Washington D.C., terminating the use of intermediate and short-range missiles.

[Pictured: On December 8, 1987 President Reagan and General Secretary Gorbachev signed the INF Treaty in the White House ]

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Public Domain // Naval History and Heritage Command photograph

1988: USS Samuel B. Roberts hits naval mine

- Army strength: 771,847 people
- Navy strength: 592,570 people
- Marine Core strength: 197,350 people
- Air Force strength: 576,446 people
- Total strength: 2,138,213 people
- Percent of population enlisted: 0.87%

As part of another installment in the Persian Gulf, the USS Samuel B. Roberts hit a naval mine while on a military operation. The U.S. Navy retaliated by carrying out Operation Praying Mantis, which entailed a series of hits on Iranian oil platforms and naval ships. In December of that year, chairman of the Palestine Liberation Organization, Yasser Arafat, publicly relinquished violence, inspiring the U.S. to initiateconversation with the Palestine Liberation Organization.

[Pictured: On April 14, 1988, Marines inspect an Iranian Sassan oil platform during Operation Praying Mantis]

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George Bush Presidential Library // Wikicommons

1989: Bush-Gorbachev meeting

- Army strength: 769,741 people
- Navy strength: 592,652 people
- Marine Core strength: 196,956 people
- Air Force strength: 570,880 people
- Total strength: 2,130,229 people
- Percent of population enlisted: 0.86%

In September of 1989, President George H.W. Bush called for military advisers and special forces teams to help shut down drug production and trafficking in Colombia, Bolivia, and Peru. Later that year, Bush met with Mikhail Gorbachev off the coast of Malta, and announced the Cold War might be coming to a close.

[Pictured: On December 2, 1989, President Bush met with President Mikhail Gorbachev during the Malta Summit ]

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George Bush Presidential Library // Wikicommons

1990: Chemical Weapons Accord

- Army strength: 732,403 people
- Navy strength: 579,417 people
- Marine Core strength: 196,652 people
- Air Force strength: 535,233 people
- Total strength: 2,043,705 people
- Percent of population enlisted: 0.82%

As part of continued talks, Bush met with Gorbachev to sign the Chemical Weapons Accord, which terminated the production of chemical weapons and called for each party's arsenal to be dismantled. In August of 1990, Iraq invaded Kuwait, sparking the Persian Gulf War. Bush called for a large percentage of the U.S. armed forces to the Persian Gulf to help Saudi Arabia fend off Iraqi forces. In November, the U.N. Security Council passed Resolution 678, which gave the green light for military intervention in Iraq if its government didn't pull forces out of Kuwait by Jan. 15 of the following year.

[Pictured: On June 1, 1990, President George H. W. Bush and President Mikhail Gorbachev sign the Chemical Weapons Accord]

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US Air Force // Wikicommons

1991: Kuwait liberated

- Army strength: 710,821 people
- Navy strength: 570,262 people
- Marine Core strength: 194,040 people
- Air Force strength: 510,432 people
- Total strength: 1,985,555 people
- Percent of population enlisted: 0.78%

On Jan. 17 of 1991, President Bush instructed U.S. armed forces to execute airstrikes against Iraqi forces in Iraq and Kuwait. Later that month, thousands of people convened in Washington D.C. to rally against the Persian Gulf War. The deadliest attack on the U.S. in this war came in late February when an Iraqi scud missile blew up a U.S. barracks in Dhahran, killing 27 soldiers and injuring 98 more. Before the month was over, Saddam Hussein announced that Iraqi soldiers had pulled out of Kuwait. The following day, Bush proclaimed that Kuwait had been liberated. Mikhail Gorbachev stepped down in December of 1991, signalling an end to the Soviet Union and Cold War.

[Pictured: During Operation Desert Storm in 1991, U.S. Air Force aircraft fly over Kuwait]

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U.S. Army photo

1992: Unified Task Force

- Army strength: 610,450 people
- Navy strength: 541,883 people
- Marine Core strength: 184,529 people
- Air Force strength: 470,315 people
- Total strength: 1,807,177 people
- Percent of population enlisted: 0.70%

When Iraq failed to recognize the new border established by the U.N., the U.S. executed a series of military exercises in Kuwait in 1992 to demonstrate preparation for another Iraqi threat. Later that year, the U.N. passed Security Council Resolution 794, ultimately forming the Unified Task Force, whose main responsibility was aiding Somalia in the wake of a humanitarian crisis. That multinational force, led by the U.S., worked from Dec. 5, 1992, to May 4, 1993, in Somalia.

[Pictured: A soldier provides supplies to Somali villagers as part of U.S. humanitarian aid relief efforts in Somalia]

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AFP // Getty Images

1993: Battle of Mogadishu

- Army strength: 572,423 people
- Navy strength: 509,950 people
- Marine Core strength: 178,379 people
- Air Force strength: 444,351 people
- Total strength: 1,705,103 people
- Percent of population enlisted: 0.66%

The U.S. Quick Reaction Forces responded in June 1993 to Somali faction attacks on U.N. forces, and more military operations ensued when U.N. attempts to deliver humanitarian aid were thwarted. That same month, President Bill Clinton called for a cruise missile attack on Iraqi headquarters in Baghdad. The order came in response to a 17-person plot to assassinate former President Bush during his trip to Kuwait in April 1993.

[Pictured: During the Battle of Mogadishu, a jeep burns becuase of a remote controlled bomb]

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MANOOCHER DEGHATI // Getty Images

1994: Iraq Disarmament Crisis

- Army strength: 541,343 people
- Navy strength: 468,662 people
- Marine Core strength: 174,158 people
- Air Force strength: 426,327 people
- Total strength: 1,610,490 people
- Percent of population enlisted: 0.61%

In September of 1994, the Iraq disarmament crisis —which would be used as leverage for the 2003 invasion of Iraq—manifested as Iraq threatening to no longer cooperate with the United Nations Special Commission (UNSCOM) and sending troops near the Iraq-Kuwait border. In return, the U.S. sent soldiers to Kuwait. In October, Iraq pulled its troops out of Kuwait after the U.N. Security Council made further threats.

[Pictured: President Bill Clinton (center) waves to U.S. troops in Kuwait 1994]

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PATRICK HERTZOG // Gety Images

1995: Capt. O’Grady shot down behind enemy lines

- Army strength: 508,559 people
- Navy strength: 434,617 people
- Marine Core strength: 174,639 people
- Air Force strength: 400,409 people
- Total strength: 1,518,224 people
- Percent of population enlisted: 0.57%

As U.S. aircraft assisted in NATO's enforcement of a no-fly zone above Bosnia-Herzegovina, Capt. Scott O'Grady was shot down in his aircraft and rescued about a week later. U.S. fighter planes engaged in NATO strikes against the Bosnian Serb Army, which were threatening areas the U.N. had established as safe zones.

[Pictured: Captain Scott O'Grady (right) at a press conference after being shot down by Bosnian Serbs. He was rescued four days later.]

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ROBERT MILLER // Getty Images

1996: Comprehensive Nuclear-Test Ban Treaty

- Army strength: 491,103 people
- Navy strength: 416,735 people
- Marine Core strength: 174,883 people
- Air Force strength: 389,001 people
- Total strength: 1,471,722 people
- Percent of population enlisted: 0.55%

In the continuation of the Iraq disarmament crisis, Iraq upheld its decision to deny inspectors access to several sites and the U.S. was unable to gain military support to solve the issue. President Clinton gave the go-ahead for U.S. forces to remain in Bosnia as part of NATO's Implementation Force, which sought to maintain peace in Bosnia. Clinton also signed the Comprehensive Nuclear Test Ban Treaty, aimed to put a stop to all nuclear detonations for civil or military means.

[Pictured: Delegates to the United Nations watch the electronic votes to see if the comprehensive global nuclear test-ban treaty would be carried over]

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Public Domain // Wikicommons

1997: Sex scandals plage military

- Army strength: 491,707 people
- Navy strength: 395,564 people
- Marine Core strength: 173,906 people
- Air Force strength: 377,385 people
- Total strength: 1,438,562 people
- Percent of population enlisted: 0.53%

As some U.S. troops remained in Bosnia to maintain peace with the NATO Stabilization Force, a few thousand U.S. soldiers were deployed to nearby Hungary, Croatia, and Italy to provide backup. Back home, sex scandals rocked the military as Army Sergeant Maj. Gene McKinney was accused of sexual misconduct and 12 officers on a training base in Maryland were accused of sexually assaulting women trainees there.

[Pictured: Army Sergeant Maj. Gene McKinney]

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ALEXANDER JOE // Getty Images

1998: U.S. embassies bombed

- Army strength: 484,928 people
- Navy strength: 381,336 people
- Marine Core strength: 173,055 people
- Air Force strength: 367,468 people
- Total strength: 1,406,787 people
- Percent of population enlisted: 0.51%

In August 1998, U.S. embassies in Dar es Salaam, Tanzania, and Nairobi, Kenya, were bombed, killing 224 and injuring more than 5,000. The bombings were linked to Osama bin Laden; al-Qaeda claimed responsibility. In retaliation, the U.S. military dropped cruise missiles on Afghanistan, targeting al-Qaeda camps.

[Pictured: U.S. Secretary of State Madeleine Albright looks at the US embassy in Dar Es Salaam after a bombing which al-Qaeda claimed responsibility for]

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Helene C. Stikkel // Wikicommons

1999: Kosovo Force

- Army strength: 477,788 people
- Navy strength: 372,507 people
- Marine Core strength: 172,635 people
- Air Force strength: 360,510 people
- Total strength: 1,383,440 people
- Percent of population enlisted: 0.50%

President Clinton called for 7,000 U.S. military troops to assist NATO’s “Kosovo Force” security team in Kosovo, where the Federal Republic of Yugoslavia—comprised of the republics of Montenegro and Serbia—was in conflict with the Kosovo Liberation Army. Later that year, the U.S Senate dismissed the ratification of the Comprehensive Test Ban Treaty. As part of the no-fly zone over Iraq, the U.S. took retaliative and preventive measures against the threats of Iraqi military forces.

[Pictured: A solider poses with Secretary of Defense William S. Cohen in Kosovo]

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Public Domain // Wikicommons

2000: USS Cole bombing

- Army strength: 483,115 people
- Navy strength: 371,543 people
- Marine Core strength: 172,955 people
- Air Force strength: 355,601 people
- Total strength: 1,383,214 people
- Percent of population enlisted: 0.49%

Two al-Qaeda suicide bombers attacked the USS Cole, killing 17 U.S. sailors and injuring 39. In response, President Clinton approved 45 U.S. naval personnel to contribute medical and security assistance. Navy combat ships were situated near Yemeni waters to provide additional support. One of the men who helped coordinate the attack was believed to be killed in 2019 in Yemen, according to a U.S. administration official.

[Pictured: USS Cole after the attack]

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Michael Foran // Wikimedia Commons

2001: Sept. 11 attacks

- Army strength: 482,655 people
- Navy strength: 377,312 people
- Marine Core strength: 176,720 people
- Air Force strength: 363,692 people
- Total strength: 1,400,379 people
- Percent of population enlisted: 0.49%

Nineteen militants on the morning of Sept. 11, 2001, orchestrated a coordinated attack against The World Trade Center in New York City and The Pentagon in Arlington, Va. by highjacking four planes and flying them into buildings. Nearly 3,000 people died in the attacks and more than 6,000 were injured—there were no survivors on any of the hijacked planes. Two planes struck the towers of The World Trade Center, one crashed into The Pentagon, and another crashed in a Pennsylvania field. The attacks launched the worldwide “War on Terror,” a global military campaign still in effect today. As part of this effort, President George W. Bush approved an executive order permitting military tribunals against any foreign residents thought to have ties to terrorist groups. U.S. forces invaded Afghanistan later that year, with the intent of defeating al-Qaeda.

[Pictured: The Twin Towers on September 11, 2001]

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Spc. David Marck Jr. // U.S. Army photo

2002: Operation Anaconda

- Army strength: 488,631 people
- Navy strength: 385,009 people
- Marine Core strength: 177,868 people
- Air Force strength: 369,112 people
- Total strength: 1,420,620 people
- Percent of population enlisted: 0.49%

The U.N. Security Council in January 2002 called for an arms embargo and the freezing of Osama bin Laden's assets. U.S. forces carried out Operation Anaconda from March 2 to 10 in Afghanistan, killing anywhere between 100 and 1,000 members of the Taliban and al-Qaeda. There were 80 casualties among U.S. forces, including 8 dead and 72 wounded.

That October, Congress passed the Iraq Resolution, which allowed the U.S. to take military action against Iraq. In November, President Bush passed the Homeland Security Act, which officially established the Department of Homeland Security.

[Pictured: Soldiers during Operation Anaconda]

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Capt. Patricia Lang // U.S. Air Force photo

2003: Shock and awe

- Army strength: 497,770 people
- Navy strength: 382,655 people
- Marine Core strength: 181,166 people
- Air Force strength: 375,859 people
- Total strength: 1,437,450 people
- Percent of population enlisted: 0.50%

The U.S. and U.K. invaded Iraq in late March of 2003, starting with a “ shock and awe” campaign designed to use dramatic force to cripple the enemy. That April, U.S. soldiers defeated the Iraqi Army and the Iraqi Republican Guard in the Battle of Baghdad. Later that year, President Bush confirmed that there was no evidence to substantiate Saddam Hussein's involvement in the Sept. 11 attacks.

[Pictured: A soldier assess the damage after targeting one of Saddam Hussein's presidential palaces as part of the "shock and awe" campaign]

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Sgt. Jeremiah Johnson, U.S. Army // Wikicommons

2004: No weapons of mass destruction

- Army strength: 498,428 people
- Navy strength: 372,525 people
- Marine Core strength: 177,021 people
- Air Force strength: 376,813 people
- Total strength: 1,424,787 people
- Percent of population enlisted: 0.49%

In February of 2004, the CIA announced there was no evidence of weapons of mass destruction in Iraq prior to the U.S. invasion. In October, video footage of Osama bin Laden aired on Arab state-sanctioned television, in which he threatened to terrorize the U.S. and mocked President Bush over the World Trade Center attacks. In December, as U.S. forces continued to occupy Iraq, revolutionaries attacked a U.S. outpost in Mosul, resulting in 22 fatalities. Two days later, U.S. soldiers killed the revolutionaries in Fallujah.

[Pictured: Soldiers standing gaurd in front of a building in Mosul, Iraq in 2004]

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Pool // Getty Images

2005: Rumsfeld announces troop reduction

- Army strength: 490,632 people
- Navy strength: 362,239 people
- Marine Core strength: 179,840 people
- Air Force strength: 353,696 people
- Total strength: 1,386,407 people
- Percent of population enlisted: 0.47%

Early in 2005, North Korea claimed possession of nuclear weapons as a precautionary measure against “hostile” U.S. forces. Worldwide, citizens continued protesting the Iraq War—including more than 150,000 people who took to the streets of Washington D.C. In December, Secretary of Defense Donald Rumsfeld announced the reduction of U.S. troops in Iraq.

[Pictured: U.S. Secretary of Defense Donald Rumsfeld (center) talks to soldiers after announcing a reduction in size of the U.S. forces in Iraq]

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James Bowman // DoD photo

2006: Saddam hanged

- Army strength: 507,131 people
- Navy strength: 349,534 people
- Marine Core strength: 180,252 people
- Air Force strength: 348,953 people
- Total strength: 1,385,870 people
- Percent of population enlisted: 0.46%

Thirteen years after its initial congressional approval, a United States Air Force Memorial depicting three spires “ Soaring to Glory” was dedicated Oct. 14, 2006. A month later, Defense Secretary Donald Rumsfeld announced his resignation. And on Dec. 30, Saddam Hussein was hanged in Baghdad following his conviction for crimes against humanity. Grainy scenes from his execution were captured and widely shared online, concerning U.S. and British governments in light of accusations of sectarian bias under Iraqi Prime Minister Nouri al-Maliki.

[Pictured: Secretary of Defense Donald H. Rumsfeld announces his resignation while President George W. Bush stands in the background]

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The U.S. Army // Flickr

2007: 21,500 more soldiers to Iraq

- Army strength: 522,190 people
- Navy strength: 336,659 people
- Marine Core strength: 186,425 people
- Air Force strength: 333,495 people
- Total strength: 1,378,769 people
- Percent of population enlisted: 0.46%

Early in 2007, U.S. Air Force units carried out airstrikes in Somalia in the wake of suspected terrorist activity. President Bush took measures to deploy 21,500 additional U.S. soldiers to Iraq. In a battle involving Iraqi revolutionaries and U.S.-supported Iraqi troops, 300 alleged insurgents were killed in Najaf, Iraq. In December, the National Intelligence Estimate conveyed its confidence that Iran's nuclear weapons facilities had been dormant since 2003.

[Pictured: Soldiers in Baghdad, Iraq on April 5, 2007]

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U.S. Navy Petty Officer 1st Class Chad J. McNeeley // Defense Dept. photo

2008: U.S. Navy takes out U.S. spy satellite

- Army strength: 544,150 people
- Navy strength: 331,132 people
- Marine Core strength: 198,415 people
- Air Force strength: 327,382 people
- Total strength: 1,401,079 people
- Percent of population enlisted: 0.46%

The U.S Navy wiped out an American spy satellite in February of 2008, causing countries around the world to accuse the U.S. of testing its ability to compromise satellites belonging to other countries. The wars in Iraq and Afghanistan continued to proliferate.

[Pictured: Following the succesful destruction of a spy satellite, Navy Capt. Randall M. Hendrickson sepaks to reporters]

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SAUL LOEB // Getty Images

2009: Orders to close Guantanamo Bay

- Army strength: 553,579 people
- Navy strength: 328,751 people
- Marine Core strength: 203,075 people
- Air Force strength: 333,408 people
- Total strength: 1,418,813 people
- Percent of population enlisted: 0.46%

Newly appointed President Barack Obama signed orders to shut down the Guantanamo Bay detention camp, and put a stop to the use of torture in interrogations. In April, Somali pirates hijacked the American freighter Maersk Alabama and kidnapped its captain. As the U.S. Navy engaged in a standoff, a sniper killed three pirates.

[Pictured: President Barack Obama signs an executive order closing Guantanamo Bay]

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Chuck Kennedy // Official White House Photo

2010: Don’t Ask Don’t Tell Repeal Act

- Army strength: 566,045 people
- Navy strength: 327,697 people
- Marine Core strength: 202,612 people
- Air Force strength: 334,198 people
- Total strength: 1,430,552 people
- Percent of population enlisted: 0.46%

In his first State of the Union address, President Obama discussed abolishing the military's “Don't Ask Don't Tell” policy on homosexuality. Instituted in 1994, the policy banned military personnel from victimizing or harassing closeted gay and bisexual members of the military, and banned openly gay or bisexual people from serving in the military. In December of that year, Obama passed the repeal on “Don't Ask Don't Tell” into law. The U.S. Navy revoked its ban on women serving in submarines. The last U.S. troops began leaving Iraq, and Obama announced that combat operations in Iraq would be discontinued.

[Pictured: President Barack Obama signs the Don't Ask, Don't Tell Repeal Act of 2010]

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Pete Souza // Wikicommons

2011: Osama bin Laden killed

- Army strength: 565,463 people
- Navy strength: 324,666 people
- Marine Core strength: 201,026 people
- Air Force strength: 333,162 people
- Total strength: 1,424,317 people
- Percent of population enlisted: 0.46%

In May of 2011, President Obama declared that U.S. military forces had killed al-Qaeda leader Osama bin Laden in Pakistan. In June, modified U.S. military strategy was adjusted to reflect that a cyberattack would be a legitimate reason to declare war. Shortly after, an FBI investigation revealed that Chinese hackers had tapped into American and Chinese Gmail accounts.

[Pictured: President Barack Obama shakes hands with Admiral Mike Mullen in the White House after the mission against Osama bin Laden]

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Erin A. Kirk-Cuomo // Wikicommons

2012: Benghazi attack

- Army strength: 550,063 people
- Navy strength: 318,818 people
- Marine Core strength: 198,820 people
- Air Force strength: 332,834 people
- Total strength: 1,400,535 people
- Percent of population enlisted: 0.45%

NATO leaders at the Chicago Summit talked about nuclear weapons, the Middle East, Russia, and Afghanistan, including supporting an exit strategy. On Sept. 11, members of Islamic militia group Ansar al-Sharia launched an attack on a U.S. diplomatic building in Benghazi, killing U.S. Ambassador J. Christopher Stevens and Foreign Service Officer Sean Smith. This prompted the U.S. to increase security measures on an international level and launched an

[Pictured: Sept. 14, 2012, Secretary of State Hillary Rodham Clinton speaks about the Benghazi attack]

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Erin A. Kirk-Cuomo // DOD photo

2013: Women can serve in combat

- Army strength: 532,043 people
- Navy strength: 324,308 people
- Marine Core strength: 195,848 people
- Air Force strength: 330,485 people
- Total strength: 1,382,684 people
- Percent of population enlisted: 0.44%

In January of 2013, Secretary of Defense Leon Panetta revoked the ban on women serving in combat missions. Shortly after, a crisis in North Korea began to take form: Threats of nuclear warfare were issued against South Korea and the U.S. In August, the Syrian government was accused of killing more than 1,000 people with chemical weapons.

[Pictured: Defense Secretary Leon E. Panetta signs a document dending the ban on women participating in combat missions]

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Marine Corps Sgt. Aaron Hostutler // DOD photo

2014: Slashes to military budget

- Army strength: 508,210 people
- Navy strength: 326,054 people
- Marine Core strength: 187,891 people
- Air Force strength: 316,332 people
- Total strength: 1,338,487 people
- Percent of population enlisted: 0.42%

The Obama administration suggested decreasing the military budget to $522 billion, and reducing the army to a size it had not been since before WWII. In June, Obama said that he would deploy up to 300 military advisers to Iraq to assist the Shiites when they were threatened by the Sunni militant group who would come to be known as the Islamic State group. In November, 1,500 troops were sent to Iraq to further combat the Islamic terrorist organization. And in December, the U.S. and U.K. officially removed their military forces from major combat operations in Afghanistan.

[Pictured: On February 24, 2014, Defense Secretary Chuck Hagel shares reccomendations for the 2015 fiscal year to reporters]

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Obama White House Photo

2015: Iran sanctions lifted

- Army strength: 491,365 people
- Navy strength: 327,801 people
- Marine Core strength: 183,417 people
- Air Force strength: 311,357 people
- Total strength: 1,313,940 people
- Percent of population enlisted: 0.41%

In July of 2015, the U.S. and Iran agreed to remove most of the United Nations Security Council's sanctions on Iran in exchange for imposing limits on Iran's nuclear programs for at least 10 years. Later that year, Defense Secretary Ashton Carter declared that women could serve in all combat roles in the U.S. military by April 1 of the following year.

[Pictured: President Barack Obama explains the details of the nuclear deal with Iran]

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U.S. Department of State // Flickr

2016: Nuclear Summit

- Army strength: 475,400 people
- Navy strength: 324,524 people
- Marine Core strength: 183,501 people
- Air Force strength: 317,883 people
- Total strength: 1,301,308 people
- Percent of population enlisted: 0.40%

In January of 2016, the U.S. government executed its promise to remove economic sanctions from Iran, in line with the agreement established the previous year. Sanctions related to violations of human rights, the use of missiles, and support of terrorism stayed in effect. The 2016 Nuclear Summit took place in Washington D.C., during which a revised nuclear security agreement was drawn up. Since 2014, 10 countries have disposed of roughly 450 kilograms of highly enriched uranium. In July of 2016, the U.S. military removed its restriction on transgender people serving in the military.

[Pictured: U.S. Secretary of State John Kerry and European Union High Representative for Foreign Affairs Federica Mogherini during the Nuclear Security Summit ]

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Ted Eytan // Wikicommons

2017: Transgender ban in the military

- Army strength: 476,245 people
- Navy strength: 323,933 people
- Marine Core strength: 184,401 people
- Air Force strength: 322,787 people
- Total strength: 1,307,366 people
- Percent of population enlisted: 0.40%

In J anuary of 2017, President Donald Trump made the executive decision to deny refugees of the Syrian Civil War entry into the U.S., as well as citizens of Iran, Iraq, and several other Middle Eastern countries. North Korea launched four ballistic missiles toward the Sea of Japan.

President Trump also vowed to reinstate a transgender ban in the military that Obama had reversed. The regulation was enacted in March 2017. In October, Trump outwardly criticized Iran, and suggested an end to the previous Iran Nuclear Deal unless serious revisions were made. A report released in September 2017 from the U.S. Department of Veterans’ Affairs found that on average, 20 veterans a day die from suicide and that veterans’ risk of suicide is 22% higher than a non-veteran adult.

[Pictured: People protest to stop the Transgender Military Ban]

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NASA/Bill Ingalls // Wikicommons

2018: Space Force

- Army strength: 416,667 people
- Navy strength: 285,141 people
- Marine Core strength: 153,107 people
- Air Force strength: 266,167 people
- Total strength: 1,121,082 people
- Percent of population enlisted: 0.34%

The U.S., along with the U.K. and France, launched more than 100 missiles against chemical weapons threats in Syria early on the morning of April 14, 2018. The three targets, reported by the Pentagon, were a chemical weapons storage facility, a scientific research center, and a third command post and storage site. The Western powers said these strikes were in retaliation of the Douma, Syria, chemical attack on April 7, which killed dozens of civilians.

On June 18 during a National Space Council meeting, President Trump announced he would direct the Department of Defense and Pentagon to create a sixth branch of the U.S. military: the Space Force to assert “American dominance in space.”

[Pictured: President Donald Trump holds up a signed Space Policy Directive]

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VYACHESLAV OSELEDKO // Getty Images

2019: Iran reveals new missile defense system

- Army strength: 416,876 people
- Navy strength: 290,254 people
- Marine Core strength: 154,909 people
- Air Force strength: 270,328 people
- Total strength: 1,132,367 people
- Percent of population enlisted: 0.34%

Calling American talks “useless,” Iran in August 2019 unveiled a new, long-range missile system that can recognize targets more than 190 miles away. The mobile Bavar-373 system missile system is similar to Russia’s S-300 missile system and follows Iran’s June takedown of a U.S. military surveillance drone.

[Pictured: Iran President Hassan Rouhani who said in August that talks with America are "useless" ]

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