In the United States, military conscription, commonly known as the draft, has been employed by the U.S. federal government in six conflicts: the American Revolutionary War, the America Civil War, World War I, World War II, the Korean War, and the Vietnam War. The fourth incarnation of the draft came into being in 1940, through the Selective Training and Service Act; this was the country's first peacetime draft.

From 1940 until 1973, during both peacetime and periods of conflict, men were drafted to fill vacancies in the U.S. Armed Forces that could not be filled through voluntary means. Active conscription in the United States ended in January 1973, and the U.S. Armed Forces moved to an all-volunteer military except for draftees called up through the end of 1972.

The registration of men between the ages of 21 and 27 began one month later, as Secretary of War, Henry L. Stimson—a key player in moving the administration of Franklin D. Roosevelt away from a foreign policy of neutrality—began drawing draft numbers out of a big glass bowl. The draft numbers were handed to the President, who then read them aloud for public announcement.

After the United States entered World War II, it expanded the draft ages to include men 18 to 37. 18 year-olds were required to register for the draft by their 18th birthday.

Between 1948 and 1973, men were drafted into the Armed Forces in both peacetime and conflict periods. Today, the Selective Service System remains in "Standby" mode should Congress deem it necessary to resume military conscription.

Conscientious Objectors
“Conscientious objector” status was granted to those who could demonstrate “sincerity of belief in religious teachings combined with a profound moral aversion to war.” Conscientious Objectors are also known as "Draft-Dodgers." Some men evaded the draft by failing to register with the Selective Service System or by fleeing the country. According to Canadian immigration statistics, as many as 30,000 draft dodgers may have left the US for Canada during the Vietnam War.

Draft evasion carried steep fines and possibility of jail time. Nearly, 210,000 men were charged with draft evasion, including boxer Muhammad Ali, whose conviction was overturnd by the U.S. Supreme Court.

The large cohort of Baby Boomers eligible for military service during the Vietnam War allowed a steep increase in the number of exemptions and deferments, especially for college students. Besides being able to avoid the draft, college graduates who volunteered for military service (primarily as commissioned officers) had a much better chance of securing a preferential posting compared to less-educated inductees. Some had health issues, religious beliefs, stated their own personal belief that they could not shoot and kill people. Contrary to popular belief, the large majority of American soldiers who participated in the war, and who were killed in combat, were in fact volunteers and not draftees.

The marriage deferment ended suddenly on August 26, 1965. Around 3:10 pm, President Johnson signed an order allowing the draft of men who married after midnight that day, then around 5 pm, he announced the change for the first time. This caused a last-minute rush to the altar by thousands of American couples.

Some conscientious objectors objected to the war based on the theory of "Just War" and ended up in jail. Some received "Suspended Sentences." During the Vietnam War Era, some of the "Draft Dodgers" rioted and burned their draft cards.

On February 2, 1972, a drawing was held to determine draft priority numbers for men born in 1953, but in January 1973, Secretary of Defense Melvin Laird announced that no further draft orders would be issued. In March 1973, 1974, and 1975, the Selective Service assigned draft priority numbers for all men born in 1954, 1955, and 1956 in case the draft was extended, but it never was.

Command Sergeant Major Jeff Mellinger, believed to be the last drafted enlisted ranked soldier still on active duty, retired in 2011. Chief Warrant Officer 5 Ralph E. Rigby, the last Vietnam War-era drafted soldier of Warrant Officer rank, retired from the army on November 10, 2014, after a 42-year career.

December 28, 1972, had been scheduled to be the last day that draftees would be inducted that year. However, President Nixon declared that day a national day of mourning due to the death of former President Truman, and Federal offices were closed. Men scheduled to report that day were never inducted since the draft was not resumed in 1973.

In 1977. President Jimmy Carter pardoned all Vietnam War draft dodgers.

(Information obtained from Wikipedia. Background of Selective Service System.)