The conscription of American citizens into military service, commonly known as the Draft, has been used in six major wars: the American Revolution, the Civil War, World War I, World War II, the Korean War, and Vietnam. The first peacetime use of the draft was implemented in September 1940 as the United States prepared for possible entry into World War II. The Selective Training and Service Act of 1940 “required all men between the ages of 21 and 45 to register for the draft. Those who were selected from the draft lottery were required to serve at least one year in the armed forces. Once the U.S. entered WWII, draft terms extended through the duration of the fighting. By the end of the war in 1945, 50 million men between eighteen and forty-five had registered for the draft and 10 million had been inducted in the military.” The Draft ended in 1973 after the United States military became an all-volunteer military force. The Selective Service System still exists today mainly as a contingency plan; men between the ages 18 through 25 must register so that the Draft can resume if needed. The mission of the Selective Service System is “to register men and maintain a system that, when authorized by the President and Congress, rapidly provides personnel in a fair and equitable manner while managing an alternative service program for conscientious objectors.”
Perri, Timothy J. “The Evolution of Military Conscription in the United States,” Independent Review 17, no. 3 (2013): 429–439.