Congress passed the Selective Service Act in May 1917—one month after the United States declared war against Germany. The act established the first nationwide draft. It initially required all men between the ages of 21 and 30 to register with local draft boards. The government eventually expanded the draft to include men between the ages of 18 and 45. The draft boards issued a number to the men as they registered. When the military needed more troops, the government would hold a lottery. The men with the number drawn had to report for military service. Nearly 24 million men registered for the draft during the war. Of those, over 2.8 million men were drafted for service. Some 2 million served overseas. The government used this system again during World War II, the Korean War, and the Vietnam War.
