The United States formally entered the First World War on April 2, 1917 and six weeks later on May 18, 1917, the U.S. Congress passed the Selective Service Act.
In his war message to Congress, President Woodrow Wilson pledged all the nation’s material resources to help the allies (France, Britain, Russia and Italy) defeat the Central Powers. The Allies needed fresh troops to relieve their exhausted men but when the United States entered the war, Wilson had no means to provide what was needed.
During 1916, Wilson made effort in war preparedness but at the time of Congress’s war declaration, there were only 100,000 troops and they were not trained or equipped for the war in Europe. Wilson pushed congress for military conscription which they passed on May 18, 1917. The Act called for all men in the U.S. between the ages of 21 and 30 to register for the draft. Within a few months, 10 million men across the country had registered.
The first troops of the American Expeditionary Force (AEF) began arriving in Europe in June 1917. The rest of the newly conscripted men still needed to be mobilized, transported and trained so the AEF did not begin to play a substantial role until the summer of 1918. The U.S. role in the interim was in the form of economic assistance to the Allies. World War I ended in November 1918. About 24 million men had registered for the Selective Service act. Almost 4.8 million American served in the war and 2.8 million of them had been drafted.