Wilson went on to lead what was at the time the largest war-mobilization effort in the country’s history. At first, Wilson asked only for <em>Volunteer Soldiers</em>, but soon realized voluntary enlistment would not raise a sufficient number of troops and signed <em>The Selective Service Act in May 1917. </em>The Selective Service Act required men between 21 and 35 years of age to register for the draft, increasing the size of the army from 200,000 troops to 4 million by the end of the war. One of the infantrymen who volunteered for active duty was future President Harry S. Truman.
