<P> By the guidelines set down by the Selective Service Act , all males aged 21 to 30 were required to register for military service . At the request of the War Department , Congress amended the law in August 1918 to expand the age range to include all men 18 to 45 , and to bar further volunteering . By the end of World War I , some 2 million men volunteered for various branches of the armed services , and some 2.8 million had been drafted . This meant that more than half of the almost 4.8 million Americans who served in the armed forces were drafted . Due to the effort to incite a patriotic attitude , the World War I draft had a high success rate , with fewer than 350,000 men '' dodging '' the draft . </P>
whom did the selective service act of 1917 authorize the armed forces to conscript
all males aged 21 to 30 were required to register for military service