Final answer:
Initially, the US Army had only 122,000 enlisted men and was supported by 180,000 National Guard units' members. During the war, 1.5 million men volunteered for service, contributing to a larger force that included over 500,000 additional volunteers for the navy or marines. The introduction of the Selective Service Act of 1940 signified the start of the peacetime draft, which was critical for rapid military expansion.
Step-by-step explanation:
Volunteers in the US Army Before the Draft
Before the draft was enforced, the United States Army was relatively small, canvassing only 122,000 enlisted men in the regular army and potentially boosted by another 180,000 men from various state-run National Guard units. However, these numbers were insufficient to meet the demands of emerging global conflicts.
As the nation edged closer to participation in war, the number of volunteers did not grow substantially despite legislative acts such as the National Defense Act, which allowed for an expansion of the army. Faced with the challenge of rapidly assembling a competent military force, the US initially relied on voluntary enlistment and saw a significant number of African American volunteers, despite a ceiling on how many would be accepted.
The Selective Service Act of 1940 marked the beginning of the peacetime draft in American history, and by the war's end, an impressive twenty-two million men had registered for the draft. Out of these, five million were drafted, and another 1.5 million took the initiative to volunteer. Additionally, over 500,000 signed up for the navy or marines. The result was a considerable force wherein two million men participated in overseas combat operations, and this included twenty thousand women volunteers who served in various roles such as nurses and in clerical positions.