The difficulty in staffing was because over the course of the war the army expanded from under 200k soldiers to over 8 million, and the navy expanded from under

The difficulty in staffing was because over the course of the war the army expanded from under 200k soldiers to over 8 million, and the navy expanded from under 400k to over 3.4 million. That's almost 11 million people, which was around 12% of the civilian workforce, diverted to the military.