American Expeditionary Forces Distinctive Cloth Insignia Chart.
For reference, on 6 April 1917, when the U.S. declared war against Imperial Germany, the nation had a standing army of 127,500 officers and men while the entire National Guard had another 181,620 members. The concept of full divisional-sized operations was almost alien, an abstract theory.
By Armistice Day, one cavalry division and a staggering 63 infantry divisions were planned, although many of those never took the field. By the end of the war, over four million men had served in the United States Army, with an additional 800,000 in other military service branches. While 24,234,021 men registered for the draft, a full third of those that served in the ranks were volunteers. Some 745,845 left in the American Expeditionary Forces.