During World War I, 4.7 million Americans served in the military, among them Louis Santop Loftin, Ella Jane Osborn, and James Reese Europe. Louis Santop Loftin served in the US Navy, leaving behind a successful career in Negro Leagues baseball but returning to it after the war. Ella Jane Osborn was a nurse with the American Expeditionary Forces in France, serving just a few miles from the western front. Bandleader James Reese Europe was a lieutenant in the 369th Regiment, known as the Harlem Hellfighters.
Image Source: Ernest Dudley Chase, Service Stamps from World War I, 1917, Gilder Lehrman Institute, GLC07810.106