Osprey's study of the African Americans' involvement in World War II (1939-1945). Despite the contribution of black units to the American Expeditionary Force in World War I (1914-1918), and the commissioning of hundreds of black officers to lead them, the small interwar US Army continued to regard them as unsuited to both leadership roles and handling modern technology. Although African Americans had to strive against prejudice for every chance to show what they could achieve, in fact the wartime US Army conceded opportunities for leadership unparaleled in American civil society at that date. In World War II tens of thousands served in segregated units. While the majority were denied the opportunity of combat, a minority of all-black, black-officered units proved their worth in all theaters and a number of roles: black officer fighter pilots (the "Tuskegee Airmen") blazed the trail, followed by several tank and tank-destroyer battalions and a few field artillery units; and more than 20,000 black infantrymen served under both white and black officers. The Army also created the first fully integrated units, whose success prompted President Truman to order the complete integration of the military in 1948. The US Navy and Marines were slower to allow blacks to serve in combat roles and to commission black officers, but by 1945 two complete ships' companies were composed of African-Americans (though with white officers).