It varied widely from unit to until based in large part on what region of the country they were stationed. During WWII the 92nd Infantry Div was a mostly black combat unit in Italy commanded by a notorious racist, and arguably one of the most incompetent generals of WWII, Ned Almond. Under his leadership black officers and soldiers in general were treated very poorly, and for the most part this was pretty normal during WWII and Korea. Jackie Robinson was a commissioned officer in the Army during WWII and his experience was pretty typical of many pre-integration officers. Even post-integration in Korea it was an unofficial rule that when possible black officers would not command white troops. Even into the Vietnam era which is 20 years after the official integration of the military there are many instances of white soldiers refusing orders from black officers and NCOs. What really turned things around was the introduction of the all volunteer Army in the 1970s. You might want to also read up on the 555th Parachute Infantry, an all black paratrooper outfit. Courage Has No Color by Tanya Stone is a solid read.