Robert W. Aschenbrener was born on November 22, 1920 in Fifield, Wisconsin. From 1939 to 1940, Aschenbrener attended Loras College in Iowa before enlisting into the United States Army Air Forces' Aviation Cadet Program on January 12, 1942. He was commissioned as a 2nd lieutenant and awarded with his pilot's wings at Moore Field, Texas on September 6. From there, he began advanced training with the Curtiss P-40 Warhawk and subsequently was assigned to the 8th Fighter Squadron stationed in New Guinea in May of 1943.