William Dieter was born on October 5, 1912, in Vail, Iowa. He enlisted in the U.S. Army on October 29, 1936, and served in the Field Artillery until transferring to the U.S. Army Air Corps on December 12, 1940. Sgt Dieter was trained as a bombardier, and served as a B-18 Bolo and B-25 Mitchell bombardier with the 95th Bomb Squadron of the 17th Bomb Group at McChord Field, Washington, and then at Pendleton Field, Oregon, until he was selected for the Doolittle Mission in February 1942. Sgt Dieter was the bombardier on the sixth B-25 to take off from the aircraft carrier USS Hornet (CV-8) on April 18, 1942, and after bombing targets in Tokyo, his crew flew to China and ditched the plane off the coast. He drowned in the aircraft before he could get out. Sgt Dieter's remains were originally interred at Shatow, China, but they were later located and returned to the United States and he was reinterred at the Golden Gate National Cemetery in San Bruno, California, on January 10, 1949.

His Distinguished Flying Cross Citation reads:

For extraordinary achievement while participating in a highly destructive raid on the Japanese mainland on April 18, 1942. Sergeant Dieter volunteered for this mission knowing full well that the chances of survival were extremely remote, and executed his part in it with great skill and daring. This achievement reflects high credit on Sergeant Dieter and the military service.