David Sarnoff, the American businessman and radio and television pioneer, served in the U.S. Army during World War I but did not serve in the military during World War II.
However, Sarnoff did play an important role in the war effort as the chairman of the Radio Corporation of America (RCA), which was a major supplier of communications equipment to the U.S. military during the war. He also served as a member of the National Defense Research Committee and was involved in the development of radar and other military technologies.
To answer your question more directly, Sarnoff did not hold an Army rank during or after World War II.