Who was the Chief of Naval Operations during World War 2?

There were 2 CNO's during the period between 1939 and 1945 covering WWII:

Admiral Harold R. Stark - August 1, 1939 - March 2, 1942

Fleet Admiral Ernest J. King - March 2, 1942 - December 15, 1945

Stark relieved Admiral William Leahy - King was relieved by former CINCPAC Chester W. Nimitz.