Nimitz was a graduate of the US Naval Academy, class of 1905.  Roosevelt had the opportunity to get to know Nimitz when Nimitz served as Chief of the Bureau of Navigation.  In December, after the attack on Pearl Harbor, he was appointed commander of the US Pacific Fleet.  Nimitz was a very effective commander, and led the US to victory in the Pacific. Nimitz was the one to receive the Japanese surrender at the end of the war.