Fox enlisted in the United States Marine Corps Reserve on 4 May 1939. He was commissioned as a second lieutenant on 29 November 1940 and promoted to first lieutenant on 11 April 1942. In the initial assault of the Guadalcanal campaign, Fox was with the 1st Marine Raider Battalion during the seizure of Tulagi on the night of 7 August 1942. He ignored mortal wounds to deploy his men to fill a gap in the American lines, thus repulsing a Japanese attack with heavy losses. Fox was posthumously awarded the Navy Cross. The destroyer escort was named for him, but its construction was cancelled in 1944.