He was became commander of V Corps on 17 July, 1943. This was the largest unit of troops in the European Theater of Operations. He played a major part in the planning of the invasion of continental Europe. He was the first corps commander ashore on D-Day assault on Normandy on June 6, 1944. The V Corps was comprised of two infantry divisions: the U.S. 29th Infantry Division and the U.S. 1st Infantry Division. His tenure as commander of V Corps was from 17 July 1943 to 17 September 1944 and again 5 October 1944 to 14 January 1945. General Gerow kept close to his advancing troops in V Corps. He was the first American officer of the rank of Major General to enter Paris after it's liberation by the 2nd French Armored and U.S. 4th Infantry. For his part in this campaign he was awarded the Silver Star.

Then Captain J. Milnor Roberts served as Aide de Camp to Major General Gerow.