Following the attack on Pearl Harbor, Hamlett was recruited to be corps artillery executive for II Corps. In 1942 he landed with the 1st Infantry Division on Arzew Beach near Oran, Morocco during the Allied invasion of North Africa. Drawing on his experience as an instructor at Fort Sill, he helped reorganize the previously ineffective corps artillery, helping mold it into a decisive arm. It was particularly noted for its ability to mass concentrated fire at the Battle of El Guettar.