 During World War II, General Hart was awarded the Navy Cross while commanding the 24th Marines in the assault and capture of Roi-Namur Island, Kwajalein Atoll, and was awarded the Legion of Merit while leading the regiment in the battles for Saipan and Tinian in the Marianas Islands.As assistant division commander, Fourth Marine Division, during the assault at Iwo Jima, he was awarded the Bronze Star.His citation for the Navy Cross reads in part, "Landing when the assault troops had advanced only one hundred yards from the beach, Colonel Hart fearlessly led his combat team against heavy enemy resistance in a crushing attack toward its first objective."