Following the Saipan battle, 4th Marine Division got a new commander, Major General Clifton B. Cates. Cumming remained in the capacity of assistant division commander under him and led his 4th Marine Division during the amphibious landing on Tinian on July 24, 1944. Shortly after the landing, Japanese units commenced the large night counterattack with tanks and support infantry using Banzai charges. An attack was successfully repelled and 1241 enemy bodies were around the defense perimeter. The 4th Division subsequently captured the enemy airfield in construction and the town of San Jose. On August 1, an island was declared secured after only 9 days of fighting. For his service in Marianas, Cumming received the Bronze Star Medal with Combat "V".