 He was appointed chief of staff of the division in September 1942, at Guadalcanal, and in July 1943, he became chief of staff of the 1st Marine Amphibious Corps, where he was awarded the Legion of Merit with Combat "V" in the Treasury-Bougainville operation.After participating in the Empress Augusta Bay operation at Bougainville, he returned to Marine Corps Headquarters in Washington, D.C., where he was made director of Plans and Policies in January 1944 and awarded a second Legion of Merit for outstanding service from January 1944 to November 1946.In July 1947, Thomas was named Commanding General of Fleet Marine Force, Western Pacific.