For conspicuous heroism and intrepidity above and beyond the call of duty during the Marine Raider Expedition against the Japanese-held island of Makin on 17-18 August 1942. Leading the advance element of the assault echelon, Sgt. Thomason disposed his men with keen judgment and discrimination and, by his exemplary leadership and great personal valor, exhorted them to like fearless efforts. On one occasion, he dauntlessly walked up to a house which concealed an enemy Japanese sniper, forced in the door, and shot the man before he could resist. Later in the action, while leading an assault on an enemy position, he gallantly gave his life in the service of his country. His courage and loyal devotion to duty in the face of grave peril were in keeping with the finest traditions of the U.S. Naval Service.