With the outbreak of the Korean War, Major Sawyer was given command of 2nd Battalion, 7th Marines, 1st Marine Division. He took part in the landing at Inchon and the battle of Seoul in September 1950. On the night of November 3, 1950, during the advance into North Korea from Wonsan, Sawyer's battalion was fiercely assaulted, but he managed to close numerous gaps created in the line and led his Marines to victory. One week later, subzero temperatures arrived in the Chosin Reservoir area, and the Chinese military followed by the end of the month, beginning the battle of Chosin Reservoir. The Marines began retreating back to Wonsan.