During the Korean War, First Lieutenant Mitchell was a rifle company platoon commander in Company A, 1st Battalion, 7th Marine Regiment, 1st Marine Division; the 7th Marines were activated on August 17, 1950 at Camp Pendleton. The 7th Marines and Mitchell, left Camp Pendleton and sailed for Japan on September 1. On September 21, the 7th Marines made an amphibious landing at Inchon, South Korea. His regiment including the 1st Battalion, rejoined the 1st Marine Division which had made an assault landing at Inchon on September 15, and participated with the division in the battle of Seoul against North Korean forces. On September 26, Mitchell personally led his platoon up a well defended hill and overtook the enemy. He was awarded the Bronze Star Medal with Combat "V" "for heroic achievement in connections with operations against the enemy while serving with Company A... during the period 24 September 1950 to 4 October 1950". The 7th Marines landed ashore next at Wonsan on October 27.