First Lieutenant Simmon was a member of the Air/Navy Gunfire Liaison Company, 1st Signal Battalion, 1st Marine Division. On 3 February 1951, he was the pilot of a F4U-4 Corsair fighter from Marine Fighter Squadron 312, aboard the carrier USS Bataan (CVL-29) on a combat mission near North Pyongchong. His aircraft crashed into a ridge line.
Simmon was awarded the Purple Heart, the Combat Action Ribbon, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal and the Republic of Korea War Service Medal.