First Lieutenant Mercer was a member of Battery B, 555th Field Artillery Battalion, 5th Infantry Regimental Combat Team. He was Killed in Action while fighting the enemy near Chindong-ni, South Korea, on 8 August 1950.

Mercer was awarded the Purple Heart, the Korean Service Medal, the United Nations Service Medal, the National Defense Service Medal, the Korean Presidential Unit Citation and the Republic of Korea War Service Medal.