In January 1944, he was assigned to the 4th Marine Division at Marine Corps Base Camp Pendleton, California where he was attached to the 2nd Battalion, 24th Marine Regiment of the division as a Fleet Marine Force hospital corpsman.
In 1948, Pierce was informed that the Navy Cross he received for extraordinary heroism and the Silver Star Medal for gallantry in action on Iwo Jima, were both being upgraded to the Medal of Honor.