Corporal Westerman was a member of the Support Company, Supply Battalion, 1st Combat Service Group, Combat Service Command, Fleet Marine Force, Pacific. He was listed as Missing in Action while fighting the enemy in Korea on 21 September 1952. He was presumed dead on 8 January 1954. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Westerman was awarded the Purple Heart, the Combat Action Ribbon, 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.