Second Lieutenant Ballmer was a pilot of a F4U-4 Corsair fighter with the Marine Fighter Squadron 212, Marine Air Group 33, 1st Marine Air Wing. On 16 April 1951, while on a combat mission of striking an enemy supply dump in a flight of two, his aircraft crashed killing him. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Ballmer 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.