Corporal Neisz was a medic with the Medical Company, 31st Infantry Regiment, 7th Infantry Division. He was listed as Missing in Action while tending his wounded comrades in North Korea on 1 December 1950. He was presumed dead on 31 December 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

Neisz was awarded the Purple Heart, the Combat Medical Badge, 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.