Private First Class Hartmann was a member of Company E, 2nd Battalion, 8th Cavalry Regiment, 1st Cavalry Division. He was seriously wounded by the enemy in South Korea on September 4, 1950 and returned to duty on October 3, 1950. He was taken Prisoner of War while fighting the enemy near Unsan, North Korea on November 2, 1950 and died in a North Korean prison camp on March 31, 1951. His remains were not recovered. 

Through the work of the Defense POW/MIA Accounting Agency, the remains of Private First Class Harry J. Hartmann, Jr. were accounted for in 2023. His name is permanently inscribed on the “Courts of the Missing” at the Honolulu Memorial.