First Lieutenant Caldwell was a member of the 2nd Engineer Combat Battalion, 2nd Infantry Division. He was seriously wounded by the enemy in South Korea on 27 September 1950 and returned to duty on 28 October 1950. He was taken Prisoner of War while fighting the enemy near Kunu-ri, North Korea on 30 November 1950 and died while a prisoner on 17 May 1951.

Caldwell was awarded the Purple Heart, the Prisoner of War Medal, 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.