First Lieutenant Milligan was the navigator of a B-26B Invader bomber with the 8th Bomber Squadron, 3rd Bomber Group, based at Iwakuni Air Base, Japan. On October 19, 1950, while participating in night intruder mission over Sianju, Korea in bad weather, contact with the Aircraft was lost. He was listed as Missing in Action and was presumed dead on December 31, 1953. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.