First Lieutenant Delplain was a member of Company C, 1st Battalion, 23rd Infantry Regiment, 2nd Infantry Division. He was Killed in Action while fighting the enemy near Kujang on the Clangchon River in North Korea on 28 November 1950. His remains were not recovered. His name is inscribed on the Courts of the Missing at the Honolulu Memorial.

For his leadership and valor, First Lieutenant Delplain was awarded the Silver Star Medal, the Bronze Star Medal, the Purple Heart with Oak Leaf Cluster, the Combat Infantryman 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.