Private First Class Greenwood was a member of the 17th Infantry Regiment, 7th Infantry Division. He was seriously wounded by the enemy in North Korea on 28 May 1951 and returned to duty on 9 June 1951. He was Killed in Action while fighting the enemy in North Korea on 1 September 1951.

Greenwood was awarded the Purple Heart with Oak Leaf Cluster, the Combat Infantryman's 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.