Corporal Winthrop was a medic with the Medical Company, 35th Infantry Regiment, 25th Infantry Division. He was Killed in Action while tending his wounded comrades in South Korea on 17 August 1950.

Winthrop was awarded the Purple Heart, the Combat Medical 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.