Harry Flater served as a member of the Office of Strategic Services (OSS) Operational Group Pat, one of the thirteen American parachutists of Operation Percy Pink under the leadership of 1st Lt. Thomas Allen Legare.

On August 12, 1944, he parachuted into the drop zone known as La Roche near Cadouin, France, along with twelve fellow operatives and interpreter Leon Robert, delivered by three B-24 “Liberator” aircraft laden with 51 containers of arms and supplies. From their base at the Château de Bétou, Flater helped arm and train the French Maquis, collaborate with British SOE agents, and carry out sabotage operations—disrupting German fuel depots and transport routes in the Dordogne. After nearly a month behind enemy lines, he safely returned to the United Kingdom on September 10, 1944.

Currently, we don't have details regarding his postwar life, as well as the circumstances of his death or place of burial.