Opération Castor was a French airborne operation in the First Indochina War. The operation established a fortified airhead in Điện Biên Province, in the north-west corner of Vietnam. Commanded by Brigadier General Jean Gilles, Castor was the largest airborne operation since World War II. The Operation began at 10:35 on 20 November 1953, with reinforcements dropped over the following two days.