Following the fall of France, Fielding joined the Army, and was commissioned into the Cyprus Regiment as a second lieutenant on 1 September 1940. After the fall of Crete in May 1941, he joined the Special Operations Executive, and was eventually landed in Crete with a supply of weapons and explosives by the submarine , under Commander Anthony Miers. Fielding teamed up with Patrick Leigh Fermor, and built an intelligence gathering network which provided detailed information on the movement of Axis troops, shipping, and air transport.