While the Royal Navy was experimenting with aircraft carrying submarines, the French Navy continued to pursue the unconventional submarine cruiser concept. The pinnacle of their (and all other navies’) experimentation was the submarine Surcouf which was commissioned in 1936. Surcouf displaced nearly 4,400 tons and was outfitted with dual 8-in. guns, 10 torpedo tubes, nearly half a dozen anti-aircraft and machine guns and a spotting aircraft in a stern hangar. Never before nor since have such large guns been mounted on a submarine. Named after a 19th century French privateer captain, the Surcouf was intended to be deployed as a submersible raider with the capability of shelling shore targets, merchant ships and unsuspecting surface warships and then sneaking away while submerged.
During World War II, the Surcouf had a rather lackluster reputation in the hands of the French Navy and Free French Navy. Barely escaping capture when the Nazi blitzkrieg overran France, the Surcouf fled to France where the Royal Navy later boarded her at gunpoint during Operation Catapult and the resulting confusion ended in the deaths of several sailors. The boat was then turned over to the Free French Navy and was used to assist in a coup launched on December 25, 1941 against the Vichy French administrator of Saint Pierre and Miquelon – a French colony off the coast of Canada.
Following several months of inconsequential service in which the sub constantly required maintenance, the decision was made by the Free French high command to dispatch Surcouf to Tahiti via the Panama Canal. After a temporary stop at Bermuda on February 7, 1942 the Surcouf sailed for the Canal Zone. The sub was never seen again and numerous theories have been proposed as to her fate. The two most widely accepted theories are that the sub collided with the American freighter Thompson Lykes on the night of February 18th or was sunk by American aircraft on February 19th.
The sub has never been located and there are rumors that the sub was carrying a portion of France’s gold reserves, however, this is most likely wild conjecture for several reasons. First, the Surcouf was operating primarily in the Caribbean and North Atlantic in her final months and thus would have had no access to the gold reserves. Second, and more importantly, the sub was experiencing significant mechanical difficulties and it is highly unlikely that gold reserves would have been entrusted to an unreliable vessel. Finally, the Surcouf had been ordered to Tahiti which is an unlikely destination (unless for transshipment) for any gold reserves.