The Surcouf was once the largest submarine in the world, until Japan took the record in 1944.

When one thinks of submarine warfare powers during World War II, chances are America’s “Silent Service” and Nazi Germany’s Unterseeboote (U-boats) are the first to come to mind, and perhaps the Imperial Japanese Navy’s (IJN) I-boats for good measure. The submarines of Great Britain’s Royal Navy, the Soviet Navy, and even the Royal Netherlands Navy made their impacts on the war effort as well.

That said, one major participant in WWII that’s almost an afterthought when it comes to submarine technology is France. Which is ironic, as, out of all the Allied nations, it was actually France that built the biggest sub of the bunch. Say “Bonsoir” to the French cruiser submarine Surcouf.

Surcouf Initial History and Specifications

As noted by the Dark Seas MSN channel in the text caption to their video titled “Massive French Battle Sub – The Surcouf”:

“The French submarine Surcouf was the largest and most powerful Allied submarine of its time, designed as an experimental cruiser with formidable firepower. Equipped with a floatplane, two 8-inch guns, anti-aircraft weapons, and heavy torpedoes, she was a true colossus of the sea. In early 1942, after being sent to Bermuda, Surcouf mysteriously vanished without a trace, and neither the Kriegsmarine nor the Japanese Navy claimed responsibility. Her disappearance remains one of World War II’s greatest naval mysteries, sparking countless theories about what really happened to the most potent Allied submarine.”

Built by Cherbourg Arsenal and named for Robert Surcouf (a French privateer who operated during the French Revolutionary and Napoleonic Wars), the Surcouf (Pennant No. NN-3, Designation No. 17P) was laid down on July 1, 1927, launched on November 18, 1929, and commissioned on April 16, 1934.

Tech specs and vital stats of the Surcouf were as follows:

• Hull Length: 361 feet (110 meters)
• Displacement: 3,304 tons surfaced; 4,373 tons submerged
• Beam Width: 29 feet 6 inches (9 meters)
• Draft: 23 ft 9 inches (7.25 meters)
• Propulsion: Two 3800-hp Sulzer diesel engines (for surface ops) and two electric motors (for submerged ops)
• Maximum Speed: 18 knots surfaced; 8.5 knots submerged
• Crew Complement: 118 (eight commissioned officers plus 110 enlisted sailors)
• Armament:
  • Two 8-inch (203 mm) guns mounted in a twin Model 1924 turret
  • Four 22-inch (550 mm) torpedo tubes in the bow; two 22-inch tubes and four 1-inch (400 mm) tubes in the aft superstructure (cleverly designed to pivot so the entire boat did not have to align with the target. 
  • Two 1.5-inch (37 mm) anti-aircraft guns
  • Four .52 caliber (13.2 mm) Hotchkiss anti-aircraft machine guns

This gargantuan submersible even had a watertight hangar to accommodate a Besson MB.411 “Petrel” seaplane!

For quite a while, the Surcouf held the record of being the largest submarine in the world, until she was superseded by the IJN Sen Toku/I-400-class in 1944. Surcouf’s label of “cruiser submarine” was apropos in more ways than one, as her 8-inch guns matched those of the heavy cruiser surface warships of the era.

Operational History and an Unsolved Mystery

Als, the mighty guns of Surcouf never enjoyed the satisfaction of being fired in anger. As noted by Bipin Dimri in a May 2022 article for Historic Mysteries:

“Surcouf’s wartime activities were almost over before they began. In 1940, Surcouf was being refitted in Brest and was barely seaworthy when the Germans invaded France. In a desperate race to escape German capture she headed to sea with only a single engine and extremely limited rudder control, managing to make it to Plymouth in the United Kingdom, and safety … The British, refusing to hand over Surcouf when the French surrendered, instead gave her to the Free French resistance. She would operate on the Allied side, largely in US and Canadian waters in the Atlantic, until a fateful night in 1942.”

That “fateful night in 1942” took place on February 18-19 of that year, when the submarine disappeared without a trace whilst traveling toward the Panama Canal, and beyond that, Tahiti. An official American report posited that the sub’s disappearance was due to an accidental collision with the American freighter Thompson Lykes, steaming alone from Guantanamo Bay, on what was a very dark night. Indeed, the freighter’s crew reported hitting and running down a partially submerged object which scraped along her side and keel. Moreover, Lykes’s lookouts heard people in the water crying for help in English, but the freighter did not stop, thinking she had hit a U-boat.

However, many pundits didn’t accept this official explanation, and conspiracy theories abounded, from mutiny to sabotage to being sunk by American subs USS Mackerel and/or USS Marlin (in this scenario, this was due to the Surcouf’s crew allegedly providing secret refueling assistance to a U-boat) to being a victim of the Bermuda Triangle. However, Military History Books webpage owner and retired Canadian Forces lieutenant-colonel Harold (Hal) Aage Skaarup asserts that none of the conspiracy theories hold up under scrutiny.

Of course, until the boat’s wreckage is finally discovered (if and when that ever happens), we’ll never know for certain.

Pop Culture Legacy of the Surcouf

As my fellow fans of the late, great Clive Cussler (best known for Raise the Titanic! and Sahara) are aware, the Surcouf is featured in the 2023 novel The Corsican Shadow (which was actually written by Clive’s son Dirk three years after his dad’s untimely passing), wherein the Surcouf is the subject of an underwater search by the fictional version of the National Underwater Marine Agency (NUMA) and international terrorists. (Spoiler alert: In this novel, the star-crossed warship’s wreck is discovered “…some eighty miles off the Panama coast.” For storyline purposes, the author attributes the sinking to Surcouf’s radio antenna being damaged in the collision with the Thompson Lykes followed by the reported attack of a Northrop A-17 bomber the next morning.)

About the Author: Christian D. Orr

Christian D. Orr was previously a Senior Defense Editor for National Security Journal (NSJ) and 19FortyFive. He is a former Air Force Security Forces officer, Federal law enforcement officer, and private military contractor (with assignments worked in Iraq, the United Arab Emirates, Kosovo, Japan, Germany, and the Pentagon). Chris holds a B.A. in International Relations from the University of Southern California (USC) and an M.A. in Intelligence Studies (concentration in Terrorism Studies) from American Military University (AMU). He has also been published in The Daily Torch, The Journal of Intelligence and Cyber Security, and Simple Flying. Last but not least, he is a Companion of the Order of the Naval Order of the United States (NOUS). If you’d like to pick his brain further, you can ofttimes find him at the Old Virginia Tobacco Company (OVTC) lounge in Manassas, Virginia, partaking of fine stogies and good quality human camaraderie.

Image: Wikimedia Commons.

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