The French Cruiser Submarine "Surcouf" (1929)
Among the efforts to curtail an arms race following World War One, the 1922 Washington Naval Treaty - signed by the British Empire, France, Italy, Japan and the United States - limited the construction of warships among its signatories, specifically for battleships, battlecruisers and aircraft carriers (which were an emerging concept at the time).
However, the first version of that treaty did not explicitely limit the construction of submarines (save for a maximum displacement of 10000 tons) and soon enough the French authorities ordered the construction of a "submarine cruiser", as a way to circumvent some of those limitations (and mostly because French shipbuilders were already quite experienced with designing cutting-edge submarines).
The "Surcouf" was designed following the requirements that it should be able to carry provisions for 90 continuous days of high-seas deployment, and feature firepower comparable to that of a battlecruiser. Indeed, the submarine was built around a turret sporting two 203mm guns - which were the largest caliber allowed by the Washington Naval Treaty. According to the specifications, it could fire up to a distance of 16 kilometers with its own instruments, and 26 kilometers with aircraft support. To this end, the Surcouf was also the first submarine designed to carry a reconnaissance aircraft. Initially an improved version of the Besson MB.35 floatplane designated MB.411 was chosen for that task {images 3 and 4}, but a bespoke gyroplane was later devised to replace it in the form of the Dorand G.20 {image 5} - although development for it never came to fruition with the fall of France in 1940.
Launched in 1929 and commissionned in 1934, the Surcouf would remain the largest submarine in the world until the launch of the Japanese I-400 class in 1944 - namely because the 1930 London Naval Treaty specifically regulated submarine warfare in order to address the topics that the Washington Naval Treaty did not cover. In particular, submarines were now limited to 2000 tons - with each major nation allowed to operate three units of up to 2800 tons. However, the Surcouf and its 3250 tons of displacement was exempted by the terms of this treaty as the sole exception, mostly on the basis that it was already operational at this point.
At the time of the Battle of France in 1940, Surcouf was being refitted in Brest and managed to escape to the United Kingdom and ultimately remained under the control of the Free French forces. In February 1942, the submarine departed Halifax, Canada, with the intent of rallying Australia and was sunk on the way to the Panama Canal during the night of the 18th to 19th of the same month. The circumstances of her sinking are unclear, although the most likely scenario points towards American forces being responsible after confusing her with an enemy ship.
- Covert Shores : Surcouf, The Ultimate Interwar Cruiser Submarine
- Drachinifel : MN Surcouf - Guide 136 (Extended)
- (1) Marine & Océans : Chronique Navale du 18 Février
- (2) Aviation Navale Française 1939 - 1940 : Sous-Marin Surcouf
- (3) & (4) Aviation Navale Française 1939 - 1940 : Besson MB.411 "Petrel"
- (5) Old Machine Press : Dorand Gyroplane G.20 (G.II)
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