Sea of Iron:
Finnish Submarines

By Mike Bennighof, Ph.D.
November 2018

Finland first obtained a navy of sorts during the Finnish Civil War of 1919, when a number of elderly gunboats and torpedo boats of the Tsarist Navy fell into White Finnish hands. Almost all of these captures came in shipyards and harbors where the vessels had been laid up without crews, and not of active warships. The only serious losses came when ice trapped and crushed several torpedo boats in Viipuri Bay.

By the early 1920s, these ships had become thoroughly worn out and most of them went to the scrapyard in Turku. The fleet’s first commander, Commodore Hjalmar von Bonsdorff, presented a plan in 1919 for a navy base around a division of armored coast defense ships, with a squadron of large destroyers and 40 torpedo boats, plus submarines and minelayers. It went nowhere, but the basic concept, heavy guns supported by submarines and torpedo craft, stayed with the next generation of Finnish naval planners.

The Finns saw two threats requiring a fleet: a possible Soviet landing around Helsinki, and another Swedish attempt to seize the Åland Islands (repeating their 1918 adventures in the Finnish archipelago, driven off by German threats). The Finnish parliament finally passed an ambitious naval construction program in September 1927 after two years of debate. That didn’t stop the navy from signing a contract for its first submarine a full year before the Navy Act became law, and another for two more in April 1927.

Loading torpedoes aboard Vesikko.
The program called for two armored gunboats, three high-seas submarines, one tiny submarine intended for operations on Lake Ladoga, and four motor torpedo boats. A never-completed second phase would have added four more armored ships, six 1,000-ton destroyers, nine high-seas submarines and three more tiny lake submarines.

Crichton-Vulcan of Turku, a conglomerate (by Finnish standards) formed from the 1924 merger of two financially-troubled shipyards, received most of the Navy’s contracts. They built the submarines to a design from the Dutch firm Ingenieurskantoor voor Scheepsbouw (I.v.S), a front for the German shipyards AG Vulkan and Krupp-Germaniawerft which under the terms of the Versailles Treaty could not participate in submarine construction. The Vetehinen, Vesihiisi and Iku-Tursu were 500-ton minelaying submarines that became prototypes for the much larger German Type VII u-boat, the backbone of the Kriegsmarine’s submarine force during World War II.

Launch ceremonies for Iku-Tursu.

German engineers oversaw the construction, which proceeded slowly. When the Finnish shipyard workers went on strike, Crichton-Vulcan imported German craftsmen to replace them. After delivery, German officers (some of them active-duty officers like Kapitan-Leutnant Karl Topp, future commander of the battleship Tirpitz) remained on hand for “testing” but in reality trained the new Finnish crews. Meanwhile, the future Finnish submarine commanders served on board Italian boats to gain experience.

The declining Hietalahden Laivatelakka yard in Helsinki laid down the tiny submarine Saukko in 1930, with a claimed displacement of 99 tons. The Treaty of Dorpat signed in 1920 between Finland and the Soviet Union limited warships on Lake Ladoga to 100 tons, but as built Saukko actually displaced 114 tons. She had two torpedo tubes with no reloads, and could be divided into two segments for transport by rail. Saukko never actually served on the lake, but was used in the Gulf of Finland. Also an I.v.S. design, Saukko was to be the prototype for a coast-defense submarine the Germans could build rapidly and in large numbers. They discarded this concept even before the Finns laid down Saukko, and in service she proved a disappointment. She was prone to break down, and her small size made her very difficult to handle in the Baltic.

The tiny submarine Saukko.
In 1932, Crichton-Vulcan laid down another I.v.S-designed submarine “on speculation” (that is, without a contracted buyer) but actually at the secret request of the German Reichsmarine. This boat, known initially as CV707, had almost the same torpedo armament as the bigger Vetehinen (five torpedo tubes as opposed to six) but displaced half as much, sacrificing most of her range. She was based on the German World War One UBII type, and became the basis for the Second World War’s Type II German coastal submarine.

She completed in 1933, and for the next three years I.v.S. and Crichton “engineers” (German submarine officers in civilian attire) “tested” the submarine, undertaking training cruises in the Baltic. Germany began submarine construction in late 1934 and announced the step in March 1935 with the first boats commissioning that summer. With training moved to CV707’s German-built sisters, the secret training submarine was no longer needed and Crichton sold her to the Finnish Navy in 1936.

The Finns liked Vesikko, as they named the boat, and hoped to build more of the same type. Her relative lack of range meant little in the congested waters of the Gulf of Finland and Baltic Sea. Along with a third armored gunboat and a half-dozen small destroyers, the Finnish Navy hoped to build at least three more of this type in the years just before World War II but could not obtain funding.

Finland’s five submarines all survived the war, and Vesikko remains today as a war memorial. They formed the fleet’s offensive striking power, but during the Winter War could not prevent Soviet battleships and cruisers from shelling the Finnish lines. Tiny Saukko made the first attempt, stalking first the flotilla leader Minsk and then the battleship Oktyabryskaya Revoluciya on 10 December 1939 but having to call off the attack when her air vents froze.

Finnish submariners had little ice experience.

Ice proved a serious problem — despite a design requirements that the Vetehinen class hulls be strengthened to resist ice, the Finnish Navy had not trained its submarine crews for sub-zero operations. The minelaying submarines began placing illegal offensive minefields in neutral Estonian waters, the Finnish government reasoning that since the Soviets were violating Estonian neutrality, they would reply. But Vesihiisi and Vetehinen were both damaged by ice on these missions, and on 15 January the fleet command ordered a halt to all submarine operations.

The Finns opened the Continuation War in June 1941 by laying heavy mine barrages across the Gulf of Finland, and this kept Soviet surface ships penned in until 1944. In the summer of 1942 the Red Navy began a submarine offensive in the Baltic, and the Finnish large submarines were tasked with hunting them. On 21 October Vesihiisi sank the Soviet submarine S-7, on the 26th Iku-Tursu sank Shch-320, and on 5 November Vetehinen rammed and sank Shch-305. These would be Finland’s first and last submarine successes. After the war, Finland was forced to give up her submarines, keeping only Vesikko as a permanent memorial.

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Mike Bennighof is president of Avalanche Press and holds a doctorate in history from Emory University. A Fulbright Scholar and award-winning journalist, he has published over 100 books, games and articles on historical subjects. He lives in Birmingham, Alabama with his wife, three children and his dog, Leopold.