Vesikko is a submarine (the only ship in its class), launched on May 10, 1933 in Creighton-Volcan in Turku. Until 1936 it was called by the production code name CV 707. Vesikko was ordered by the Dutch engineering company Ingenieurskantoor voor Scheepsbouw (a German front company) in 1930 as an industrial prototype submarine. Purchased by the Finns before the war, it saw service in the Winter and World War II by sinking the Soviet merchant ship Vyborg as its only victory. After the ceasefire with the Allies in 1944, Vesikkoby was retired. After the war, Finland was forbidden to operate submarines and was kept in storage until it became a museum ship.
Vesikko was one of five submarines in the Finnish Navy. The other four were three large Vetehinen -class boats Vetehinen , Vesihiisi , Iku-Turso and small Saukko . The word "vesikko" is the Finnish name for the European mink .
Ingenieurskantoor voor Scheepsbouw (IvS), a German shell company in the Netherlands, created for the secret design of a new German submarine fleet. Under the terms of the Treaty of Versailles after World War I, Germany was prohibited from building and operating submarines among other "offensive" weapons. This led to the transfer of arms research to foreign countries. For example, German tanks and aircraft were tested and developed in the Soviet Union. Therefore, unlike other submarines in the Finnish Navy, Vesikko was not part of the naval act. Instead, it was part of the secret restoration of the German Navy, the Reichsmarin.
The goal of the Germans was to develop a modern type of submarine to be used during the general mobilization; technology and standards were to be new and not based on World War I projects. Two prototypes were built for this purpose: E1 in Spain and CV 707 in Finland. The latter was later chosen as the first type of submarine for the new fleet. The construction of both experimental submarines was funded by Reichsmarine.
Commander Karl Bartenbach, who retired from active service in the Reichsmarine, worked as a secret liaison officer in Finland. His official title was Naval Expert of the Finnish Armed Forces, and it was under his leadership that 496-ton class Vetehinen and 100-ton class Saukko were built in Finland. Both types of submarines were developed by IvS. For the German Navy, his mission was to supervise the development and construction of a 200-250-tonne submarine, which would still be equal to the combat efficiency of the Vetehinen class. The entire mission was named Project Lilliput.
The official decision to build the Vesikko in Finland was made in 1930 after several meetings with the Finnish government. As the Lilliput Project violated the terms of the Treaty of Versailles, the agreement made no mention of Germany, and it was decided that the new submarine could only be sold to countries in the League of Nations. Potential buyers should also have had the right to own such weapons. The Government of Finland received the initial rights to purchase the submarine.
Construction of the CV 707 began in 1931 at the Creighton-Vulcan dock in Turku. At the time of its construction, the CV 707 was one of the most advanced submarine projects. For example, the maximum depth was twice as deep as the earlier German submarines and its hull could be completely built by electric welding. By removing rivets, water pressure resistance was increased, oil leaks were reduced and the construction process was faster. The Germans tested the CV 707 at Turku Archipelago in 1933-34.
Vesikko was the prototype for the German Type II submarines. Six Type IIA submarines (from U-1 to U-6), which were almost identical to the Vesicco, were built at the Deutsche Werke dock in Kiel and 44 Type IIB, IIC and IID submarines were built before and during World War II.
According to an agreement between the Finnish Ministry of Defence and Crichton-Vulcan, Finland was able to make an initial purchase before 1937, and the Finnish government switched to the submarine in August 1934. After the Finnish Parliament approved the purchase in 1936, the submarine joined the Finnish Navy under the name of Vesikko.