Finnish Submarine Vesikko - Last German Type II U-boat in the world

The Finnish submarine Vesikko, used in the Second World War, is one of the most popular attractions in the Suomenlinna Sea Fortress in Helsinki. Vesikko is also globally a significant memorial to naval warfare. Vesikko is the last surviving German Type II submarine in the world. The word "vesikko" is the Finnish word for the European mink.

Ingenieurskantoor voor Scheepsbouw (IvS), was a German front company in the Netherlands, established to secretly design a new German submarine fleet. According to the terms of the Versailles Peace Treaty after World War I, Germany was banned from building and operating submarines among other "offensive" weaponry. This resulted in moving the armaments' research to foreign countries. For example, German tanks and aircraft were tested and developed in the Soviet Union. Therefore, unlike the other submarines in the Finnish Navy, Vesikko was not part of the Naval Act. Instead, it was part of the secret rebuilding of the German Navy, the Reichsmarine. The objective of Germans was to design a modern submarine type to be used during general mobilization; technology and standards were to be new and not based on World War I designs. For this purpose two prototypes were built, E1 in Spain and CV 707 in Finland. The latter was later chosen as a first submarine type for the new fleet. Construction of both of these experimental submarines was funded by the Reichsmarine.

Commander Karl Bartenbach, who had retired from active service in the Reichsmarine, worked as secret liaison officer in Finland. His official title was Naval Expert of the Finnish Defence Forces, and it was under his leadership that the 496-ton Vetehinen class and the 100-ton Saukko were built in Finland. Both submarine types were designed by IvS. For the German Navy, his mission was to oversee the developing and construction of a 200–250 ton submarine, which would still equal the combat effectiveness of the Vetehinen class. The whole task was named The Lilliput Project. The official decision allowing Vesikko to be constructed in Finland was made in 1930 after several meetings with the Finnish Government. Since The Liliput Project broke the terms of the Versailles Peace Treaty, there was no mention of Germany in the agreement, and it was decided that the new submarine could only be sold to nations belonging to the League of Nations. The would-be buyers also had to have the rights to own such a weapon. The Finnish Government gained primary rights to purchase the submarine.

The construction of CV 707 begun in 1931 at the Crichton-Vulcan dock in Turku. At the time of its construction, CV 707 was one of the most advanced submarine designs. For example, the maximum depth was over twice that of earlier German submarines, and its hull could be built completely by electric welding. By eliminating rivets there was increased resistance to water pressure, decreased oil leakages, and the construction process was faster. The submarine was built in Turku and launched in May 1933. It was designed by Dutch Ingenieurskantoor voor Scheepsbouw den Haag (I.v.S) and built in 1933 by the Crichton-Vulcan shipyard in Turku, Finland. It was part of the secret rebuilding of the German Navy. After its construction, CV 707 became one of the most advanced submarine designs of its time.

Vesikko was a prototype for the German Type II submarines. Six Type IIA submarines (U-1 to U-6) which were almost identical to Vesikko were built in the Deutsche Werke dock in Kiel, and after these, 44 Type IIB, IIC, and IID submarines were built before and during World War II. Between the years 1933 and 1934 the German Navy carried out trials with the submarine in the Turku Archipelago. In 1936, the Finnish Navy bought it and named it as Vesikko.

Vesikko belonged to the Finnish Navy as one of five submarines in the 1930s and 1940s and undertook patrols in the Gulf of Finland during the Winter and Continuation Wars (1939–1944). The base for Finnish submarines was in the dock area of Suomenlinna. Vesikko was one of five submarines to serve the Finnish Navy. The other four were the three larger Vetehinen-class boats Vetehinen, Vesihiisi, Iku-Turso and the small Saukko (”otter” in Finnish). Like other submarines of the Finnish Navy, she operated and patrolled the Gulf of Finland in convoy, safety and patrol duties during the Winter War against the Soviet Baltic Fleet. On December 1 and 19 December 1939, Vesikko made attempts to attack the Soviet heavy cruiser Kirov and battleship Marat, both of which had been damaged by Finnish coastal batteriers. When the Continuation War started on 25 June in 1941, all submarines were ordered to patrol the eastern part of the Gulf of Finland. On 3 July 1941 Vesikko sank a Soviet merchant ship named Vyborg east of Suursaari island. During Continuation War until her end, Vesikko operated making patrols, escorting to convoys and evacuating people from at the end of war.

https://www.suomenlinna.fi/en/visitor/museums/vesikko/