Germany was stripped of her U-boats by the Treaty of Versailles at the end of World War I, but in the late 1920s and early 1930s began to rebuild her armed forces. The pace of program accelerated under Adolf Hitler, and the first Type II U-boat was laid down on February 11, 1935. Knowing that the world would see this step towards rearmament, Hitler reached an agreement with Britain to build a navy up to 35% of the size of the British Royal Navy in surface vessels, but equal to the British in number of submarines. This agreement was signed on June 18, 1935, and U-1[?] was commissioned 11 days later.
The defining characteristic of the Type II was its tiny size. Known as the Einbaum ("dugout canoe"), it had the advantages over larger boats of the ability to work in shallow water, diving more quickly, and being more difficult to spot due to the low conning tower. However, it had a shallower maximum depth, short range, and cramped living conditions, and could carry few torpedoes.
The boat had a single hull, with no watertight compartments. There were three torpedo tubes forward (none aft), with space for another two torpedoes inside the pressure hull for reloads. A single 20mm gun was provided for defence against aircraft, but no deck gun was mounted.
Space inside was limited. The two spare torpedoes extended from just behind the torpedo tubes to just in front of the control room, and most of the 24-man crew lived in this forward area around the torpedoes, sharing 12 bunks. Four bunks were also provided aft of the engines for the engine room crew. Cooking and sanitary facilities were basic, and in this environment long patrols were very arduous.
Most Type IIs only saw operational service during the early years of the war, thereafter remaining in training bases. Some, however, were stripped down to just a hull, transported by barge and road vehicle to Linz, and reassembled in the Black Sea for use against Russia.
In contrast to other German submarine types, few Type IIs were lost. This, of course, reflects their use as training boats, although accidents accounted for several vessels.
These boats were a first step towards re-armament, intended to provide Germany with experience in submarine construction and operation and lay the foundation for larger boats to build upon. They were very effective within their intended role.
Deutsche Werke AG[?], of Kiel built six Type IIAs in 1934 and 1935.
Deutsche Werke AG[?], of Kiel, built four Type IIAs in 1935 and 1936, Germaniawerft AG[?], of Kiel, built fourteen in 1935 and 1936, and Flender-Werke AG[?], of Lübeck, built two between 1938 and 1940, for a total of twenty built.
U-7[?] -- U-8[?] -- U-9[?] -- U-10[?] -- U-11[?] -- U-12[?] -- U-13[?] -- U-14[?] -- U-15[?] -- U-16[?] -- U-17[?] -- U-18[?] -- U-19 -- U-20 -- U-21[?] -- U-22[?] -- U-23[?] -- U-24[?] -- U-120[?] -- U-121[?]