During World War I, Sweden primarily relied on the Swedish Navy to enforce the nation's neutrality. The Riksdag invested in the fleet during the war, including submarines. Swedish doctrine viewed submarines as a cheap method to counter enemy capital ships, although the Navy often wanted more boats.[1]: 355 In the middle of the war, Swedish naval officials were impressed by the performance of German U-boats. As a result, Kockums bought a license to the Type UB-III U-boat from AG Weser. Kockums modified the design by removing the rear torpedo tube and shortened the hull before it was offered to the Navy, who ordered three boats.[2]: 103 [3]: 114
The design featured a length of 54.00 metres (177 ft 2 in), beam of 5.21 metres (17 ft 1 in), and a draught of 3.51 metres (11 ft 6 in), and a complement of 30. Armament consisted of four 457 mm (18.0 in) torpedo tubes and a 75 mm (3.0 in) deck gun. The boats were propelled by two 6-cylinder diesel engines and two electric motors which produced 2,000 brake horsepower (1,500 kW) and 700 horsepower (520 kW) through two propellers. While surfaced, the boats had a maximum speed of 15.5 knots (28.7 km/h; 17.8 mph) and displaced 422 tons and had a speed of 9 knots (17 km/h; 10 mph) and displaced 600 tons while submerged.[1]: 362 In 1921, the vessels was followed up by the three Bävern-class submarines, which was slightly longer and featured an improved design.[2]: 103
After entering service by 1918, the boats operated throughout the interwar period and most of World War II, and were all decommissioned by 1943.[1]: 362
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Swedish Navy