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 was 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. The design entered service as the Hajen class, the first of which was completed in 1917.[2]: 103 [3]: 114
In 1921, the Hajen-class design was improved, primarily by lengthening it by 3 metres (9.8 ft) and having less powerful engines. The final Bävern-class design featured a length of 57.05 metres (187 ft 2 in), beam of 5.82 metres (19 ft 1 in), and a draught of 3.51 metres (11 ft 6 in), and a complement of 31. 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 diesel engines and two electric motors which produced 2,100 brake horsepower (1,600 kW) and 520 horsepower (390 kW) through two propellers. While surfaced, the boats had a maximum speed of 15.2 knots (28.2 km/h; 17.5 mph) and displaced 472 tons and had a speed of 8.2 knots (15.2 km/h; 9.4 mph) and displaced 650 tons while submerged.[2]: 102-103
The three submarines were all launched in 1921, built either at the Kockums yard in Malmö, or the Karlskrona Navy Yard.[1]: 362 The boats operated throughout the inter-war period and most of World War II. In 1943, Illern sank following a collision and was scrapped. Her sister ships, Bävern and Uttern, were retired in 1944.[3]: 114
Swedish Navy