SM U-2 (Austria-Hungary)

SM U-2 or U-II was a U-1-class submarine or U-boat built for and operated by the Austro-Hungarian Navy (Kaiserliche und Königliche Kriegsmarine or K.u.K. Kriegsmarine). U-2 was designed by American Simon Lake's Lake Torpedo Boat Company and built at the navy yard in Pola. She was one of two Lake-designed submarines purchased as part of a competitive evaluation of three foreign submarine designs.

U-2 was launched in April 1909 and was 100 ft long and displaced almost 230 t surfaced and just under 249 t when submerged. The Austro-Hungarian Navy conducted trials for U-2 through 1910. The U-boat was originally powered by two gasoline engines for surface running, and two electric motors when submerged, but during her evaluation period, the gasoline engines were found to be incapable of reaching the contracted speed. U-2 was commissioned in June 1911 and served as a training boat for the Austro-Hungarian Navy through 1914.

At the beginning of World War I, U-2 was not operational because she was in drydock awaiting replacement diesel engines. With her new engines and a new conning tower installed by June 1915, U-2 conducted reconnaissance cruises out of Trieste but was declared obsolete in early 1918. U-2 remained in service as a training boat at the submarine base on Brioni, but was at Pola at the end of the war. She was ceded to Italy as a war reparation in 1920 and scrapped at Pola. U-2 did not sink any ships during the war.

Design and construction
U-2 was built as part of a plan by the Austro-Hungarian Navy to competitively evaluate foreign submarine designs from Simon Lake, Germaniawerft, and John Philip Holland. The Austro-Hungarian Navy ordered plans for U-2 (and sister ship U-1) in 1906 from the Lake Torpedo Boat Company of Bridgeport, Connecticut. U-2 was built at the Pola Navy Yard and was launched on 3 April 1909.

U-2 had several features typical of Lake's designs, including a diving chamber under the bow and two variable pitch propellers. Lake's design also called for two retractable wheels that allowed travel over the seabed. The design also placed the diving tanks above the waterline of the single, cylindrical hull, which necessitated a heavy ballast keel for vertical stability. This arrangement required mechanical pumping, a procedure that took 8 minutes. U-2's propulsion system consisted of two gasoline engines for surface running and two electric motors for running while submerged.

The boat was 100 ft long by 15 ft abeam and had a draft of 12 ft. As designed, her displacement was 229.7 LT surfaced and 248.9 LT submerged. She was outfitted with three 45 cm torpedo tubes—two in the bow, one in the stern—and could carry up to five torpedoes, but typically carried three. U-2 was also armed with a 3.7 cm deck gun.

Service career
Upon U-2's completion, the Austro-Hungarian Navy conducted trials of the submarine throughout most of 1910. U-2's gasoline engines were never able to meet the speed called for in the contract during the Navy evaluations, and were considered not suitable for wartime use. As a result, the Navy only paid for U-2's hull and armament, and arranged a lease of the gasoline engines while replacement diesel engines were ordered from the Austrian firm Maschinenfabrik Leobersdorf. Despite the engine problems, U-2 and her sister ship had the best performance in diving and steering amongst the U-boats under evaluation by the Navy.

U-2 was commissioned into the Austro-Hungarian Navy on 22 June 1911 under the command of Linienschiffsleutnant Klemens Ritter von Bézard. U-2 served as a training boat through 1915, conducting up to ten training cruises per month. At the outbreak of World War I, she was in drydock awaiting the installation of her new diesel engines. To accommodate the new engines, she was lengthened by about 11 in. The modifications and new engines lowered her surface displacement to 223.0 t but increased her submerged displacement to 277.5 t.

From January to June 1915, U-2 underwent a refit and received a new conning tower. She was stationed at Trieste in mid July and conducted reconnaissance cruises from that port. On 11 January 1918, she was declared obsolete, but was retained as a training boat at the submarine base on Brioni. U-2 was at Pola at the war's end, and was scrapped after her cession to Italy as a war reparation in 1920. U-2 did not sink any ships during the war.