SM U-23 (Austria-Hungary)

When it became apparent to the Austro-Hungarian Navy that the First World War would not be a short one,[1] they moved to bolster their U-boat fleet by seizing the plans for the Danish Havmanden class submarines,[2] which had been designed by Whitehead & Co. in Fiume, who had built three units.[6] Although the Austro-Hungarian Navy was not happy with the design, which was largely obsolete,[4][7] it was the only design for which plans were available and which could be begun immediately in domestic shipyards.[7] The Austro-Hungarian Navy unenthusiastically placed orders for U-23 and her three sister boats on 27 March 1915.[1]

U-23 was one of two boats of the class to be built at the Hungarian UBAG yard in Fiume.[2] Due to demands by the Hungarian government,[1] subcontracts for the class were divided between Hungarian and Austrian firms,[3] and this politically expedient solution worsened technical problems with the design, resulting in numerous modifications and delays for the class in general.[2]

U-23 was an ocean-going submarine that displaced 173 tonnes (191 short tons) surfaced and 210 tonnes (231 short tons) submerged and was designed for a complement of 18. She was 127 feet 2 inches (38.76 m) long with a beam of 13 feet (4.0 m) and a draft of 9 feet (2.7 m). For propulsion, she featured a single shaft, a single 450 bhp (340 kW) diesel engine for surface running, and a single 160 shp (120 kW) electric motor for submerged travel.[3] She was capable of 12 knots (22 km/h) while surfaced and 9 knots (17 km/h) while submerged. Although there is no specific notation of a range for U-23, the Havmanden class, upon which the U-20 class was based, had a range of 1,400 nautical miles (2,600 km) at 10 knots (19 km/h), surfaced, and 23 nautical miles (43 km) at 8 knots (15 km/h) submerged.[6]

U-23 was armed with two 45 cm (17.7 in) torpedo tubes located in the front and carried a complement of two torpedoes. She was also equipped with a 66 mm (2.6 in)/26 deck gun and an 8 mm (0.31 in) machine gun.[3]

U-23 was launched on 5 January 1917,[3] but It is not known with certainty when U-23 was commissioned. Author Paul Halpern reports that U-23 and her three sisters all entered service between August and November 1917.[4] Although there are no specific reports of problems with U-23, the U-20 class as a whole suffered from unreliable engines which compounded the poor handling characteristics of the boats.[4] On 21 February 1918,[8] Linienschiffsleutnant Klemens Ritter von Bezard, U-23's only commanding officer,[5] was guiding the boat in an attack on the Italian transport Memfi in the Straits of Otranto. U-23 came under attack by the Italian torpedo boat Airone which first tried to ram the U-boat, and then deployed an explosive paravane. When the paravane contacted the submerged U-23, it exploded, blowing debris into the air and sinking the submarine with all hands.[8] Like all of her sister boats,[2] U-23 had no wartime successes.[5]