O 23 was a built for the Royal Netherlands Navy during the 1930s for European service. Completed in 1940, she sank several ships during World War II in the Mediterranean and in the Indian Ocean.
Design and description The O 21-class submarines were slightly smaller versions of the preceding since they lacked that class's minelaying capability. The boats had a length of overall, a beam of and a draft of .Bagnasco, p. 240 They displaced on the surface and submerged. The submarines had a crew of 60 officers and enlisted men.van Willigenburg, p. 69
For surface running, the boats were powered by two Sulzer diesel engines, each driving one propeller shaft. When submerged each propeller was driven by a electric motor. They could reach on the surface and underwater. On the surface, the boats had a range of at and at 9 knots submerged. The submarines had a diving depth of .
The O 21 class was armed with eight torpedo tubes. Four of these were in the bow and two tubes were in the stern. The other pair were on an external rotating mount amidships. A reload was provided for each internal torpedo tube. They were also armed with two Bofors AA guns; these were on single watertight mounts that retracted into the conning tower when submerged.Bagnasco, p. 238
Construction and career
O 23 was ordered on 19 June 1937 and laid down on 12 October 1937 at the shipyard of Rotterdamsche Droogdok Maatschappij in Rotterdam. The boat was launched on 5 December 1939. Following the German invasion of 10 May 1940, O 23 was hastily commissioned, still incomplete, and sailed for England on 13 May, together with her sister , to be completed at the Thornycroft shipyard at Southampton.
During the war she operated in the North Sea, the Mediterranean Sea and the Indian Ocean. O 23 made twenty patrols during the war in the course of which she sank or damaged five ships. She survived the war and was decommissioned on 1 December 1948, being sold for scrap in April of the following year.
Summary of raiding history Ships sunk and damaged by O 23. Date Ship name Nationality/Type Tonnage (GRT) Fate 30 June 1941 Capacitas Italian tanker 5371 Sunk 27 July 1942 Shofuku Maru No.2 Japanese merchant ship 729 Damaged 2 August 1942 Zenyo Maru Japanese army cargo ship 6440 Damaged (burned out and later declared a total loss) 2 August 1942 Ohio Maru Japanese transport ship 5872 Sunk 25 October 1942 Shinyu Maru Japanese merchant ship 4622 Damaged
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