HNLMS O 23

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. They displaced on the surface and submerged. The submarines had a crew of 60 officers and enlisted men.
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 [40 mm L/60 gun| Bofors] AA guns; these were on single watertight mounts that retracted into the conning tower when submerged.

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	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
2 August 1942	Ohio Maru	Japanese transport ship	5872	Sunk
25 October 1942	Shinyu Maru	Japanese merchant ship	4622	Damaged