The submarine was ordered on 9 June 1937 and laid down on 12 October 1937 as K XXIII at the Rotterdamsche Droogdok Maatschappij, Rotterdam. During construction she was renamed O 23, and was finally 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 to be completed at the Thornycroft shipyard at Southampton.[1]
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.[1] [2]
Ships sunk and damaged by O 23.[2]
| 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 |