O23 (Dutch)

Build Group: O21
Fate: Decommissioned on 1 December 1948.
Sold to be broken up for scrap in April 1949.

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Built as K XXIII at the Rotterdamsche Droogdok Maatschappij, Rotterdam. During construction she was renamed O23

Following the German invasion of 10 May 1940, O23 was hastily commissioned, still incomplete, and sailed for England 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. 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 in 1948, being sold for scrap in April of the following year.


12-10-1937 : Laid down
05-12-1939 : Launched
13-05-1940 : Commissioned and departed the Lekhaven in Rotterdam bound for the U.K
16-05-1940 : Arrived at Portsmouth along with HrMs O9, HrMs O10, HrMs O23 and HrMs O24.
09-10-1940 : Grounded at 70 feet. She immediately surfaced and it was noticed that she was much nearer to the coast than thought due to the current. She dived again and remained close inshore during the day. No major damage was caused to the submarine.
25-01-1941 : At 1510 hours, a loud explosion was heard on board the submerged O23. Three minutes later a second loud explosion was heard. It might have been that O23 was attacked by an aircraft. Lt.Cdr. van Erkel took O23 deep.
27-02-1941 : Late in the afternoon, off Milford Haven O21, O23 and their escort the Free French minesweeper FFS La Moqueuse encounter the British merchant Losada. As La Moqueuse was more than a mile behind both submarines the crew of the Losada think they were German U-boats and opened fire. To prevent being hit both submarines crash dive. The crew of La Moqueuse had not seen both submarines dive and was now also under the impression that a German U-boat was nearby and dropped three depth charges. O 21 was the target of the attack but sustains no damage. Both submarines surfaced shortly afterwards.
30-06-1941 : Made a torpedo attack on a small merchant that was in ballast. Two torpedoes were fired that both missed their target.

Later on this day O23 torpedoed and sank the Italian tanker Capacitas about 7 nautical miles northwest of Cape Sant Vincent, Italy.
16-08-1941 : Attacks an Italian convoy with two torpedoes in the Tyrrhenian Sea. Both torpedoes missed.
01-04-1942 : O23 encounters a submarine southwest of Sardinia, Italy. Before an attack could be started the other submarine submerged. O23 did the same and for an hour she hunted the other submarine but no contact could be made.

The other submarine was the Italian Aradam that dived immediately upon seeing another submarine as it was not certain if it was a friendly or an enemy submarine
27-07-1942 : Damaged the small Japanese merchant Shofuku Maru No.2 with gunfire about 10 nautical miles southwest of Penang, Malaya.
29-07-1942 : Fired four torpedoes at the Japanese heavy cruisers Kumano and Suzuya escorted by the destroyers Oyashio, Hayashio and Kuroshio in the Straits of Malacca about 10 nautical miles west-southwest of Pulau Perak. The torpedoes missed their targets and O23 is depth charged but manages to escape without damage.
02-08-1942 : Attacked a Japanese convoy and torpedoed and heavily damaged the Japanese army cargo ship Zenyo Maru about 30 nautical miles northwest of Penang, Malaya. The Japanese ship burns out and was later towed to Singapore. She was declared a total loss.
09-09-1942 : Made a torpedo attack on a Japanese merchant vessel about 40 nautical miles southwest of Phuket. Two torpedoes were fired but both missed their target.
25-10-1942 : Torpedoed and damaged the Japanese merchant Shinyu Maru off Penang, Malaya.
14-05-1943 : O23 is slightly damaged when the Dutch accommodation/depot ship Plancius slips her moorings during strong winds. O23 was moored alongside and was damaged by a buoy. A diver found some damage to the submarine which required her to dock for repairs.
25-06-1943 : O23 carries out Special Operation Gustavus II. A rendezvous, south of the Sembilan Islands, was made with a junk to transfer 2 British army officers and 3 Chinese. Some of the crew of the junk were taken on board O23 for return passage to Colombo
26-06-1943 : Made a torpedo attack on a small empty Japanese tanker near the One Fathom Bank in the Malacca Straits. All torpedoes missed.
04-08-1943 : O23 carries out Special Operation Gustavus III. A rendezvous, south of the Sembilan Islands, was made with the same junk as on 25 June 1943 to transfer personnel.
05-08-1943 : O23 sights a ship very nearby about 30 nautical miles south-southwest of Penang. The torpedo tubes could not be brought to the ready quickly enough for an attack so O23 surfaced and gave chase, but she was spotted by the enemy and attacked with gunfire. O23 submerged and was depth charged by an escort vessel but she suffered no damage and was able to slip away.
01-12-1948 : Decommissioned


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