Ship ClassType II-class Submarine
BuilderFriedrich Krupp Germaniawerft
Yard Number553
Slip/Drydock NumberII
Ordered2 Feb 1935
Laid Down11 Apr 1936
Launched28 Aug 1936
Commissioned24 Sep 1936
Sunk10 Sep 1944
Displacement279 tons standard; 328 tons submerged
Length140 feet
Beam13 feet
Draft13 feet
MachineryTwo MWM RS 127 S 6cyl diesel engines (690bhp), two Siemens-Schuckert PG VV 322/36 double-acting elector motors (450shp), two shafts
Speed12 knots
Range3,000nm at 8 knots surfaced, 1,800nm at 12 knots surfaced, 35-43nm at 4 knots submerged
Armament3x53.3cm bow torpedo tubes, 1x2cm anti-aircraft gun, 5 torpedoes or 12 TMA mines or 18 TMB mines
Submerged Speed7 knots


ww2dbaseBuilt by Germaniawerft, U-23 was a Type IIB submarine launched and commissioned in 1936. At the start of the Atlantic War, as a member of the 1st Submarine Flotilla, she scored one of German Navy's first successes as she sank British merchant ship Glen Farg by torpedo and gunfire in the North Atlantic. After a successful stint that saw her sinking 7 merchant ships and 1 warship in the Atlantic Ocean, she was transferred to the 21st Submarine Flotilla, a training unit, in Jul 1940. In Sep 1942, she was broken up into sections and transported along the Danube River to Galați, Romania, where she was re-assembled for service in the Black Sea with the 30th Submarine Flotilla, whose home port was Constanţa, Romania. She sank a Soviet warship and several merchant ships with the 30th Submarine Flotilla. On 10 Sep 1944, she was scuttled off the Turkish coast to prevent capture by the advancing Soviet forces. Her wreck was discovered by Turkish marine engineer Selçuk Kolay at the depth of 49 meters (160 feet) near Ağva, Turkey.

ww2dbaseSource: Wikipedia

Last Major Revision: Feb 2022

Submarine U-23 Interactive Map

U-23 Operational Timeline

2 Feb 1935 The order for the construction of U-23 was issued.
11 Apr 1936 The keel of U-23 was laid down by Germaniawerft in Kiel, Germany.
28 Aug 1936 U-23 was launched by Germaniawerft in Kiel, Germany.
1 Sep 1936 U-23 was assigned to the 1st Submarine Flotilla; Korvettenkapitän Eberhard Friedrich Clemens Godt was named her commanding officer.
24 Sep 1936 U-23 was commissioned into service.
1 Oct 1937 Kapitänleutnant Otto Kretschmer was named the commanding officer of U-23, relieving Kapitänleutnant Hans-GĂźnther Looff.
1 Aug 1939 U-23 was detached from the 1st Submarine Flotilla.
24 Aug 1939 U-23 began her first war patrol.
1 Sep 1939 U-23 was officially assigned to the 1st Submarine Flotilla, although she was already at sea on her first war patrol.
4 Sep 1939 U-23 completed her first war patrol.
9 Sep 1939 U-23 began her second war patrol.
30 Sep 1939 U-23 completed her second war patrol.
1 Oct 1939 U-23 began her third war patrol.
4 Oct 1939 U-23 spotted British merchant ship Glen Farg (Master Robert Galloway Hall) at 0445 hours about 110 kilometers (about 69 miles) south-southwest of Sumburgh Head, Shetland Islands in the North Atlantic, and stopped the ship with machine gun fire. At 0600 hours, when she detected that the British was sending out distress calls, she sank the ship with one G7a torpedo and gunfire. One crew member was killed. The 16 survivors were picked up by HMS Firedrake.
16 Oct 1939 U-23 completed her third war patrol.
1 Nov 1939 U-23 began her fourth war patrol.
9 Nov 1939 U-23 completed her fourth war patrol.
5 Dec 1939 U-23 began her fifth war patrol.
7 Dec 1939 U-23 fired a torpedo at Danish ship Scotia, sailing in ballast, in the North Sea at 2326 hours. The submarine would continue to pursue into the next day.
8 Dec 1939 U-23 sank Danish merchant ship Scotia, sailing in ballast, in the North Sea with 0004 hours with one torpedo. Nineteen were killed. The two survivors were picked up by the nearby Danish merchant ship Hafnia immediately.
15 Dec 1939 U-23 completed her fifth war patrol.
8 Jan 1940 U-23 began her sixth war patrol.
11 Jan 1940 The Fredville, a 1,150-ton Norwegian steam merchant, was attacked and sunk approximately 100 miles east of the Orkney Isles at 1632 hours. There had been two explosions in the hold, the first seemed to cause little damage but 10 minutes later a much larger explosion broke the ship in two. The ship in ballast was on her way to Methil, Scotland, United Kingdom. 5 of the crew found time to get into a lifeboat and made repeated attempts to find any more survivors from the after part of the ship that remained afloat but none were found. The 5 men were picked up by a Swedish ship and taken to Kopervik, Karmøy Island, Norway. It was probable that the ship was sunk by German submarine U-23 (Otto Kretschmer), though at the enquiry held later the crew said that they thought there could have been bombs put into the coal bunkers by the Wollweber Group who were a group of Communist saboteurs who were responsible for the loss of several Scandinavian ships; they also stated that the ship was marked with the Norwegian flag and had navigation lights on.
12 Jan 1940 German submarine U-23 torpedoed and sank Danish oil tanker Danmark in Inganess Bay, Kirkwall, Orkney Islands, Scotland, United Kingdom at 0650 hours. Her crew of 40 escaped safely, but the 14,000 tons of fuel destined for the Allied war effort were lost.
15 Jan 1940 U-23 completed her sixth war patrol.
18 Jan 1940 U-23 began her seventh war patrol.
24 Jan 1940 German submarine U-23 torpedoed and sank Norwegian cargo ship Varild in the North Sea at 1900 hours, killing the entire crew of 15.
29 Jan 1940 U-23 completed her seventh war patrol.
9 Feb 1940 U-23 began her eighth war patrol.
18 Feb 1940 British Royal Navy D-class destroyer HMS Daring (H16; Commander Sydney Alan Cooper), whilst escorting Allied convoy HN-12 from Norway, was attacked by German submarine U-23 (Kapitänleutnant Otto Kretschmer) at 0354 hours. Two torpedoes struck the 1,375-ton ship and she sank immediately about 40 miles east of the Pentland Firth, Orkney Islands, Scotland, United Kingdom. 147 officers and men were lost. 1 officer and 3 ratings were picked up from a float by HMS Ingleield (D02) and taken to Scapa Flow, Scotland and another rating was found amidst the debris and rescued by the submarine HMS Thistle (N24) assisted by HMS Ilex (D61) and taken to Rosyth, Scotland.
19 Feb 1940 U-23 sank British merchant ship Tiberton with a G7e torpedo at 0405 hours in the North Sea about 33 miles east of Kirkwall, Orkney Islands, Scotland, United Kingdom. It broke in two and sank within 30 seconds, killing all 34 aboard. The ship was carrying iron ore from Norway, bound for Britain.
22 Feb 1940 In the Atlantic Ocean, German submarine U-23 sank British steamer Loch Maddy, which was damaged by U-57 and abandoned by its crew on the previous day.
1 Apr 1940 Otto Kretschmer stepped down as the commanding officer of U-23.
8 Apr 1940 Kapitänleutnant Heinz Beduhn was named the commanding officer of U-23.
10 Apr 1940 U-23 completed her eighth war patrol.
13 Apr 1940 U-23 began her ninth war patrol.
3 May 1940 U-23 completed her ninth war patrol.
20 May 1940 Oberleutnant Heinrich Driver was named the commanding officer of U-23, relieving Heinz Beduhn.
1 Jul 1940 U-23 was assigned to the 21st Submarine Flotilla.
1 Oct 1940 Oberleutnant Kurt Reichenbach-Klinke was named the commanding officer of U-23, relieving Heinrich Driver.
21 Mar 1941 Oberleutnant Ernst-Ulrich BrĂźller was named the commanding officer of U-23, relieving Kurt Reichenbach-Klinke.
24 Sep 1941 Oberleutnant Ulrich Gräf was named the commanding officer of U-23, relieving Ernst-Ulrich BrĂźller.
27 Mar 1942 Oberleutnant Rolf-Birger Wahlen was named the commanding officer of U-23, relieving Ulrich Gräf.
26 Aug 1942 U-23 was detached from the 21st Submarine Flotilla.
27 Jun 1943 U-23 began her tenth war patrol.
19 Jul 1943 U-23 completed her tenth war patrol.
10 Aug 1943 U-23 began her eleventh war patrol.
24 Aug 1943 U-23 sank Soviet patrol ship Shkval with gunfire and hand-thrown grenades and explosives about 35 kilometers (about 22 miles) south of Sukhumi, Georgia at 2315 hours. Three were killed. Seven survivors in a lifeboat reached shore at 1100 hours on the next day.
9 Sep 1943 U-23 completed her eleventh war patrol.
10 Oct 1943 U-23 began her twelfth war patrol.
15 Oct 1943 U-23 damaged Soviet minesweeping trawler TSC-486 Sovetskja Rossiya with a torpedo just off the Georgian coast at 2131 hours. U-23 attempted to follow the small three-ship convoy, but was driven away by gunfire.
23 Oct 1943 U-23 sank Soviet merchant ship Tanais, at anchor off Poti, Georgia, with a torpedo. The ship broke in two, with the stern sinking immediately, and the bow sinking a few minutes later. Eleven were killed, ten survived.
11 Nov 1943 U-23 completed her twelfth war patrol.
14 Dec 1943 U-23 began her thirteenth war patrol.
7 Jan 1944 U-23 completed her thirteenth war patrol.
30 Mar 1944 U-23 began her fourteenth war patrol.
5 Apr 1944 Soviet patrol craft SKA-099 detected German submarine U-23 just off Poti, Georgia at 0115 hours, and attacked with gunfire. U-23 responded with her 20mm gun and machine guns before escaping. SKA-099 sufered damage and would return to service later, though the Germans thought SKA-099 had been sunk.
24 Apr 1944 U-23 completed her fourteenth war patrol.
17 May 1944 U-23 began her fifteenth war patrol.
7 Jun 1944 U-23 completed her fifteenth war patrol.
20 Jun 1944 Oberleutnant Rudolf Arendt was named the commanding officer of U-23, relieving Kapitänleutnant Rolf-Birger Wahlen.
16 Aug 1944 U-23 began her sixteenth and final war patrol.
1 Sep 1944 U-23 fired three torpedoes into the harbor of ConstanĹŁa, Romania and reported three detonations at about 0333 hours. Two of them of them damaged berthing facilities, while another struck and sank the already-damaged Romanian merchant ship Oituz. U-23 departed at about 0400 hours and laid one EMS mine in the roads near Tuzla lighthouse about 10 kilometers to the south.
10 Sep 1944 U-23 was scuttled off Ağva, Turkey to prevent Soviet capture.

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