German submarine U-1233

German submarine U-1233 was a Type IXC/40 U-boat built for Nazi Germany's Kriegsmarine during World War II.

Design
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-1233 had a displacement of 1144 t when at the surface and 1257 t while submerged. The U-boat had a total length of 76.76 m, a pressure hull length of 58.75 m, a beam of 6.86 m, a height of 9.60 m, and a draught of 4.67 m. The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4400 PS for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1000 shp for use while submerged. She had two shafts and two 1.92 m propellers. The boat was capable of operating at depths of up to 230 m.

The submarine had a maximum surface speed of 18.3 kn and a maximum submerged speed of 7.3 kn. When submerged, the boat could operate for 63 nmi at 4 kn; when surfaced, she could travel 13850 nmi at 10 kn. U-1233 was fitted with six 53.3 cm torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm SK C/32 naval gun, 180 rounds, and a 3.7 cm Flak M42 as well as two twin 2 cm C/30 anti-aircraft guns. The boat had a complement of forty-eight.

Service history
U-1233 was ordered on 14 October 1941 from Deutsche Werft AG in Hamburg-Finkenwerder under the yard number 396. Her keel was laid down on 29 April 1943 and was launched on 23 December 1943. About three months later she was commissioned into service under the command of Korvettenkapitän Hans-Joachim Kuhn (Crew 31) in the 31st U-boat Flotilla on 22 March 1944.

After completing training and work-up for deployment U-1233 was transferred to the 33rd U-boat Flotilla for front-line service on 1 November 1944. The U-boat left Horten Naval Base on 11 December 1944 for the first and only war patrol. After returning to Kiel, Kuhn was relieved as commander by Oberleutnant zur See Heinrich Niemeyer (Crew X/39) on 15 April 1945. In May 1945 U-1233 transferred to Fredericia in order to surrender to Allied forces. En route U-1233 and two accompanying U-boats - GS U-155 (1941) and GS U-680 - were attacked by Allied aircraft. In the course of the attack one P-51 Mustang of No. 126 Squadron RAF was shot down.

In June 1945 the surrendered U-boats were transferred to Wilhelmshaven under British guard from where they sailed for Loch Ryan, a collecting point for Operation Deadlight. On 28 December 1945 U-1233 was towed to sea by HMS Freedom (W139). When the cable slipped the U-boat was sunk by artillery fire from HMS Onslaught (G04) on 29 December 1945 in position 54.85°N, -8.9°W