|Ordered:||14 October 1941|
|Builder:||Deutsche Werft AG, Hamburg|
|Laid down:||29 April 1943|
|Launched:||23 December 1943|
|Commissioned:||22 March 1944|
|Fate:||sunk 29 December 1945 in position Coordinates:|
|Class and type:||Type IXC/40 submarine|
|Height:||9.60 m (31 ft 6 in)|
|Draught:||4.67 m (15 ft 4 in)|
|Test depth:||230 m (750 ft)|
|Complement:||4 officers, 44 enlisted|
|Identification codes:||M 49 604|
German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-1233 had a displacement of 1,144 tonnes (1,126 long tons) when at the surface and 1,257 tonnes (1,237 long tons) while submerged. The U-boat had a total length of 76.76 m (251 ft 10 in), a pressure hull length of 58.75 m (192 ft 9 in), a beam of 6.86 m (22 ft 6 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.67 m (15 ft 4 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged. She had two shafts and two 1.92 m (6 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).
The submarine had a maximum surface speed of 18.3 knots (33.9 km/h; 21.1 mph) and a maximum submerged speed of 7.3 knots (13.5 km/h; 8.4 mph). When submerged, the boat could operate for 63 nautical miles (117 km; 72 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 13,850 nautical miles (25,650 km; 15,940 mi) at 10 knots (19 km/h; 12 mph). U-1233 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 180 rounds, and a 3.7 cm (1.5 in) Flak M42 as well as two twin 2 cm (0.79 in) C/30 anti-aircraft guns. The boat had a complement of forty-eight.
U-1233 was ordered in 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.
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 - U-155 and 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