were considerably larger than the original Type IXs. U-181 had a displacement of when at the surface and while submerged. The U-boat had a total length of, a pressure hull length of, a beam of, a height of, and a draught of. The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines plus two MWM RS34.5S six-cylinder four-stroke diesel engines for cruising, producing a total of for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of for use while submerged. She had two shafts and two propellers. The boat was capable of operating at depths of up to. The submarine had a maximum surface speed of and a maximum submerged speed of. When submerged, the boat could operate for at ; when surfaced, she could travel at. U-181 was fitted with six torpedo tubes, 24 torpedoes, one SK C/32 naval gun, 150 rounds, and a SK C/30 with 2575 rounds as well as two C/30 anti-aircraft guns with 8100 rounds. The boat had a complement of fifty-five.
Operational history
Under Lüth's command she sailed on two long combat patrols in late 1942 and 1943, patrolling the waters off South Africa and Mozambique and sinking 22 ships for a total of 103,712 tons, making Lüth the second most successful U-boat commander of the war and earning him promotion to Korvettenkapitän and the Knight's Cross of the Iron Cross with Oak Leaves, Swords and Diamonds. He went on to command the 22nd U-boat Flotilla. On 1 November 1943 under the command of Fregattenkapitän Kurt Freiwald and part of the 12th U-boat Flotilla. U-181 sailed from her base in Bordeaux, France to Penang, Malaya in mid–1944, sinking four ships totalling 24,869 tons. They carried a Bachstelze and a Naxos radar detector on this trip. On 1 October 1944 the U-boat was transferred to the 33rd U-boat Flotilla. She carried out only one additional patrol in the Indian Ocean, in 1944–1945, on their journey home with 130 tons of tin, 20 tons of molybdenum, 80-100 tons of raw rubber, and the latest radar-detection equipment FUMB26 TUNIS. They ended up sinking a single ship of 10,198 tons. Because of their cargo, they only had room for two torpedoes, which they used in this sinking. The trip home was aborted when the main bearings started to wear out, prompting a return to Batavia on 6 January 1945, but transferring their fuel to near the Cocos Islands on the way. On the 12th, they were ordered to Penang, but only made it as far as Singapore. There they worked on repairing the engines and fitting a Schnorchel, before attempting a renewed trip home starting on 10 May.
On 6 May, Otto Giese dropped the two code-key machines into the Singapore harbor, and later that day, the boat was "taken" by the Japanese Captain Marujama. Admiral Paul Wenneker sent the message on 8 May, that Lubeck was in place, "an early agreement between Germany and Japan, if one nation lost and the other continued fighting, the former would render its war material to the latter." The crew was taken to Batu Pahat. After Germany's surrender in May 1945 the U-boat was taken over by Japan at Singapore and commissioned as I-501 on 15 July 1945. She surrendered to Allied forces there in August 1945, and was sunk on 12 February 1946 in the Strait of Malacca, in position, by the British frigates and.
