German submarine U-175 was a Type IXC U-boat of Nazi Germany's Kriegsmarine built for service during World War II.

Throughout her career, the boat undertook three war patrols during which she sank ten merchant ships amounting to a total of 40,619 gross register tons (GRT) before being sunk by the US Coast Guard cutter Spencer on 17 April 1943.

[4] The vessel's keel was laid down in the DeSchiMAG AG Weser shipyard in Bremen on 30 January 1941 at which point it became known by the yard number or designation 1015.

[2] Built alongside U-174 and U-176, the boat's crew was slowly assembled during construction, they were billeted within a building at the North German Lloyd Shipping Company, also in Bremen.

[2] Bruns graduated from the 1931 class and had previously commanded a torpedo boat, T3, which had been sunk by British aircraft in September 1940 near Le Havre.

[10][11] British naval intelligence, which tried to maintain personality and psychological profiles on all U-boat commanders, assessed him as "too ambitious and incautious".

[12] Nevertheless, he was later described by his crew as a "'humane officer' with more concern for...his men than the niceties of military protocol" who was "strict, but fair" and "dedicated to running an efficient, contented boat".

Tasked with carrying out operations in the Windward Passage in the Caribbean Sea, Bruns took his boat into the North Atlantic between the Faroe Islands and Iceland and, after crash-diving to avoid an Allied aircraft, set sail towards Barbados.

[17] Shortly before their arrival, on 11 September, Bruns received orders from BdU to relocate his boat to the mouth of the Orinoco River and to carry out his patrols.

[18] The haphazard defensive measures that had characterized the Allied convoy protection efforts in the region – and which had been taken advantage of so effectively during the early stages of Operation Neuland[19] – had been rectified to some extent by the time U-175 arrived in the Caribbean.

A brief period of panic was experienced by the crew when one of the lookouts mistook four porpoises for torpedoes and sounded an alarm, before realizing his mistake.

Bruns ordered a crash dive and resurfaced shortly afterwards, only to be harassed a number of times during the night by aircraft which began dropping depth charges at around 01:00 on 2 December.

[27][28] The boat then proceeded to its patrol area off the coast of Freetown, Sierra Leone, traversing a track between Grand Canaria and Fuerteventura in the Canary Islands.

[27] By 11 December, without having encountered any Allied ships, the crew had managed to repair the exhaust valves and after reporting this to BdU, Bruns received orders to proceed to the Cape Verde Islands, where no U-boat had previously been sent.

[29] For the next month, U-175 patrolled the waters off the west coast of Africa as BdU attempted to move them into position to attack ships in the area.

After questioning the crew in their lifeboats and pointing them in the direction of the nearest land, Bruns delivered the final blow to the Benjamin Smith by firing another torpedo which exploded amidships on the port side and sent the ship to the bottom.

Finally, late on 30 January, they resurfaced and made some hasty repairs which included rewiring the propellers so that they would both run off the starboard diesel engine; the port power plant had been badly damaged.

Upon their return to Lorient, which by that time had been heavily bombed by the Allies, the boat underwent repairs, first on its periscope and then the damaged port diesel and the electric motors.

[37] Departing Lorient with an armed escort known as a Sperrbrecher and three anti-submarine vessels, U-175 proceeded independently after passing Ile de Groix.

[42] As she came back, she attempted to pass ahead of the convoy to take up her station, and in doing so found U-175 where she was sitting at periscope depth preparing to launch a submerged attack upon the G Harrison Smith, a tanker of 11,752 GRT.

[44] This second attack ruptured U-175's pressure hull, destroyed the electric motors and damaged several batteries which, as a result, began to give off poisonous gas.

The Coast Guard crewmen, however, did not immediately understand the Germans' intentions and maintained a devastating fire on the conning tower that cut down Bruns and a number other men and forced the others to delay their exit.

[46] As the remaining Germans began to jump into the sea, the Spencer's boarding party attempted to get into the U-boat to search for documents and survivors.

[47] Of the 54 men that had embarked in U-175, 13 were killed, 19 were rescued by Spencer and 22 were picked up by Duane,[47] where they were formally taken prisoner, treated for their wounds and provided with dry clothing and warm food.

A number of other boats, including U-382, U-226 and U-264 were badly damaged in the ensuing engagement and the Allies later reinforced the escort around convoy HX 233 and increased the air assets assigned to it.

[2] U-175 took part in one wolfpack, namely: U-175 conducted three patrols and sank 10 merchant ships for a total of 40,619 gross register tons (GRT):[49]