German submarine U-175

German submarine U-175 was a Type IXC U-boat of the Nazi German Kriegsmarine built for service during World War II. She was laid down on 30 January 1941 at Bremen, and commissioned on 5 December 1941 with Kapitänleutnant Heinrich Bruns in command. After training with the 4th U-boat Flotilla, U-175 was transferred to the 10th U-boat Flotilla for front-line service. Throughout her career, the boat undertook three war patrols during which she sank 10 merchant ships amounting to a total of before being sunk by the US Coast Guard cutter USCGC Spencer on 17 April 1943.

Construction
U-175 was ordered by the Kriegsmarine on 23 December 1939. She was constructed as part of Plan Z, a naval construction program that envisaged the acquisition of 249 U-boats along with numerous surface vessels by 1948, and which was in direct contravention of Germany's obligations under the Anglo-German Naval Agreement. The vessel's keel was laid down in the AG Weser shipyard in Bremen on 30 January 1941 at which point it became known by the yard number or designation Werk 1015. 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. After about nine months of construction U-175 was launched on 2 September 1941.

Design
U-175 was a type IXC long-range attack submarine, one of 54 built. Like the other vessels of her type, U-175 displaced 1120 LT while surfaced and 1232 LT when submerged. She was 76.8 m in length overall and had a 4.4 m pressure hull. She had a height of 9.4 m and a draft of 4.7 m.

As part of the improvements of the IXC type over the previous IXBs, U-175 was able to carry an extra 43 tonnes of fuel, giving her a capacity of 208 tonnes. Her propulsion system consisted of two MAN 9-cylinder M9V40/46 supercharged diesel engines that provided a total of 4400 bhp, giving a maximum speed of 18.3 kn on the surface and a range of 13450 km at 10 kn. This power plant was heavier than those in previous models, and in order to accommodate this and balance the boat, the engine room was built directly aft of the control room, as opposed to behind the galley like in other types. The periscope in the control room was also deleted, leaving the boat with just two of the optical devices, both of which were located in the conning tower.

The submarine was also equipped with two Schichau Seebeckwerft GU345/34 double-acting electric motors which provided 1000 shp. They could propel U-175 63 km at 4 kn when submerged, with an underwater maximum of 7.3 kn. The U-boat's crush depth was rated at 200 m. U-175's armament consisted of six 21 in torpedo tubes; four of these were positioned in the bow, two were in the stern. She could carry 22 torpedoes, or when fitted as a minelayer could carry 44 TMA mines or 66 of the TMB variant. U-175 was also equipped with one 10.5 cm SK L/45 deck gun, for which 110 rounds were carried. In addition to this, for anti-aircraft defense, the boat was provided with two guns: one 2 cm C30 variant and one 3.7 cm Flak 43 M43U. Both weapons were located aft of the conning tower and trained rearward. U-175 had a crew of between 48 and 56.

Working up
U-175 was commissioned into the Kriegsmarine on 5 December 1941  under the command of Korvettenkapitän Heinrich Bruns. Bruns graduated from the 1931 class and had previously commanded a torpedo boat, T-3, which had been sunk by British aircraft in September 1940 near Le Havre. After recovering from his wounds, Bruns served on a training ship before transferring to the U-boat service in early 1941. Upon completion of the U-boat captain's course, Bruns served briefly on U-75, where he was confirmed as suitable for command. He was 29 years old upon taking up his post with U-175. Although British naval intelligence, which tried to maintain personality and psychological profiles on all U-boat commanders, assessed him as "too ambitious and incautious". 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".

Between 23 December 1941 and 6 January 1942, the boat was assigned to the 4th U-boat Flotilla where she carried out acceptance trials, doing so alongside four other boats commissioned around the same time. These were successfully completed and the boat was officially accepted. She was then sent to Gdynia to undertake torpedo exercises. Freezing temperatures, however, kept her there until late April. As they were ice-bound, the exercises were canceled; as such, the boat offloaded its crew to a depot ship, Frida Horn. They were finally able to complete their two week-long exercises in May off the coast of Hela in Poland. The following month she took part in tactical exercises, during which time one of her periscopes was damaged when she surfaced below a cutter. The result of this was that she was forced to put into Danzig for repairs before carrying out "silent-running tests" near Bornholm. These tests delivered bad news for U-175's crew as the boat proved to be "exceptionally noisy".

Throughout June and July, U-175 conducted a six-week "shake-down" at Stettin along with U-512 and U-181. During this time, the crew was based at Bredower Naval Barracks. With the working-up completed, the boat was fuelled and took on board a consignment of 15 electric and eight air-cooled torpedoes before departing for Kiel on 27 July. Around this time the boat was re-assigned to Gunther Kuhnke's 10th U-boat Flotilla for front-line service, although this only became official on 1 September.

First patrol: Trinidad
On 10 August 1942, under orders from the U-boat high command, Befehlshaber der U-Boote (BdU), U-175 departed Kiel along with a small escort and another U-boat - U-179. The two boats proceeded to an advanced base in Norway where they refueled two days later before continuing on their way to their operational assignments separately. Tasked with carrying out operations in the Windward Passage in the Caribbean Sea, Brun 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. 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. After briefly patrolling around Bridgetown, where another U-boat had reported sinking two tankers earlier, U-175 took up station in its assigned area.

By this stage, 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, had been rectified to some extent by the time U-175 arrived in the Caribbean. Nevertheless, the boat's first patrol in the area was a huge success. One of five Type IXs that were sent to the region, out of a total of 30 vessels that were sunk at this time, Bruns' boat accounted for nine, amounting to 33,442 GRT. The first of these came on 18 September when, after having hit but failed to sink the Norwegian freighter Sorvangen, U-175 sank the Norfolk, a Canadian freighter belonging to the Canada SS Line. Four American ships followed this, along with one Panamanian, a Yugoslavian and a British ship, with the final one, the William A. McKenney, being sunk on 5 October. Finally, on 7 October, having fired all of her torpedoes, U-175 received orders to end her patrol and make for the U-boat base at Lorient, in German occupied France; crossing the Atlantic via the Little Antilles and the Azores, they arrived there on 27 October. During the patrol, the boat had largely been unmolested by Allied aircraft, except for two attacks which occurred on 2 October, when she was bombed by a Martin PBM Mariner, but suffered only "light damage".

Second patrol: West Africa
Following the boat's arrival at Lorient, the crew received three weeks leave. In order to maintain a skeleton crew remaining behind, this was taken in shifts. During this time, the boat was in the dry dock within the Scorff Shelter submarine pen. She stayed there for two days while her equipment was tested before being transferred to the Keroman shelter where the more extensive work was undertaken. This involved the removal and replacement of one of the periscopes, rebuilding the compressors and overhauling the electric motors. At this time, the boat also received a Metox radar detector. By the end of November, the boat conducted short sea trials and was declared ready to undertake its next patrol.

This began on 1 December 1942, when late in the afternoon the boat, in concert with a type VIIC boat from Brest, was escorted out of Lorient towards the Isle de Groix, a brief period of panic was experienced by the crew when one of the lookouts mistook four porpoises as torpedoes and sounded an alarm before realizing his mistake. A short time later, however, the boat was forced to submerge when the radar detector warned of an incoming Allied aircraft. Bruns ordered a crash dive, but shortly afterwards resurfaced only to be harassed a number of times again during the night by aircraft that began dropping depth charges at around 01:00 on 2 December, but these were aimed at the type VIIC boat that was traveling with U-175's.

As they traversed the Bay of Biscay, U-175 was forced to crash dive on a number of occasions as Allied aircraft approached; during this time the boat was plagued by an almost constant leaking of sea water through its joints which required tightening. Two days later, on 4 December, after receiving a convoy sighting report from U-603 via BdU, Bruns decided to try to attempt an interception of the convoy which was believed to be east of Cape Finisterre, even though by this time the exhaust valves on the diesel engines were leaking. After being forced to crash-dive upon being surprised by an Allied seaplane, the leaks forced Bruns to surface and eventually break off the attempt to join the attack.

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. On 8 December they encountered a neutral Spanish tanker, the Zorroza, which Bruns allowed to continue on its way. 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. The submarine arrived there on 12 December before moving on to a point west of Dakar. 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. Staying underwater during the day, and sailing on the surface at night, they spotted a number of neutral vessels during this time, but left them alone. They were attacked once by an Allied aircraft on New Years Day; again very little damage was caused.

At 18:00 on 22 January 1943, U-175 spotted an unescorted American Liberty Ship, the Benjamin Smith. The first two torpedoes fired at the ship missed, Bruns decided that it was too dangerous to remain on the surface and decided to submerge in case Allied aircraft were about. After an hour, the boat surfaced and reacquired the target, then some 9 mi away and pursued it for eight hours. Early on 23 January U-175 scored a hit on the American vessel with the first torpedo fired, however, it continued sailing, so Bruns ordered another torpedo to be fired. This one missed, but a third struck below the mainmast and forced the crew to abandon ship. 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.

Bruns then took his boat north to make a rendezvous with a Milchkuh replenishment vessel to complete refueling. However, while traveling on the surface they were surprised by a Catalina aircraft and only just managed to dive in time to avoid the depth charges that were dropped. On 30 January, after British intelligence learned of the rendezvous, U-175 was subjected to a heavy air attack which resulted in extensive damage and for a time the U-boat was diving out of control by the stern to a depth of 310 m, which was well beyond the hull's tested crush depth. An emergency release of ballast retrieved the situation, but resulted in the boat angling up abnormally out of the water. Upon coming to the surface, the boat was subjected to machine-gun fire which forced them to dive once more. 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. The U-boat was then able to gingerly continue on its way. The attack had also breached one of the boat's fuel tanks and, as a result of a leak, the crew were forced to arrange an emergency resupply. This occurred on 15 February when U-175' rendezvoused with U-118, from whom she received about 30 tons of fuel as well spare parts for the radar system and fresh food. Following this Bruns set off directly for Lorient; moving on the surface at night, they arrived on 24 February 1943. They had been at sea for 86 days.

Third patrol: Atlantic
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. In addition to this new batteries were installed and the compressor was given a tune-up. Meanwhile, the crew were housed in air raid shelters rather than a barracks, as all the other accommodation had been destroyed. A number of crew members were sent away on promotion or training courses and in their place new personnel arrived. As a result, the crew composition changed considerably; the average age on board by the time of the third patrol was 23.



The boat's repairs took longer than expected and instead of being completed by 4 April, it was not until the 10th that the boat was ready to depart on its third patrol. Nevertheless, when she left, she did so with repairs incomplete and a number of dock workers remained on board to finish these off while at sea. Departing Lorient with an armed escort known as a Sperrbrecher and three anti-submarine vessels, U-175 proceeded independently after passing Ile de Groix. In the days that followed, a number of radar contacts sent the boat below the surface. However, by 15 April they had arrived in the Mid-Atlantic air gap where they were out of range of Allied aircraft, allowing them to operate on the surface with less circumspection. The following day, BdU ordered U-175 to join an attack on convoy HX-233, a Liverpool-bound convoy which had departed Halifax and New York earlier in the month, which had been spotted by U-262 while on a clandestine operation to pick up German prisoners-of-war. Steaming at full speed, the boat beat towards the convoy for 10 hours before finally spotting it just before midnight on 16 April. At this point Bruns reported the sighting to BdU, who relayed it to two other boats, U-382 and U-628, while Bruns attempted to get in front of the convoy to set up an attack. Four other boats – U-226, U-264, U-358 and U-614 – also subsequently converged on the convoy.

In the early morning of 17 April, U-628 torpedoed one of the freighters in the convoy, Fort Rampart. A short time later, one of the convoy's escorts, the United States Coast Guard cutter USCGC Spencer, under Commander Harold Berdine, responding to a signal from one of the other escorts, the corvette HMCS Arvida, moved away from the convoy to screen the cutter while it picked up survivors. Once this was completed, she steamed back towards the convoy. 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. Picking up a contact on her sonar about 5000 yd, she rushed ahead at full speed. The sound of the sonar pinging on the boat alerted Bruns to the danger and he gave the order for the boat to dive. However, Spencer launched a salvo of 11 depth charges which exploded above and below the boat. The result was that the boat went into a dive bow first and just as they began to restore buoyancy, Spencer launched a second salvo. 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.



At this point Spencer attacked again and was joined by another Coast Guard cutter, the USCGC Duane, they waited for U-175 to surface. On board U-175, quick thinking by the boat's engineer to blow the ballast tanks had prevented them from sinking further and helped right the boat, but communications had been knocked out and it became clear to Bruns that the only option was to surface. Giving the order, the boat rose to the surface; as it did so, Spencer and Duane began firing at close range, while Spencer's commander, Berdine, closed with intent to ram. But Bruns was not intending to fight it out and, seeking to save his crew, led the way onto the conning tower to signal his intention to surrender. 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. During the firing, stray rounds from one of the merchant ships hit Spencer killing one and wounding seven others.

At this point, Beredine, believing U-175 to still be in the fight, put Spencer about to ram the U-boat but the escort commander, Commander Paul Heineman, ordered him to "heave to" and put a boarding party across instead. 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. The boat quickly began to go under, though, and as a result they were forced to make a hasty departure without having found anything. 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, where they were formally taken prisoner, treated for their wounds and provided with dry clothing and warm food. Meanwhile, the battle for the convoy continued. A number of other boats, including U-382, U-226 and U-264 were badly damaged in the ensuing engagement and the Allies would later reinforce the escort around convoy HX-233 and increase the air assets assigned to it. In response, on 18 April, BdU canceled operations against the convoy, which subsequently arrived in Liverpool on 21 April, having lost only one of its 57 ships.

U-175's final resting place is recorded as south-west of Ireland, at position 47.88333°N, -22.06667°W.

Ships sunk
U-175 conducted three patrols and sank 10 merchant ships for a total of :