German submarine U - 546 German submarine " U - 546 " was a Type IXC / 40 U - boat operated by the German " Kriegsmarine " during World War II . She was laid down at the Deutsche Werft in Hamburg as " Werk " 367 on 6 August 1942 , launched on 17 March 1943 and commissioned on 2 June 1943 under " Oberleutnant " Paul Just . < ref name = " http / / uboat . net / boats / u546htm " > : http / / uboat . net / boats / u546htm < / ref > The U - boat was a member of three wolf pack s . " U - 546 " was responsible for the last combat sinking of a United States Navy vessel in the Atlantic Theatre , during Operation " Teardrop " . On 24 April 1945 " U - 546 " sank the destroyer escort , but was in turn sunk by combined fire of five other USN destroyers . Her captain and most of her crew were rescued by US vessels , and taken to Argentia Naval Station . It was from this crew that the USN eventually learned that no V - 1 / 2 attacks from the U - boats were planned by the Kriegsmarine . Service history . She commenced her training on 2 June 1943 , making her first silent run at Sønderborg , she remained with the " 4th U - boat Flotilla " ( training ) at Stettin until 31 December 1943 . She completed her training with a voyage from Hela to Swinemünde to practice A . A . cannon fire . 1st patrol . The boat was reassigned to the 10th U - boat Flotilla for combat duties in the Atlantic on 1 January 1944 , departing Kiel on 22 January 1944 , with a three day stopover at Marviken in Norway . After forming up with the " Gruppe Igel 1 " ( Group Hedgehog ) north - west of Scotland on 3 February 1944 , " U - 546 " commenced a patrol in the North Atlantic with other boats to the west of Ireland on anti - convoy duties . At 1229 on 16 February " U - 546 " reported she had been attacked by a British Sunderland flying boat from No . 201 Squadron RAF , killing one crewman . On 20 February 1944 she was again attacked by an aircraft . On 17 April while returning to base in France , the U - boat was caught on the surface by a Leigh light - equipped Liberator of 53 Squadron in the Bay of Biscay , steaming south - east , ahead of convoy HX - 278 and was attacked with depth charge s , but shooting down the attacker with the 3 . 7 cm gun . She returned to Lorient for service and refit on 23 or 25 April 1944 . The crew was given leave while the boat was overhauled and the " Schnorchel " was fitted . 2nd patrol . Leaving her base again on 15 June 1944 for her second patrol to the African Gold Coast , she was detected by a USN anti - submarine patrol , which begun to hunt her . She soon had to abort her patrol and was ordered to return to Germany after the invasion of Normandy . On the 18 June 1944 " U - 546 " was attacked , again by a Sunderland , which was not equipped with radar . The boat then briefly returned to France on 22 June to replenish her cannon ammunition , sailing again on 25 June . On the 20 July 1944 she was detected by USN surface ships forming the escort for an escort carrier ; " U - 546 " fired a torpedo at the carrier , but missed and was subjected to three hours of depth charge attacks from the escort destroyers . She managed to escape this attack . " U - 546 " was then ordered to patrol a zone near Cape Verde where she operated for about four weeks , attacking a convoy with a spread of three torpedoes , but scoring no hits . During the second patrol due to fuel shortages the captain achieved significant fuel saving and extended the cruise to 150 days ( the boat ' s longest patrol ) , by floating submerged for days on water - layers with all engines stopped . The boat returned to base with 30 metric tons of fuel left . 3rd patrol . On 10 November 1944 " U - 546 " was reassigned to the 33rd U - boat Flotilla based at Flensburg , where she received a 14 - day overhaul , eventually departing Kristiansand in Norway , on 2 March 1945 . The boat proceeded to the eastern coast of North America on 10 March 1945 with six companions . In mid - April the group was ordered to commence operations individually . On 23 April the submarine was spotted surfacing north - west of the Azores by aircraft from as part of Operation " Teardrop " . The planes were looking for U - boats carrying V - 1 flying bomb s and V - 2 rockets , which intelligence suggested were going to be used to attack American cities . Depth charges were dropped just after the boat submerged , but failed to damage her hull . Sinking . On 24 April 1945 , " U - 546 " made contact with the destroyer escort and proceeded to attack , firing a stern torpedo . The destroyer turned into it and was hit , which tore the DE apart and sent her down with heavy loss of life . The U - boat was in turn pursued by other destroyer escorts ; ( LCDR H . C . Dufe ) , ( LCDR L . A . Myhre ) , ( LCDR V . E . Gex ) , ( CDR L . C . Mabley ) , ( LCDR W . W . Patrick ) , ( LCDR D . S . Knox ) , ( LCDR S . G . Rubinow , Jr . ) , and ( LCDR G . W . Casselman ) " Neunzer " and conducted a search while " Pillsbury " circled the area and " Flaherty " picked up survivors . " Flaherty " made contact in less than an hour and with " Pillsbury " proceeded to attack . The U - boat went to . Contact was lost from 1045 until 1201 when " Varian " , " Janssen " and " Hubbard " began another attack . " Neunzer " got into the fight after several attacks by the other DE ' s , delivering a creeping attack with " Varian " and " Hubbard " while " Chatelain " directed . Contact was lost once more at about 1600 , so " Chatelain " and " Neunzer " were ordered to return to the scouting line . The line was expanded , the ships began a sweep through the area , determined to prevent the submarine ' s escape . " Varian " made contact once more at 1731 and " Flaherty " was ordered to attack . She fired at 1810 . Four minutes later a small oil slick began coming to the surface . " Flaherty " made another Hedgehog attack at 1828 , and at 1838 the U - boat broke the surface . Every ship in the line within range began firing . At 1844 , after more than ten and a half hours of attacks , " U - 546 " rolled under and sank ( in position , south - south - east of Cape Farewell , Greenland ) . Her captain and most of her crew were rescued by US vessels , and taken to Argentia Naval Station . It was from this crew that the USN eventually learned that no V - 1 / 2 attacks from the U - boats were planned by the Kriegsmarine . Sensors . Radar . " U - 546 " was one of the few U - boats that was fitted with a FuMO 61 " Hohentwiel " Radar Transmitter . The apparatus aboard " U - 546 " was installed on the starboard side of the conning tower . Radar Detection . " U - 546 " was fixed with the FuMB - 26 " Tunis " antenna .