German submarine U - 28 ( 1936 ) German submarine " U - 28 " was a Type VIIA U - boat of the Nazi German " Kriegsmarine " during World War II . Her keel was laid down on 2 December 1935 , by AG Weser of Bremen . She was launched on 14 July 1936 , and commissioned into the " Kriegsmarine " on 12 September 1936 , with " Kapitänleutnant " Wilhelm Ambrosius in command . Ambrosius was succeeded by nine other commanding officers over the next eight years . " U - 28 " conducted seven war patrols between 19 August 1939 and 15 November 1940 , all under the command of " Kapitänleutnant " Günter Kuhnke , sinking 13 ships totaling and damaging two others totaling . After her third patrol , " U - 28 " became a training vessel and was used to bring new U - boat crews up to standard . She was later sunk in an accident on 17 March 1944 and stricken on 4 August 1944 . Construction and design . Construction . " U - 28 " was ordered by the German " Kriegsmarine " on 1 April 1935 as part of the German Plan Z and in violation of the Treaty of Versailles . Her keel was laid down in the AG Weser shipyard in Bremen as " Werk " 909 on 2 December 1935 . After about ten months of construction , she was launched on 14 July 1936 and commissioned into the " Kriegsmarine " as the third Type VIIA submarine on 12 September 1936 under the command of " Kapitänleutnant " Wilhelm Ambrosius . Design . Like all Type VIIA submarines , " U - 28 " displaced while surfaced and when submerged . She was in overall length and had a pressure hull . " U - 28 " s propulsion consisted of two MAN 6 - cylinder 4 - stroke M6V 40 / 46 diesel engines that totaled . Her maximum rpm was between 470 and 485 . The submarine was also equipped with two Brown , Boveri & Cie GG UB 720 / 8 electric motors that totaled . Their maximum rpm was 322 . These power plants gave " U - 28 " a maximum speed of while surfaced and when submerged . She had a range of while traveling at on the surface and at when submerged . The U - boat ' s test depth was but she could go as deep as without having her hull crushed . " U - 28 " s armament consisted of five torpedo tube s , ( four located in the bow and one in the stern ) . She could have up to 11 torpedoes on board or 22 TMA mines or 33 TMB mines . " U - 28 " was also equipped with a C35 88 mm gun / L45 deck gun with 220 rounds . Her anti - aircraft defenses consisted of one C30 20 mm AA gun . Service history . First patrol . " U - 28 " s first war patrol took place from 19 August to 29 September 1939 . On 14 September , while sailing around the mouth of St George ' s Channel , " U - 28 " sank a 5 , 000 ton freighter , which was her only success of the patrol . Second patrol . " U - 28 " s second war patrol took place from 8 November to 12 December 1939 . For this effort she was instructed to lay a minefield near the port city of Swansea . En route to Bristol , " U - 28 " sank two ships ; the 5 , 000 ton Dutch tanker MV " Sliedrecht " and the 5 , 100 ton British freighter SS " Royston Grange " . " U - 28 " then laid her minefield and returned to port in Germany . While the minefield was not an immediate success , it sank the 9 , 600 ton British freighter SS " Protesilaus " 60 days after it was laid . Third patrol . " U - 28 " s third sortie took place from 18 February to 25 March 1940 . She was instructed to lay mines off the British Naval Base at Portsmouth . After " U - 28 " laid the minefield , she went on to sink two ships for 11 , 200 tons . Fourth patrol . " U - 28 " s fourth war patrol took place from 8 June to 7 July 1940 . She was sent to the Western Approaches and turned in an average performance of sinking three ships totalling 10 , 300 tons . The Irish government sought an explanation from Germany for the sinking of the neutral Greek ship " Adamandios Georgandis " : " the entire cargo of which comprised grain for exclusive consumption in Éire " She was sailing from Rosario ( in Argentina ) to Cork with a cargo of wheat when she was torpedoed and sunk south - west of Ireland at . Fifth patrol . " U - 28 " s fifth war patrol took place from 11 August to 17 September 1940 and was one of Kuhnke ' s most productive . In August , she sank two ships for 5 , 500 tons . On 10 September , " U - 28 " found and tracked Convoy OA 210 . In the darkness of early morning on 11 September , " U - 28 " attacked the convoy and claimed two large freighters ( 13 , 000 tons each ) sunk and caused damage to a 10 , 000 ton tanker , bringing Kuhnke ' s total for the patrol to five ships for 30 , 000 tons . However , during the postwar analysis , he was only credited with sinking a 2 , 000 ton Dutch freighter and damaging a 4 , 700 ton British freighter ; which , combined with his earlier sinkings , brought his total to four ships for 9 , 945 tons . On his return to Lorient Kuhnke was awarded the Knight ' s Cross for his work . Sixth patrol . " U - 28 " s sixth and final war patrol took her from Lorient back to Germany ; because of the heavy seas and foul weather , " U - 28 " sank only half a ship for 2 , 694 tons . ( " U - 28 " and shared credit for the sinking of the SS " Matina " ) . On 15 November 1940 , she returned to Germany and was turned over to the training command . Günter Kuhnke proceeded to command . Fate . " U - 28 " sank by accident on 17 March 1944 , at the U - boat pier in Neustadt . During a training exercise , the boat had passed under a dummy freighter used for target practice . The commander - in - training failed to note the position of the stationary freighter , and the U - boat ' s conning tower was ripped off . Water flooded the control room , but the other compartments remained intact . The crew escaped by slowly equalizing the water pressure in the boat and swimming to the surface . The boat was raised in March 1944 , but was stricken on 4 August . The submarine ' s crew suffered no casualties during her career .