German submarine U - 99 ( 1940 ) German submarine " U - 99 " was a Type VIIB U - boat of the German Navy ( " Kriegsmarine " ) during World War II . She was laid down on 31 March 1939 at the Friedrich Krupp Germaniawerft in Kiel as ' werk ' 593 . She was launched on 12 March 1940 under the command of Korvettenkapitän Otto Kretschmer and was assigned to the 7th U - boat Flotilla based in Kiel and later in St Nazaire . " U - 99 " was one of the most successful German U - boats in the war , sinking 38 ships for a total tonnage of of Allied shipping in eight patrols . She damaged five more ships and took one vessel as a prize . Career . From April to June 1940 , the crew of " U - 99 " were under training , based at Kiel and St . Nazaire . 1st patrol . On 18 June , " U - 99 " departed Kiel for operations in the North Sea west of Norway . She was attacked by an Arado Ar - 96 seaplane from the German battleship , having been mistaken for a British submarine . Two days later , " U - 99 " was attacked by two aircraft ; minor damage was inflicted . She returned to Kiel on 25 June . 2nd patrol . " U - 99 " departed Wilhelmshaven on 27 June to patrol southwest of Ireland . On 29 June , she was attacked by British aircraft . A crash dive was carried out with the result that the boat hit the seabed , causing some damage which was able to be repaired . During this patrol , " U - 99 " sank six ships . A seventh was captured . An attack on the 5 , 360 GRT was called off on 7 July , when the armed merchant ship fired upon the U - boat . On 8 July , over 100 depth charge s were dropped by the escorts of Convoy HX 53 , but " U - 99 " escaped undamaged . The patrol ended on 21 July . 3rd patrol . On 25 July , " U - 99 " departed Lorient for the North Atlantic . Four ships were sunk and three others damaged . On the 31st , the escorts of Convoy OB 191 dropped 20 depth charges on the boat without effect . Later that evening , a flying boat also attacked her , again without causing any damage . The patrol ended on 5 August . 4th patrol . " U - 99 " departed Lorient on 4 September for the North Atlantic ; seven ships were sunk . The patrol ended on the 25th . " U - 99 " was slightly damaged in an air raid on Lorient on 27 September . 5th patrol . On 13 October , " U - 99 " departed Lorient to patrol the North West Approaches . Six ships from Convoy SC 7 were sunk and another was damaged . The patrol ended on 22 October . 6th patrol . " U - 99 " departed Lorient for the North West Approaches on 30 October 1940 ; four ships were sunk . The patrol ended on 8 November . 7th patrol . On 27 November , " U - 99 " departed Lorient for the North Atlantic . Four ships were sunk . The patrol ended on 12 December . 8th patrol . " U - 99 " departed Lorient on 22 February 1941 to patrol in the North Atlantic ; eight ships were sunk . " U - 99 " was attacked herself , with severe damage inflicted . Kretschmer surrendered and scuttled the submarine with the loss of three lives . Fate . On 17 March 1941 , " U - 99 " had just fired the last of her torpedo es and sunk " Korshamn " when the Watch Officer spotted a destroyer , south - east of Iceland in approximate position . He immediately ordered a dive , contrary to Kretschmer ' s standing orders , but once the boat was under it was quickly fixed on ASDIC and attacked by HMS " Walker " and " Vanoc " . " U - 99 " was driven deep by the attack but was nonetheless severely damaged . Kretschmer had no choice but to surface ; immediately a barrage of fire greeted the boat . Kretschmer sent a message to Donald Macintyre , " Walker " s captain , " CAPTAIN TO CAPTAIN . I AM SUNKING [ sic ] PLEASE RESCUE MY CREW . " He then ordered that the boat should be scuttled . 40 crew , including Kretschmer , were rescued to become POWs , while three crewmen lost their lives . Macintyre took Kretschmer ' s binoculars as a souvenir . Wolfpack operations . " U - 99 " operated with the following Wolfpacks during her career :