German submarine U - 176 German submarine " U - 176 " was a Type IXC U - boat in the Nazi German " Kriegsmarine " during World War II . Built at the AG Weser shipyard in Bremen , she was laid down on 6 February 1941 , launched on 12 September and commissioned on 15 December , under the command of " Kapitänleutnant " Reiner Dierksen . " U - 176 " served with the " 4 . Unterseebootsflotille " ( U - boat flotilla ) while training , and from 1 August 1942 with the " 10th U - boat Flotilla " , a long - range operations unit . " U - 176 " completed three patrols , sinking 11 ships totalling before she was sunk off Cayo Blanquizal by the Cuban navy on 15 May 1943 . Service record . 1st patrol . On 21 July 1942 " U - 176 " sailed from Kiel , around the British Isles , and into the north Atlantic Ocean . She made her first kill on 4 August , sinking the unescorted 7 , 798 ton British merchantman " Richmond Castle " with two torpedoes . On 7 August she joined five other U - boats in reinforcing the eight boats of wolfpack " Steinbrinck " in a series of attacks on Convoy SC 94 . On 8 August " U - 176 " fired two salvo es of two torpedoes each at the convoy , sinking two British cargo ships , the 4 , 817 ton " Trehata " and the 3 , 956 ton " Kelso " , and the 7 , 914 ton Greek cargo ship " Mount Kassion " . The next day she also sank another British ship , the 3 , 701 ton " Radchurch " , which had been abandoned . The convoy escort was then reinforced by the Polish destroyer and the British destroyer leader . Both ships were equipped with HF / DF ( radio direction - finding equipment ) , which helped to keep the U - boats at bay until morning . " U - 176 " sank the 7 , 457 ton British cargo ship with two torpedoes on 25 August . The ship had been part of convoy ON 122 ; the U - boat ended the patrol after 74 days at sea at Lorient in France on 2 October 1942 . The day after her return her captain was awarded the Iron Cross 1st Class . 2nd patrol . " U - 176 " departed Lorient on 9 November 1942 and headed into the south Atlantic . On 27 November she sank the 5 , 922 ton Dutch merchant ship " Polydorus " after a 50 - hour pursuit , the longest recorded by any U - boat in the Second World War . Off Cape Sao Roque , Brazil , on 13 December 1942 the crew of " U - 176 " boarded the 1 , 629 ton Swedish cargo ship " Scania " , and sank her with scuttling charges after the crew had abandoned ship . On 16 December she sank the unescorted 5 , 881 ton British cargo ship " Observer " with two torpedoes . < br > Prior to the sinking of the " Scania " , a young seaman , Gottfrid Sundberg , surreptitiously photographed " U - 176 " from the " Scania " . " U - 176 " arrived back at Lorient on 18 February 1943 after a patrol lasting 102 days . 3rd patrol . " U - 176 " sailed for her third and final patrol on 6 April 1943 from Lorient , sailing across the Atlantic and into the Caribbean Sea . On 1 May , her commander was notified of his promotion to " Korvettenkapitän " . On 13 May 1943 , " U - 176 " attacked Convoy NC 18 only five miles off the northern coast of Cuba , sinking the 2 , 249 ton American tanker " Nickeliner " , which was loaded with 3 , 400 tons of ammonia water , and the 1 , 983 ton Cuban molasses tanker " Mambí " . Sinking . On 15 May , the Cuban merchant ship " Camagüey " , and the Honduran " Hanks " , both loaded with sugar , sailed from Sagua La Grande , bound for Havana , escorted by the Cuban submarine chaser s " CS - 11 " , " CS - 12 " , and " CS - 13 " . At 17 : 15 hours , a U . S . Navy Kingfisher aircraft from squadron VS - 62 operating from Cuba spotted " U - 176 " at and dropped a smoke float to mark her position about one and a half miles astern of the convoy . " CS - 13 " located the U - boat with her sonar , attacked with depth charge s and sank " U - 176 " . On 7 January 1944 KrvKpt . Reiner Dierksen was posthumously awarded the " Deutsches Kreuz " in Gold . " CS - 13 " was commanded by the Cuban Navy ' s " Alférez de Fragata " , Mario Ramirez Delgado commanding , the only Cuban national to sink a U - boat during World War II . In 1946 , Delgado , promoted to Lieutenant , was awarded the " Orden del Mérito Naval con Distintivo Rojo " ( Meritorious Naval Service Order with Red Badge ) . Rear Admiral Samuel E . Morison , official historian of the US Navy , recognized his success in his work " History of United States Naval Operations in World War II " , where he also praised the ability and efficiency of the Cuban seamen . Also present was Norberto Collado Abreu , who later found fame as the pilot of the " Granma " , the yacht which brought Fidel Castro back to Cuba to restart the Cuban Revolution .