SM U - 5 ( Austria - Hungary ) SM " U - 5 or U - V " was the lead boat of the " U - 5 " class of submarine s or U - boat s built for and operated by the Austro - Hungarian Navy ( ) before and during the First World War . The submarine was built as part of a plan to evaluate foreign submarine designs , and was the first of three boats of the class built by Whitehead & Co . of Fiume after a design by American John Philip Holland . " U - 5 " was laid down in April 1907 and launched in February 1909 . The double - hull ed submarine was just over long and displaced between , depending on whether surfaced or submerged . " U - 5 " s design had inadequate ventilation and exhaust from her twin gasoline engines often intoxicated the crew . The boat was commissioned into the Austro - Hungarian Navy in April 1910 , and served as a training boat — sometimes making as many as ten cruises a month — through the beginning of the First World War in 1914 . The submarine scored most of her wartime successes during the first year of the war while under the command of Georg Ritter von Trapp . The French armoured cruiser " Léon Gambetta " , sunk in April 1915 , was the largest ship sunk by " U - 5 " . In May 1917 , " U - 5 " hit a mine and sank with the loss of six men . She was raised , rebuilt , and recommissioned , but sank no more ships . At the end of the war , " U - 5 " was ceded to Italy as a war reparation , and scrapped in 1920 . In all , " U - 5 " sank four ships totaling . Design and construction . " U - 5 " was built as part of a plan by the Austro - Hungarian Navy to competitively evaluate foreign submarine designs from Simon Lake , Germaniawerft , and John Philip Holland . The Austro - Hungarian Navy authorized the construction of " U - 5 " ( and sister ship , " U - 6 " ) in 1906 by Whitehead & Co . of Fiume . The boat was designed by American John Philip Holland and licensed by Holland and his company , Electric Boat . " U - 5 " was laid down on 9 April 1907 in the United States , partially assembled , and shipped to Whitehead ' s for final assembly , a process which , author Edwin Sieche notes , " caused a lot of trouble " . She was launched at Fiume on 10 February 1909 by Agathe Whitehead , and towed to Pola on 17 August . " U - 5 " s design featured a single - hull with a teardrop - shaped body that bore a strong resemblance to modern nuclear submarines . She was long by abeam and had a draft of . She displaced surfaced , and submerged . Her two bow torpedo tubes featured unique , cloverleaf - shaped design hatch es that rotated on a central axis , and the boat was designed to carry up to four torpedoes . For surface running , " U - 5 " was outfitted with 2 gasoline engines , but suffered from inadequate ventilation , which resulted in frequent intoxication of the crew ; her underwater propulsion was by two electric motors . Service career . " U - 5 " was commissioned into the Austro - Hungarian Navy on 1 April 1910 , with " Linienschiffsleutnant " Urban Passerar in command . Over the next three years she served primarily as a training boat , making as many as ten training cruises per month . On 1 May 1911 , she hosted a delegation of Peruvian Navy officers that inspected her . In June 1912 , she towed a balloon as part of efforts to assess the underwater visibility of hull paint schemes . At the outbreak of World War I , " U - 5 " was one of only four fully operational U - boats in the Austro - Hungarian Navy fleet . She was initially stationed at the submarine base on Brioni , but was moved to Cattaro by late 1914 . " U - 5 " made an unsuccessful attack on a French battleship squadron off Punta Stilo on 3 November . In December , the ship ' s armament was augmented by a 3 . 7 cm / 23 ( 1 . 5 in ) quick - firing ( QF ) deck gun , and had her first radio receiver installed . In April 1915 , Georg Ritter von Trapp assumed command of " U - 5 " , and the following month , led the boat in sinking the French armored cruiser off Santa Maria di Leuca . On the night of 26 April , " Léon Gambetta " was patrolling the Straits of Otranto at a leisurely without the benefit of a destroyer screen . " U - 5 " launched two torpedoes at the French cruiser , hitting with both . The ship was rocked by the explosions of the two torpedoes and went down in ten minutes , taking down with her the entire complement of officers , including Rear Admiral Victor Baptistin Sénès . Of the French ship ' s complement , 648 were killed in the attack ; there were 137 survivors . " Léon Gambetta " was the largest ship of any kind sunk by " U - 5 " . Victims Gallery . In June , " U - 5 " helped search for the lost Austro - Hungarian seaplane " L 41 " , and in July , received an upgrade of her deck gun to a QF gun . In early August , " U - 5 " was sent out from Lissa when the Austro - Hungarian Navy received word from a reconnaissance aircraft that an Italian submarine had been sighted at Pelagosa . On the morning of 5 August , the Italian submarine " Nereide " was on the surface , moored under a cliff in the island ' s harbor . When " U - 5 " surfaced just offshore , " Nereide " s commanding officer , " Capitano di Corvetta " Carlo del Greco , cast off the lines and maneuvered to get a shot at von Trapp ' s boat . " Nereide " launched a single torpedo at " U - 5 " that missed , after which del Greco ordered his boat submerged . " U - 5 " lined up a shot and launched a single torpedo at the slowly submerging target , striking her , and sending her to the bottom with all hands . The Italian captain received the " Medaglia d ' Oro al Valore Militare " for his actions . At the end of August , " U - 5 " captured the Greek steamer " Cefalonia " as a prize off Durazzo . In late November , Friedrich Schlosser succeeded von Trapp as " U - 5 " s commanding officer . Schlosser and " U - 5 " made an unsuccessful attack on an Italian on 7 June 1916 , but the boat managed to torpedo the Italian armed merchant cruiser off Cape Linguetta on the next day . According to a contemporary account , " Principe Umberto " and two other ships were transporting troops and materiel under escort of two destroyers . After the torpedo hit , " Principe Umberto " went down quickly with the loss 1 , 750 men . " Principe Umberto " was the last ship hit by " U - 5 " . Gallery . On 16 May 1917 , " U - 5 " was conducting a training cruise in the Fasana Channel near Pula when her stern struck a mine . The boat sank at a depth of with a loss of 6 of the 19 men on board . From 20 to 24 May the submarine was raised , and through November underwent a refit . During this reconditioning , a new conning tower was added and the deck gun was upgraded again , this time to a 7 . 5 cm / 30 ( 3 . 0 in ) gun . Upon completion , " U - 5 " was recommissioned , but had no more war successes . In her career , " U - 5 " sank a total of four ships totaling . After the war ' s end , " U - 5 " was transferred to Venice where she was inspected by British military commissions . " U - 5 " was later ceded to Italy as a war reparation in 1920 and was scrapped .