SMS Cap Trafalgar SMS " Cap Trafalgar ( also called Cape Trafalgar " ) was a glamorous German liner converted to an auxiliary cruiser during World War I . The ship holds the dubious distinction of being the first armed merchant cruiser to have been sunk by a ship of the same class , having been destroyed in a furious action in the South Atlantic in September 1914 soon after the start of the war . Early career . She was originally a large ocean liner built for passenger use at the AG Vulcan Shipyard on the Elbe River in Hamburg , Germany , for the " Hamburg - South America Line " . She was completed in October 1913 , with 18 , 710 GRT and named after the Spanish Cape Trafalgar , scene of the famous Battle of Trafalgar in 1805 . She spent the next year steaming between the German port of Hamburg and the ports of Brazil and Chile , where large numbers of German immigrants had settled . She was in commercial service when war was declared in Europe in August 1914 . World War I ; the Battle of Trindade . Conforming to pre - war plans , she was summoned to duty in the German Imperial Navy . All passengers and non - essential personnel were disembarked at Montevideo , Uruguay and then the ship set off to rendezvous with the gunboat SMS Eber , which transferred naval officers , ammunition and armaments to the liner , whose job now was to sink British merchant shipping rounding Cape Horn . She was armed with two 4 . 1 " guns and six pom - poms , all manned by experienced naval personnel , and she was supplied by some of the multitude of German colliers which found themselves trapped on the South American coast by the outbreak of war . She was given the codename " Hilfskreuzer B " ( Auxiliary Cruiser B ) and was commanded by Korvettenkapitän ( Lieutenant Commander ) Wirth , who took her to the Brazilian islands of Trindade , 500 miles east of the Brazilian mainland , where the German Navy had established a small , secret supply base . It was at this base on 14 September 1914 that the " Cap Trafalgar " was discovered by the British armed merchant cruiser HMS Carmania , a liner belonging to the Cunard Line which had been converted to a convoy escort and raider designed to flush out German colliers and small warships that might be using the inhospitable island as a base against British merchant shipping . " Carmania " spotted " Cap Trafalgar ' s " smoke early in the morning and some hours later was able to surprise the German ship with two colliers in the island ' s only harbour . By ironic coincidence the " Cap Trafalgar " was disguised as the " Carmania " ; while the " Carmania " was not disguised as the " Cap Trafalgar " , some accounts were confused . Both captains realised that to fight a successful action they required plenty of room , and so separately steamed several miles from the outcrop in order to gain the space required . The " Cap Trafalgar " also sent out encoded German messages , announcing the engagement with the " Carmania " , and the position as 35 degrees west , 26 degrees south , with a NNW heading . Then the two ships turned towards each other and began to fight , the " Carmania " firing too early and thus allowing the " Cap Trafalgar " the first blow . " Carmania " suffered much the worse of the engagement in the ensuing two hours , being hit 79 times , was holed below the waterline , and had her bridge totally destroyed by shellfire . However , as the range closed her own guns began to tell , and fires broke out on both ships , sailors lining the rails and firing machine guns at their opposite numbers as the ships came within a few hundred yards of each other , in a style of fighting more akin with the Napoleonic Wars than the First World War . Just as it seemed that the fires on " Carmania " would burn out of control , " Cap Trafalgar " veered away , lowering lifeboats as she heeled over to port . A shell below the waterline had ruptured several compartments , and the ship was rapidly sinking , although the colliers were able to pull 279 sailors from the wreck before she sank . 51 were killed in the fighting or the sinking ( other reports say 16 or 17 lives were lost ) , including Captain Wirth . " Carmania " was equally shattered , listing severely , heavily flooded and burning , with nine men dead and many more wounded . It was at this point that " Cap Trafalgar ' s " contemporary , the armed merchant cruiser SMS " Kronprinz Wilhelm " arrived , seemingly to provide the " coup de grace " for the shattered ship . However , the " Kronprinz Wilhelm ' s " captain feared a trap , since many ships both German and Allied in the area had doubtless been listening to the SOS calls of the " Cap Trafalgar " , which , though in German code , had been supplemented by messages from the " Carmania " with the British code . Since multiple warships were on their way to the location , and the " Cap Trafalgar " had presumably already sunk , the captain of the " Kronprinz Wilhelm " turned his ship about and sailed away without firing a shot . ( Von Niezychowski , 1928 ) The following day the " Carmania " was rescued and brought into Pernambuco by other units of the Royal Navy , whilst the survivors of the " Cap Trafalgar " were deposited at Montevideo by the colliers , from where they would attempt to make their way home .