The Cap Trafalgar was a new, large and luxurious liner that in April 1914 was brought into service by the Hamburg-Sud Amerika Line for service between Germany and the River Plate.
At the outbreak of war she was at Buenos Aires, where the German navy requisitioned her as an auxiliary cruiser. After coaling at Montevideo she sailed for the remote Brazilian island of Trinidade, 500 miles off the mainland. There, she met the old gunboat SMS Eber, which transferred her armament of two 105mm (4.1 inch) guns and six one pounders, their ammunition and some of her crew to Cap Trafalgar, which was to raid merchant shipping under the command of Korvettenkapitän Wirth.
Cap Trafalgar’s first commerce raiding cruise was a failure. According the British Official Histories, the quantity of wireless signals from British cruisers had discouraged her from approaching the main trade routes. On 13 September she returned to Trinidade in order to coal from two colliers.
The next day, HMS Carmania, a Cunard liner that had been armed for trade protection duties, visited Trinidade, which the British suspected might be used by German commerce raiders to coal. Carmania and Cap Trafalgar were of similar size, about 19,000 tons, but the British ship had a much bigger armament: eight 4.7 inch guns. Both were designed for 18 knots, but Robert Massie says that the British ship could make only 16 knots.
The National Maritime Museum at Greenwich in London owns a painting of the action, which is reproduced on its website. The caption says that Cap Trafalgar had been modified and painted to resemble Carmania.
The German ships set sail once they saw Carmania approaching. They seemed initially to be fleeing, but Cap Trafalgar then turned towards the enemy. Julian Corbett speculates in the Royal Navy’s Official History that Wirth may have realised that his opponent was another armed liner rather than a warship.
Neither ship had the fire control systems or ammunition hoists of a modern warship, so the action was fought in the style of Nelson’s day, with ammunition being brought to the guns by hand and the guns firing as the target bore.
Carmania’s captain, Noel Grant, ordered a warning shot to be fired at 12:10 pm at 8,500 yards range. Carmania began to fire her port guns at 7,500 yards, with Cap Trafalgar replying. At 4,500 yards the British switched to firing salvoes, the second and third of which hit the German ship on her waterline. The Germans scored a significant number of hits, but most of them were high, hitting Carmania’s masts, funnels, ventilators and bridge.
At 3,500 yards the German one pounders were in range and the barrels of the elderly British guns were red hot. Grant turned his ship in order the fire with the starboard guns.
Both ships were now on fire and Cap Trafalgar was listing. Wirth tried to use his ship’s superior speed to escape and succeeded in getting outside Carmania’s 9,000 yard gun range by 1:30. However, Cap Trafalgar was too badly damaged to escape, and she sank with colours flying at 1:45. Wirth went down with her.
Carmania had been hit 79 times. Many were high but five holes were on the waterline, and she was one fire, leaving her in no position to rescue Cap Trafalgar’s survivors. Nine of her crew had been killed and 26 wounded. Grant also feared that smoke that could be seen to the north might come from a German cruiser that Cap Trafalgar had been radioing. In fact it was from one of her colliers, the Eleonore Woermann, which picked up the German survivors.
The only source consulted to give German casualties is Wikipedia, which says that 279 Germans were rescued and between 16 and 51 were killed. Conway’s says that Cap Trafalgar’s crew was 319, implying a number at the top of that range.
 J. S. Corbett, H. Newbolt, Naval Operations, 5 vols. (London: HMSO, 1938). vol. i, p. 307; C. E. Fayle, Seaborne Trade., 3 vols. (London: HMSO, 1920). vol. i, p. 223.
 R. K. Massie, Castles of Steel: Britain, Germany, and the Winning of the Great War at Sea (London: Jonathan Cape, 2004), p. 206.
 Corbett, Newbolt, Naval. vol. i, p. 307.
 R. Gray, Conway’s All the World’s Fighting Ships, 1906-1921 (London: Conway Maritime Press, 1985), p. 184.