Carmania, 19,650 tons, was built in 1905 for Cunard's Liverpool to New York supplementary service and during the winter months either relieved the regular mail steamers or sailed from Fiume on the American tourist route to and from the Mediterranean. Cap Trafalgar, 18,700 tons, was built in 1913 for the Hamburg-South American Line's Buenos Aires service and both vessels were converted to armed Merchant Cruisers on the outbreak of the Great War.
On the morning of the 14th September, off the western end of the island of Trinidad, Cap Trafalgar was surprised in the act of coaling by the Carmania, under the command of Captain Grant, R.N. At first she made off at high speed, but later turned about and prepared to engage. Both ships began firing at 7,500 yards, the 4.7-in. guns of the Carmania doing great damage to the hull of the enemy. The fire from the Cap Trafalgar was initially too high, but as the ships closed she began to score, setting the Carmania on fire under the forebridge and cutting her main water pipe so that the fire could not be brought under control. After an engagement lasting one hour and forty minutes, the Cap Trafalgar was ablaze and sinking. Towards the end of the action, she attempted to escape but her engines were not equal to the strain and she finally capsized to port and sank by the head. Five boats crowded with survivors were picked up by the German colliers, the Carmania being still on fire and too badly mauled to render assistance.
Carmania herself survived and was, in fact, the only Armed Merchant Cruiser ever to have sunk a similar antagonist in a straight gun duel; when, after extensive repairs, she returned to sea, she found herself with an unrivalled reputation which outlived her long after she was broken up in 1932.