Auxiliary cruiser

An auxiliary cruiser is a merchant ship, usually a fast passenger liner, that a navy has taken over, armed and manned with its own crew. Unlike a merchant ship armed only for self-defence, it was a warship. In the First World War the British used such ships mainly for blockade patrols and escort duty, the Germans as raiders on the trade routes.

Liners in naval service

As early as the late 19th century Britain and Germany asked shipowners to design fast steamers on which guns could be mounted in wartime. On 3 August 1914 a royal proclamation allowed the government to requisition British merchant ships, and the largest and fastest liners were converted into auxiliary cruisers. They had a long range, carried plenty of coal and could overtake most merchant ships, but their familiar silhouettes were easy to recognise.

German raiders

On 4 August 1914 Kaiser Wilhelm der Grosse, until recently a luxury liner, sailed from Bremerhaven. On 26 August the cruiser Highflyer caught her off the coast of Río de Oro, and after an exchange of fire her crew scuttled the damaged ship. On 14 September two armed liners met off the island of Trindade: the British Carmania sank the German Cap Trafalgar, though she herself was badly damaged.

Other German auxiliary cruisers ended their cruises in neutral ports, often out of coal. In December 1914 Cormoran was interned at Guam, an American island. Prinz Eitel Friedrich, which had sunk the American barque William P. Frye, agreed to internment at Newport News in April 1915, and less than three weeks later so did Kronprinz Wilhelm, the last raider then at large on the oceans.

Germany then turned to ordinary freighters with hidden guns, which approached their victims under a false flag. Möwe, disguised as a freighter, put to sea on 29 December 1915. On her first cruise she sank or captured 15 ships, and her mines sank a British battleship. Wolf returned to Kiel after 451 days at sea, and even a sailing ship, Seeadler, served as a raider.

British patrols and escorts

In the north auxiliary cruisers replaced the obsolete cruisers of the 10th Cruiser Squadron, which from 1914 watched the waters between Scotland and Norway. By the time it was disbanded on 29 November 1917 it had inspected almost 13,000 merchant ships. It lost the cruiser Hawke and ten auxiliary cruisers.

Their work consisted mainly of stopping ships, which could be dangerous. On 29 February 1916, near Shetland, Alcantara stopped a freighter flying the Norwegian flag. She was the raider Greif, and both ships sank in the fight. The French auxiliary cruiser Europe stopped in February 1915 the American steamer Dacia, carrying cotton which her papers showed was bound for Bremen.

Auxiliary cruisers also accompanied squadrons and escorted convoys. Otranto sailed with Cradock’s squadron and survived the Battle of Coronel, and in 1918, fitted out as a troopship, she sank after a collision off the island of Islay. About 470 people died. In the summer of 1917 four auxiliary cruisers of the 10th Squadron were sent to escort the regular convoys across the Atlantic.

The dispute over armed ships

The line between an auxiliary cruiser and a ship armed for defence was disputed. London insisted that its merchant ships carried guns only for defence. In February 1916, however, Germany announced that it would treat armed Entente ships as warships. It cited secret Admiralty instructions which told masters to open fire on submarines pursuing them.