An armed merchantman is a merchant ship equipped with guns, usually for defensive purposes, either by design or after the fact. In the days of sail, piracy and privateers, many merchantmen would be routinely armed, especially those engaging in long distance and high value trade. In more modern times, auxiliary cruisers were used offensively as merchant raiders to disrupt trade chiefly during both World War I and World War II, particularly by Germany.
RMS Transylvania was a British ocean liner. She was launched on 11 March 1925 for the Anchor Line and was the sister ship to the SS California and RMS Caledonia. She was converted into an armed merchant cruiser, pennant F56 during World War II. On 10 August 1940, HMS Transylvania was torpedoed and sunk by the German U-boat U-56.
HMS Rawalpindi was a British armed merchant cruiser that was sunk in a surface action against the German battleships Scharnhorst and Gneisenau during the first months of the Second World War. Her captain was Edward Kennedy.
RMS Majestic was a British ocean liner working on the White Star Line’s North Atlantic run, originally launched in 1914 as the Hamburg America Liner SS Bismarck. At 56,551 gross register tons, she was the largest ship ever operated by the White Star Line under its own flag and the largest ship in the world until completion of SS Normandie in 1935.
RMS Carmania was a Cunard Line transatlantic steam turbine ocean liner. She was launched in 1905 and scrapped in 1932. In World War I she was first an armed merchant cruiser (AMC) and then a troop ship.
RMS Maloja was a British ocean liner that saw service from 1923 to 1954.
RMS Campania was a British ocean liner owned by the Cunard Line, built by Fairfield Shipbuilding and Engineering Company of Govan, Scotland, and launched on Thursday, 8 September 1892.
RMS Antonia and her sister ship Andania were the first two of the six 14,000 ton "A" ocean liners built for Cunard in the early 1920s.
RMS Andania was a British ocean liner launched in 1921. She was the first of six 14,000-ton A-class liners built for the Cunard Line in the early 1920s. The other ships were Antonia, Ausonia, Aurania, Ascania, and Alaunia.
RMS Carinthia was first laid down in Barrow-in-Furness in 1924 with the yard number Hull 586. Originally she had the name Servia but was renamed at the time of her launching on 24 February 1925. She made her maiden voyage on 22 August 1925 from Liverpool to New York City. At her launch she was the largest of the five post First World War intermediate size liners.
RMS Ausonia, launched in 1921, was one of Cunard's six post-World War I "A-class" ocean liners for the Canadian service.
SS California was a British 16,792 GRT steam turbine ocean liner built in Glasgow in 1923 for the Anchor Line. She was a sister ship of Cameronia, Tyrrhenia, Tuscania, Transylvania and Caledonia. In 1939 the Royal Navy requisitioned her. She was bombed and abandoned along with the Duchess of York west of Spain by a Luftwaffe attack in July 1943.
HMS Artifex was a repair ship of the Royal Navy from late in the Second World War and into the Cold War. Launched as the Cunard liner RMS Aurania she was requisitioned on the outbreak of war to serve as an armed merchant cruiser. Damaged by a U-boat while sailing with an Atlantic convoy, she was purchased outright and converted to a floating workshop, spending the rest of her life as a support ship for the navy.
RMS Corfu was a Royal Mail Ship and ocean liner operated by the Peninsular and Oriental Steam Navigation Company. Known as one of the 'Far East Sisters', she was launched in 1931 to serve the company's India and Far East Mail Service, along with her sister ship, the RMS Carthage. Both ships were built by Alexander Stephen & Sons Ltd in Glasgow, Scotland and served from 1931 until 1961 when they were scrapped in Japan.
The RMS Ascania was an ocean liner operated by the Cunard Line. She was launched on 20 December 1923 at the Armstrong Whitworth Shipbuilders Ltd yard in Newcastle-upon-Tyne; the fifth of Cunard's six "A" class liners. Due to unforeseen cost overruns, the vessel was not completed until May 1925. Following service in a number of military roles during the Second World War, she was refitted and returned to civilian use in 1950, finally retiring in 1956.
The SS Ranpura was a British passenger and cargo carrying ocean liner built by R. & W. Hawthorn Leslie and Company at Newcastle upon Tyne for the Peninsular & Oriental Steam Navigation Company in 1924. She was the first of the P&O 'R' class liners that had much of their interiors designed by Lord Inchcape's daughter Elsie Mackay. She was launched 13 September 1924 and sponsored by C.C. Straker, wife of the chairman of Hawthorn Leslie and Company.
RMS Otranto was an ocean liner that was built for the Orient Steam Navigation Company in 1925. The "RMS" prefix stands for Royal Mail Ship, as she carried overseas mail under a contract between Orient Line and Royal Mail. Otranto was in service until 1957, when she was sold for scrap.
SS Cathay was a P&O passenger steamship that was built in Scotland in 1925 and sunk in the Mediterranean Sea in 1942. In the Second World War she was first an armed merchant cruiser and then a troop ship. In 1942 she took part in Operation Torch, and was sunk in a German air raid off Bougie, Algeria.
RMS Asturias was a Royal Mail Lines ocean liner that was built in Belfast in 1925. She served in the Second World War as an armed merchant cruiser until she was crippled by a torpedo in 1943. She was out of action until 1948 when she returned to civilian service as an emigrant ship. She became a troop ship in 1954 and was scrapped in 1957.
Several ships have borne the name Caledonia for Caledonia:
United Kingdom 
