When World War I began, Titanic's sister ship RMS Olympic initially remained in commercial service, but in May 1915 she was requisitioned as a troop transport. Her many trips carrying Canadian troops made her a favorite symbol in the City of Halifax.

After the United States declared war on Germany in 1917, Olympic also transported thousands of U.S. troops to Britain. In the early hours of 12 May, 1918, Olympic sighted a surfaced U-boat 1,600 ft ahead. Her gunners opened fire and she turned to ram the submarine, which crash-dived. Olympic struck the U-boat just aft of the conning tower and her port propeller sliced through the pressure hull, critically disabling it.

American soldiers on board paid for a plaque to be placed in one of Olympic's lounges to commemorate the event, it read: "This tablet presented by the 59th Regiment United States Infantry commemorates the sinking of the German submarine U103 by the Olympic on May 12th, 1918 in latitude 49 degrees 16 minutes north longitude 4 degrees 51 minutes west on the voyage from New York to Southampton with American troops"

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