RMS Olympic was converted into the troopship HMT Olympic during World War I.
After the First World War began, Olympic was requisitioned for military service and adapted to carry troops. She transported thousands of personnel between Britain and the battlefront, operating under the designation HMT Olympic. Her size made her valuable for moving large numbers of soldiers.
In 1918, Olympic rammed and sank the German submarine U-103 in the western approaches to the English Channel. She was the only merchant ship known to have sunk an enemy warship during the First World War. The incident added to her reputation for robust construction and successful wartime service.
Olympic returned to civilian service after the war and was refitted to burn oil rather than coal. That conversion improved operating efficiency. Her wartime role is sometimes confused with Britannic’s hospital-ship service, but Britannic served as HMHS Britannic and never returned to commercial operation.