On 24 August 1939, she was taken into naval service and converted into an Armed Merchant Cruiser. Armed with 8 x 6-inch (152mm) and 2 x 3-inch (76mm) naval guns, she became HMS "Ascania" with the pennant number F68. She sailed with the Halifax Escort Force and later with the North Atlantic Escort Force on convoy protection duty. From November 1941 to September 1942 she deployed to the New Zealand station. In October 1942, she was returned to the UK and was employed as a Troopship by the Ministry of War Transport. The following year, "Ascania" was modified into a Landing Ship Infantry and took part in the Invasion of Sicily in 1943, and the Anzio Landings and landings in the south of France in 1944.