Empire Shelter was a ship originally laid down as the Castle-class corvette HMS Barnard Castle of the Royal Navy (pennant number K594), but converted to a convoy rescue ship before completion. Convoy rescue ships accompanied some Atlantic convoys to rescue survivors from ships which had been attacked. Conversion to rescue service involved enlarging galley and food storage areas and providing berthing and sanitary facilities for approximately 150 men. Scrambling nets were rigged along the sides, and boats suitable for open sea work were substituted for normal lifeboats. Rescue ships normally included a small operating room for an embarked naval doctor and sick bay staff.