Invergordon became a full-scale Royal Navy base during the First World War, providing fuel oil, water, and dockyard repair facilities. At its peak, approximately 20,000 people lived in and around Invergordon, with military camps ringing the Firth. On 30 December 1915, the cruiser HMS Natal blew up and capsized off Invergordon during a Christmas film party hosted by the captain for officers' wives, children, and nurses from a nearby hospital ship, with the loss of at least 390 lives.