and later Royal Air Force fighters to intercept German airships operating over the North Sea. Interwar years Caroline remained in the 4th Light Cruiser Squadron after World War I and in June 1919 went with the rest of the squadron to serve on the East Indies Station. In February 1922 she paid off into dockyard control and was placed in reserve. She came out of reserve in February 1924 to become a headquarters and training ship for the Royal Naval Volunteer Reserve's Ulster Division at Belfast, Northern Ireland, officially beginning those duties on 1 April 1924. Harland and Wolff of Belfast removed her weaponry and some of her boilers around 1924, after her arrival in Belfast. Her guns were pooled with those of other decommissioned cruisers and used to reinforce the coastal defences of the Treaty Ports. Second World War From 1939 until 1945, during the Second World War, Caroline served as the Royal Navy's headquarters in Belfast Harbour, which was used as a home base by many of the warships escorting Atlantic and Arctic convoys, including s of the 3rd Escort Group. As Belfast developed into a major naval base during the Second World War, its headquarters outgrew the confines of HMS Caroline herself and occupied different establishments in various parts of the city. Eventually several thousand ratings were wearing Caroline cap tallies. The first such establishment was set up in the Belfast Custom House. Later, Belfast Castle was taken over and included a radio station. There were depth charge pistol and Hedgehog repair workshops associated with HMS Caroline, some of which would have been on the quays beside her berth in Milewater Basin. During the early part of the Second World War when RAF Belfast occupied Sydenham (Belfast harbour) airfield, Fleet Air Arm personnel based there were lodged under HMS Caroline. In 1943, the airfield was transferred to the Admiralty and commissioned as . Postwar After the Second World War, the Royal Navy returned Caroline to the Royal Naval Volunteer Reserve, and she served as its last afloat training establishment. She underwent a refit at Harland and Wolff in Belfast in 1951. The Royal Naval Reserve Unit decommissioned from the ship in December 2009, moved ashore, and recommissioned as the "stone frigate" (i.e., shore establishment) . Caroline herself was decommissioned on 31 March 2011 in a traditional ceremony. Her ensign was laid up in St Anne's Cathedral in