Gibraltar's defence is the responsibility of the tri-service British Forces Gibraltar. The army garrison is provided by the Royal Gibraltar Regiment, originally a part-time reserve force which was placed on the permanent establishment of the British Army in 1990. The regiment includes full-time and part-time soldiers recruited from Gibraltar, as well as British Army regulars posted from other regiments. The Royal Navy maintains a squadron at the Rock. The squadron is responsible for the security and integrity of British Gibraltar Territorial Waters (BGTW). The shore establishment at Gibraltar is called Rooke after Sir George Rooke who captured the Rock for Archduke Charles (pretender to the Spanish throne) in 1704. Gibraltar's strategic position provides an important facility for the Royal Navy and Britain's allies. Ships from the Spanish Navy do not call at Gibraltar. British and U.S. nuclear submarines frequently visit the Z berths at Gibraltar. A Z berth provides the facility for nuclear submarines to visit for operational or recreational purposes, and for non-nuclear repairs. The Royal Air Force station at Gibraltar forms part of Headquarters British Forces Gibraltar. Although aircraft are no longer permanently stationed at RAF Gibraltar, a variety of RAF aircraft make regular visits to the Rock and the airfield also houses a section from the Met Office. The Rock is believed to be a SIGINT listening post. Its strategic position provides a key GCHQ and National Security Agency location for Mediterranean and North African coverage. During the Falklands War, an Argentine plan to attack British shipping in the harbour using frogmen (Operation Algeciras) was foiled. The naval base also played a part in supporting the task force sent by Britain to recover the Falklands. In January 2007, the Ministry of Defence announced that services to the base would be provided by the private company SERCO, resulting in industrial action from the trade unions involved.