His Majesty's Naval Base, Clyde (HMNB Clyde; also HMS Neptune), primarily sited at Faslane on the Gare Loch, is one of three operating bases in the United Kingdom for the Royal Navy (the others being HMNB Devonport and HMNB Portsmouth). It is the navy's headquarters in Scotland and is best known as the home of Britain's nuclear weapons, in the form of nuclear submarines armed with Trident missiles.
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👉 HMNB Clyde in the context of Nuclear weapons of the United Kingdom
In 1952, the United Kingdom became the third country (after the United States and the Soviet Union) to develop and test nuclear weapons, and is one of the five nuclear-weapon states under the Treaty on the Non-Proliferation of Nuclear Weapons. As of 2025, the UK possesses a stockpile of approximately 225 warheads, with 120 deployed on its only delivery system, the Trident programme's submarine-launched ballistic missiles. Additionally, United States B61 nuclear bombs have been stored at RAF Lakenheath since 2025. In 2025, the UK announced plans to procure 12 F-35A aircraft capable of delivering B61s.
Since 1969, the Royal Navy has operated the continuous at-sea deterrent, with at least one ballistic missile submarine always on patrol. Under the Polaris Sales Agreement, the US supplied the UK with Polaris missiles and nuclear submarine technology, in exchange for the general commitment of these forces to NATO. In 1982, an amendment allowed the purchase of Trident II missiles, and since 1998, Trident has been the only nuclear weapons system in British service. Four Vanguard-class submarines are based at HMNB Clyde in Scotland. Each is armed with up to sixteen Trident II missiles, each carrying warheads in up to eight multiple independently targetable re-entry vehicles (MIRVs).
In this Dossier
- ⭐ Core Definition: HMNB Clyde
- 👉 HMNB Clyde in the context of Nuclear weapons of the United Kingdom
- HMNB Clyde in the context of HMNB Portsmouth
- HMNB Clyde in the context of His Majesty's Naval Service
- HMNB Clyde in the context of Captain (naval)
- HMNB Clyde in the context of Plymouth Dockyard
- HMNB Clyde in the context of Serco Marine Services
- HMNB Clyde in the context of Vanguard-class submarine
HMNB Clyde in the context of HMNB Portsmouth
His Majesty's Naval Base, Portsmouth (HMNB Portsmouth) is one of three operating bases in the United Kingdom for the Royal Navy (the others being HMNB Clyde and HMNB Devonport). Portsmouth Naval Base is part of the city of Portsmouth; it is located on the eastern shore of Portsmouth Harbour, north of the Solent and the Isle of Wight. For centuries it was officially known as HM Dockyard, Portsmouth: as a Royal Navy Dockyard, Portsmouth functioned primarily as a state-owned facility for building, repairing and maintaining warships; for a time it was the largest industrial site in the world.
From the 1970s, the term 'Naval Base' began to be used for Portsmouth (and other Royal Dockyards), acknowledging a greater focus on personnel and support elements alongside the traditional industrial emphases. In 1984 Portsmouth's Royal Dockyard function was significantly downsized and downgraded, and was formally renamed the 'Fleet Maintenance and Repair Organisation' (FMRO). The FMRO was privatised in 1998; in 2002, shipbuilding (which had not taken place on site since the late 1960s) resumed in the form of block construction, but this again ceased in 2014.
HMNB Clyde in the context of His Majesty's Naval Service
His Majesty's Naval Service, referred to colloquially as the Royal Navy, after the primary fighting arm of the service, is the United Kingdom's naval warfare and maritime service. It consists of the Royal Navy, Royal Marines, Royal Fleet Auxiliary, Royal Naval Reserve, Royal Marines Reserve and Naval Careers Service. The Naval Service as a whole falls under the command of the Navy Board, which is headed by the First Sea Lord. This position is currently held by General Sir Gwyn Jenkins (appointed May 2025). The Defence Council delegates administration of the Naval Service to the Admiralty Board, chaired by the Secretary of State for Defence.
The Naval Service is dominated by the Royal Navy, and operates primarily from three bases in the United Kingdom where commissioned ships are based; Portsmouth, Clyde and Devonport, the last being the largest operational naval base in Western Europe. As of December 2025, there were about 90 vessels in service with the various branches of the Naval Service, plus more than 90 additional vessels operated by the supporting Serco Marine Services. These vessels included: 63 commissioned ships of the Royal Navy, 17 principal landing craft of the Royal Marines, 10 auxiliary ships of the Royal Fleet Auxiliary and 90+ supporting Marine Services vessels. Additional vessels are under charter to the Ministry of Defence. As of 2022, HM Naval Service (Royal Navy, Royal Marines, Royal Fleet Auxiliary and Naval Careers Service) employed about 39,500 regular and reserve personnel.
HMNB Clyde in the context of Captain (naval)
Captain is the name most often given in English-speaking navies to the rank corresponding to command of the largest ships. The rank is equal to the army rank of colonel and air force rank of group captain.
Equivalent ranks worldwide include ship-of-the-line captain (e.g. France, Argentina, Spain), captain of sea and war (e.g. Brazil, Portugal), captain at sea (e.g. Germany, Netherlands) and "captain of the first rank" (Russia).
HMNB Clyde in the context of Plymouth Dockyard
His Majesty's Naval Base, Devonport (HMNB Devonport) is one of three operating bases in the United Kingdom for the Royal Navy (the others being HMNB Clyde and HMNB Portsmouth) and is the sole nuclear repair and refuelling facility for the Royal Navy. HMNB Devonport is located in Devonport, in the west of the city of Plymouth, England.
The base began as a Royal Navy Dockyard in the late 17th century, designed and built on open ground by Edmund Dummer as an integrated facility for the repair and maintenance of warships, centred on his pioneering stone dry dock (one of the earliest stepped docks in the world). Over the next two centuries it expanded, reaching its present extent in the 20th century. Historically, the yard was also used for shipbuilding: over 300 naval vessels were built there, the last being HMS Scylla (launched in 1968).
HMNB Clyde in the context of Serco Marine Services
Serco Marine Services is a Private Finance Initiative contract, with Serco Group, to deliver auxiliary services to His Majesty's Naval Service (incl. Royal Navy, Royal Marines and Royal Fleet Auxiliary).
Marine Services primarily operates from the nation's three main naval bases, HMNB Portsmouth, HMNB Devonport and HMNB Clyde, but also supports training and operations overseas, as well as at various British Overseas Territories.
HMNB Clyde in the context of Vanguard-class submarine
The Vanguard class is a class of nuclear-powered ballistic missile submarines (SSBNs) in service with the Royal Navy. The class was introduced in 1994 as part of the Trident nuclear programme, and comprises four vessels: Vanguard, Victorious, Vigilant and Vengeance, built between 1986 and 1999 at Barrow-in-Furness by Vickers Shipbuilding and Engineering, now owned by BAE Systems. All four boats are based at HM Naval Base Clyde (HMS Neptune), 40 km (25 mi) west of Glasgow, Scotland.
Since the decommissioning of the Royal Air Force WE.177 free-fall thermonuclear weapons during March 1998, the four Vanguard submarines are the sole platforms for the United Kingdom's nuclear weapons. Each submarine is armed with up to 16 UGM-133 Trident II missiles. The class is scheduled to be replaced starting in the early 2030s with the Dreadnought-class submarine.