US nuclear weapons in British service

Production of British nuclear weapons was slow and Britain had only ten atomic bombs on hand in 1955 and just fourteen in 1956.^[173] At the three-power Bermuda Conference with Eisenhower in December 1953, Churchill suggested that the United States allow Britain to have access to American nuclear weapons to make up the shortfall.^[174] The provision on American weapons was called Project E.^[175] The agreement was confirmed by Eisenhower and Macmillan, who was now the Prime Minister, during their March 1957 meeting in Bermuda,^[176]^[177] and a formal Memorandum of Understanding (MOU) was signed on 21 May 1957.^[178]^[179]

Four squadrons of English Electric Canberra bombers based in Germany were equipped with US Mark 7 nuclear bombs stored at RAF Germany bases. There were also four squadrons of nuclear-armed Canberras based in the UK, which were capable of carrying either the Mark 7 or Red Beard. They too were assigned to the SACEUR in October 1960.^[180] The planned V-bomber force was reduced to 144 aircraft, and it was intended to equip half of them with Project E weapons,^[181] so 72 Mark 5 nuclear bombs were supplied for the V-bombers.^[182]^[183] When the MDA came into force, the US agreed to supply the V-bombers with megaton weapons in place of the Mark 5,^[184] in the form of Mark 15 and Mark 39 nuclear bombs.^[182]

Under the Project E MOU, US personnel had custody of the weapons. This meant they performed all the tasks related to their storage, maintenance and readiness. The bombs were stored in Secure Storage Areas (SSAs) on the same bases as the bombers which British staff were not permitted to enter. It was therefore impossible to store British and American bombs together in the same SSA.^[185] US custody also created operational problems. The procedure for handing over the bombs added an extra ten minutes to the bombers' reaction time,^[186] and the requirement that US personnel had guardianship of the weapons at all times meant that neither they nor the bombers could be relocated to dispersal airfields as the RAF desired.^[187] The operational restrictions imposed by Project E "effectively handed the US government a veto over the use of half of Britain's nuclear deterrent".^[188]

The Air Council decided on 7 July 1960 that Project E weapons would be phased out by December 1962, by which time it was anticipated that there would be sufficient British megaton weapons to equip the entire strategic bomber force.^[189] Project E weapons were replaced by British Yellow Sun bombs.^[190] Problems encountered in the development of Red Beard meant that the replacement of kiloton weapons took longer than anticipated.^[191] The Air Ministry decided to replace the Canberras with Valiants as the long-range Vulcan and Victor V bombers became available. A Valiant squadron at RAF Marham was assigned to SACEUR on 1 January 1961, followed by two more in July. The UK-based Canberra squadrons were then disbanded. Each of the 24 Valiants was equipped with two Project E Mark 28 nuclear bombs.^[180] These were replaced by the newer Mark 43 nuclear bombs in early 1963.^[180] The Valiants were withdrawn from service in 1965.^[192]

Project E nuclear warheads were also used on the sixty Thor Intermediate Range Ballistic Missiles (IRBMs) that were operated by the RAF from 1959 to 1963 under Project Emily.^[193] During the Cuban Missile Crisis, the RAF's bombers and Thor missiles targeted 16 cities, 44 airfields, 10 air defence control centres and 20 IRBM sites.^[194] The RAF high command never warmed to missiles, and always ranked them secondary to the V bomber force. The missile bases were separate from the rest of the RAF and its personnel considered outside the mainstream. Project Emily gave the RAF considerable experience in missile operations, but the 1960 cancellation of Blue Streak in favour of the American Skybolt, an air-launched ballistic missile, rendered this expertise of dubious value.^[195] An Air Council meeting on 31 May 1962 decided that Project Emily should be terminated by the end of 1963,^[196] and the last Thor squadrons were inactivated on 23 August 1963.^[197]

The British Army purchased 113 Corporal missiles from the United States in 1954. It was intended that they would be equipped with British warheads under a project codenamed Violet Vision, but Project E offered a quicker, simpler and cheaper alternative.^[198] The US supplied 100 W7 warheads, which had to be drawn from US Army storage sites in southern Germany until arrangements were made for local storage in August 1959.^[199]^[200] A British missile, Blue Water, with an Indigo Hammer warhead, was developed to replace Corporal. The US offered the Honest John missile as an interim replacement. The offer was accepted, and 120 Honest John missiles with W31 warheads were supplied in 1960, enough to equip three artillery regiments.^[200]^[201] Blue Water was cancelled in July 1962,^[202] and Honest John remained in service until 1977, when it was replaced by the Lance missile.^[200] The US also supplied the British Army of the Rhine (BAOR) with 36 W33 nuclear warheads that equipped four batteries of eight-inch M115 howitzers. These were later replaced by M110 howitzers.^[200]^[201] The British Army deployed more US nuclear weapons than the RAF and Royal Navy combined, peaking at 327 out of 392 in 1976–1978.^[203]

A maritime version of Project E, known as Project N supplied US Navy weapons. Providing American atomic bombs for Royal Navy ships would have involved similar dual key arrangements and detachments of US Marines on board Royal Navy ships, which was deemed impractical even for ships and weapons dedicated to use in European waters. However, RAF Coastal Command acquired Mk 101 Lulu nuclear depth bombs (with the W34 nuclear warhead) for its Avro Shackleton and Hawker Siddeley Nimrod maritime patrol aircraft from 1965 to 1971 under Project N.^[204]^[205] These were later replaced by the more capable Mark 57, which was stockpiled at RAF St Mawgan and RAF Machrihanish.^[206]

When the Cold War ended in 1991, the BAOR still had about 85 Lance missiles, and more than 70 W33 eight-inch and W48 155 mm nuclear artillery shells. The last Project E warheads, including the Mark 57 nuclear depth bombs and those used by the BAOR, were withdrawn in July 1992.^[207]

US nuclear weapons in US service in the UK

In the early years of the Cold War, the majority of the bomber force of the US Strategic Air Command (SAC) was made up of World War II vintage Boeing B-29 Superfortress bombers, and their successors, the Boeing B-50 Superfortress and the Boeing B-47 Stratojet, all of which lacked the range to reach targets in the Soviet Union from bases in the continental United States. Only the small number of Convair B-36 Peacemaker bombers could do this. Overseas bases were therefore required, and the need for bases in the UK was a feature of American war planning for over a decade.^[208]

Obtaining British permission was easy thanks to the wartime comradeship between the RAF and the United States Army Air Forces (USAAF). Bypassing the politicians, General Carl Spaatz, the commander of the USAAF, came to an agreement with the Chief of the Air Staff, Marshal of the Royal Air Force Lord Tedder, in June and July 1946. Work began on extended and strengthened runways at RAF airbases in East Anglia to receive the B-29s. In June 1947, nine B-29s of the 97th Bombardment Group deployed to RAF Marham, where they were greeted by Tedder.^[209] This was merely a test; the bombers were not nuclear-capable. Only the Silverplate B-29s of the 509th Bombardment Group could do so.^[210] Their first deployment was in April 1949.^[211] Ninety sets of bomb assemblies—atomic bombs without the fissile cores—were stored in the UK by July 1950, and authority to deploy the cores as well was given in April 1954.^[212]

The 3rd Air Division was formed in 1949 to control the deployments of B-29s to the UK. It was soon upgraded to the status of a major command, and became the Third Air Force in May 1951 as part of the United States Air Forces in Europe. SAC then formed the 7th Air Division to control the nuclear bomber deployments.^[213] With the introduction to service of long-range bombers and intercontinental ballistic missiles, the need for a SAC presence in the UK diminished, On 3 April 1964, the last SAC aircraft, a B-47 from the 380th Bombardment Wing, left RAF Brize Norton, ending nearly 12 years' of continual B-47 deployments, and the 7th Air Division on 30 June 1964.^[214] During the later Cold War years, Boeing B-52 Stratofortress bombers became regular visitors to the United Kingdom, turning up at bases such as RAF Greenham Common and also taking part in RAF Bomber competitions, but were deployed to NATO on an individual basis, not as groups or wings. In 1962 there were one or two visits each month.^[215]

In fulfilment of NATO's plans to halt a Soviet invasion of Western Europe using tactical nuclear weapons, the 3rd Air Force received its own nuclear weapons when the 20th Fighter Wing deployed to RAF Wethersfield in Essex on 1 June 1952, with Republic F-84F Thunderstreak fighters and Mark 7 nuclear bombs. It reequipped with the North American F-100 Super Sabre in 1957, and the General Dynamics F-111 in 1970.^[216]^[217] In the 1970s, up to 60 F-111s based in the UK were on quick reaction alert, each carrying multiple B61 nuclear bombs.^[216]^[218] US Navy Polaris ballistic missile submarines were based at Holy Loch in Scotland from March 1961.^[219] During the 1980s nuclear armed USAF Ground Launched Cruise Missiles (GLCMs) were deployed at RAF Greenham Common and RAF Molesworth,^[220] as a consequence of the 1979 NATO Double-Track Decision, under which NATO countries agreed to modernise the alliance's nuclear weapons.^[221]

Under the terms of the 1987 Intermediate-Range Nuclear Forces Treaty with the Soviet Union, the United States withdrew its surface naval nuclear weapons and short-range nuclear forces. The GLCMs were withdrawn from the UK in 1991,^[207] and the Polaris submarine base at Holy Loch was closed in 1992.^[222]^[219] The US continued to store tactical nuclear weapons in the UK until 2008, when approximately 110 tactical B61s stored at RAF Lakenheath for deployment by USAF F-15E Strike Eagle aircraft were removed.^[223]^[207]^[224]^[225]

British nuclear weapons

Thumb — Yellow Sun, Britain's first production thermonuclear bomb

The MDA made fully developed and tested American designs available quickly and cheaply. The first of these was the Mark 28, which was "Anglicised" and manufactured in the UK as Red Snow. Exact copies of American designs were not pursued; the high explosive used in American warheads were more sensitive than British high explosive, and had caused fatal accidents in the US. Its use was not contemplated in the UK after an accident at Aldermaston on 28 February 1959 when two men were killed after a piece of British high explosive fell from a lorry. British high explosive was also bulkier, so a redesign was required.^[226]

Red Snow was far more economical in its use of fissile material than the Green Grass warhead in the Yellow Sun Mk.1 bomb, Britain's first production hydrogen bomb. A Yellow Sun Mk.2 with Red Snow, therefore, cost £500,000 compared to £1.2 million for the Mk.1. RAF Bomber Command wanted Violet Club replaced as soon as possible, so 37 Yellow Sun Mk.1s were delivered by the end of 1959. Deliveries of the Yellow Sun Mk.2 commenced in January 1961, and 43 were delivered by the end of the year. In November 1958. Red Snow also replaced Green Grass as the warhead in the Blue Steel stand-off missile.^[227]

The kiloton Red Beard was developed for use by the Canberras and the Royal Navy's Fleet Air Arm. Technical problems delayed its introduction into service,^[228] but over 100 were delivered by the end of 1961.^[229] Up to 48 Red Beards were secretly stowed in a highly secured weapons storage facility at RAF Tengah in Singapore between 1962 and 1971 for possible use by V bombers and for Britain's military commitment to SEATO.^[230]^[231]

The availability of US weapons and designs under the MDA led to the cancellation of several research projects. Indigo Hammer and the smaller Pixie were warheads intended for use with the Red Duster and Seaslug surface-to-air missiles; a British version of the US W44 was chosen instead.^[232] Blue Peacock, a 16,000-pound (7,300 kg) atomic demolition munition (ADMs) based on Blue Danube, was cancelled in 1958 in favour of the lighter Violet Mist, based on Red Beard. The development of the even smaller and lighter US ADMs led to its cancellation as well in 1961. ^[233]^[201] The US Medium Atomic Demolition Munition with the W45 was acquired instead.^[203] Yellow Anvil was a British artillery warhead that was cancelled in 1958.^[200]^[201]

In 1960, the government decided to cancel the Blue Streak missile based on the Chiefs of Staff's conclusion that it was too vulnerable to attack and thus was only useful for a first strike, and decided to purchase the American air-launched Skybolt missile instead.^[234] Macmillan met with Eisenhower in March 1960, and secured permission to buy Skybolt without strings attached. In return, the Americans were given permission to base the US Navy's Polaris-equipped ballistic missile submarines at Holy Loch in Scotland.^[235]

The Americans initially intended to pair Skybolt with the W47 warhead, an innovative light-weight design from the Lawrence Radiation Laboratory developed for Polaris. The British wanted to use Red Snow, partly for safety reasons and partly because it was not certain that the advanced M47 design would be made available without strings attached. The technical problem was that Red Snow was 1,000 pounds (450 kg) heavier, and therefore the range of the Skybolt would be reduced from 1,000 to 650 miles (1,610 to 1,050 km). A megaton design known as RE.179 based on the W49 warhead used in American ICBMs was developed for Skybolt.^[236]^[237]

At the same time, work was in progress on a Red Beard replacement for use with the RAF's BAC TSR-2 and the Royal Navy's Blackburn Buccaneer. Ultimately, a warhead was produced in two variants: the high-yield (300 to 450 kilotonnes of TNT (1,300 to 1,900 TJ)) WE.177B and the low-yield (0.5 or 10 kilotonnes of TNT (2.1 or 41.8 TJ)) WE.177A as a Red Beard replacement, and for use in depth charges and anti-submarine missiles. WE.177 was later adapted for use with Polaris, and would become the longest-serving British nuclear weapon.^[238]^[237]

The deployment of ships carrying nuclear depth bombs caused complications during the Falklands War, and in the aftermath of that war it was decided to stockpile them ashore in peacetime.^[239] When the US withdrew its theatre nuclear weapons from Europe, the British government followed suit. The nuclear depth bombs were withdrawn from service in 1992,^[237]^[240] followed by the WE.177 free-fall bombs on 31 March 1998, and all were dismantled by the end of August.^[241]

Research and production facilities

The Atomic Weapons Establishment (AWE), Aldermaston, formerly the Atomic Weapons Research Establishment (AWRE), is situated on a 750-acre (300 ha) site near Reading in Berkshire.^[242]^[243] It was built on the site of the former RAF Aldermaston, which was converted to nuclear weapons research, design and development establishment, and opened on 1 April 1950. In 1954, the AWRE took control of the nearby 225-acre (91 ha) ROF Burghfield, where warheads were assembled, and the test ranges at Foulness and Orford Ness. Components for nuclear weapons were also produced at the former ROF Cardiff site.^[243]^[244]

The Atomic Weapons Research Establishment became part of the United Kingdom Atomic Energy Authority on 1 January 1955.^[244] The last trials at Orford Ness were conducted on 9 June 1971, and the site was closed on 1 October 1971.^[245] Cardiff closed in 1997,^[243] and Foulness by the end of that year.^[246] In 1989, the government announced its intention to find a private company to run AWE, with the government retaining ownership of the site and control of AWE though a golden share arrangement. In 1993, the contract was awarded to a consortium of Hunting Engineering, Brown and Root and AEA Technology. In 1999, the contract was transferred to a consortium of BNFL, Lockheed Martin and Serco. In 2008, the British government sold the BNFL share to Jacobs Engineering Group.^[243]

Polaris

The Kennedy administration cancelled Skybolt in December 1962 because the United States Secretary of Defense, Robert McNamara, determined that other delivery systems were progressing better than expected, and a further expensive system was surplus to US requirements.^[247] In London, over one hundred Conservative members of Parliament, nearly one third of the parliamentary party, signed a motion urging Macmillan to ensure that Britain remained an independent nuclear power.^[248]

Macmillan met with President John F. Kennedy and brokered the Nassau Agreement. Macmillan rejected offers of other systems, and insisted that the UK needed to purchase Polaris submarine-launched ballistic missiles. These represented more advanced technology than Skybolt, and the US was not inclined to provide them except as part of a Multilateral Force within the North Atlantic Treaty Organization (NATO).^[249] In the end, Kennedy did not wish to see Macmillan's government collapse,^[250] which would imperil Britain's entry into the European Economic Community (EEC),^[251] so a face-saving compromise was reached: the US agreed to provide the UK with Polaris missiles, which would be assigned to NATO,^[252] and could be used independently only when "supreme national interests" intervened.^[253]

The Polaris Sales Agreement was signed on 6 April 1963.^[254] The UK retained its deterrent force, although its control passed from the RAF to the Royal Navy.^[255] The Polaris missiles were equipped with British warheads.^[256]^[257] A base was developed for the Polaris submarines at Faslane on the Firth of Clyde, not far from the US Navy's base at Holy Loch.^[258] It was served by a weapons store at nearby Coulport.^[259] The first of four Polaris submarines, HMS Resolution was launched in September 1966, and commenced its first deterrent patrol in June 1968.^[260] The annual running costs of the Polaris boats came to around two per cent of the defence budget, and they came to be seen as a credible deterrent that enhanced Britain's international status.^[261] British politicians did not like to talk about "dependence" on the United States, preferring to describe the Special Relationship as one of "interdependence".^[262]

Polaris had not been designed to penetrate anti-ballistic missile (ABM) defences, but the Royal Navy had to ensure that its small Polaris force operating alone, and often with only one submarine on patrol, could penetrate the ABM screen around Moscow.^[263] The Wilson government publicly ruled out the purchase of Poseidon missiles in June 1967, and without such a commitment, the Americans were unwilling to share information about warhead vulnerability.^[264] The result was Chevaline, an Improved Front End (IFE) that replaced one of the three warheads with multiple decoys and other defensive countermeasures, in what was known as a Penetration Aid Carrier (PAC).^[265] It was the most technically complex defence project ever undertaken in the United Kingdom.^[266] Chevaline's existence, along with its formerly secret codename, was revealed by the Secretary of State for Defence, Francis Pym, during a debate in the House of Commons on 24 January 1980.^[267] By this time the project had gone on for a decade.^[268] The final cost reached £1,025 million.^[269]

Trident

In 1982, the Thatcher government announced its decision to purchase 65 American Trident II D-5 missiles. These operated as part of a shared pool of weapons based at Naval Submarine Base Kings Bay in the United States. The US would maintain and support the missiles, while the UK would manufacture its own submarines and warheads. The warheads and missiles would be mated in the UK.^[270]^[271] Four Vanguard-class submarines were designed and built.^[272] Trident missiles had multiple independently targetable re-entry vehicle (MIRV) capability, which was needed to overcome the Soviet ABM defences.^[273]^[274]

Each submarine could carry up to 16 missiles, each of which can each carry up to 8 warheads. However, when the decision to purchase Trident II was announced, it was stressed that British Trident boats would carry no more than 128 warheads—the same number as Polaris. In November 1993, the Secretary of State for Defence, Malcolm Rifkind, announced that each boat would deploy no more than 96 warheads.^[222] In 2010, this was reduced to a maximum of 40 warheads, split between eight missiles.^[275]^[276] The missiles have a range of 12,000 kilometres (7,500 mi).^[277]

The first Trident boat, HMS Vanguard, collected a full load of 16 missiles in 1994, but the second, HMS Victorious drew only 12 in 1995, and the third, HMS Vigilant, 14 in 1997, leaving the remaining missile tubes empty.^[278] Although the UK designed, manufactured and owns the warheads, there is evidence that the warhead design is similar to, or even based on, the US W76 warhead fitted in some US Navy Trident missiles, with design data being supplied by the United States through the MDA.^[279]^[280]

Since 1969, the United Kingdom has always had at least one ballistic-missile submarine on patrol, giving it a nuclear deterrent that is, what the Defence Council described in 1980 as, "effectively invulnerable to pre-emptive attack".^[156] In the Strategic Defence Review published in July 1998, the government stated that once the Vanguard submarines became fully operational (the fourth and final one, HMS Vengeance, entered service on 27 November 1999), it would "maintain a stockpile of fewer than 200 operationally available warheads".^[281] As of 2016^[update], the UK had a stockpile of 215 warheads, of which 120 were operational.^[282]^[283] The 2010 Strategic Defence and Security Review reduced the number of warheads and missiles for the ballistic missile submarine on patrol to 40 and 8 respectively.^[284] Nuclear warheads from the Trident missiles are transported by road convoy several times a year from Coulport to Burghfield for refurbishment. Between 2000 and 2016, there were 180 accidents involving the vehicles, ranging from minor traffic accidents to a sudden total loss of power in one of the 44-tonne lorries that halted a convoy and caused a double lane closure and a tailback on the M6 motorway. The accidents have been more frequent in recent years.^[285]

The Trident system cost £12.6 billion to build (at 1996 prices) and £280m a year to maintain. Options for replacing Trident ranged from £5 billion for the missiles alone to £20 to £30 billion for missiles, submarines and research facilities. At a minimum, for the system to continue after around 2020, the missiles would need to be replaced.^[286] By 2016, the price of replacement of submarine had risen to £31 billion and it was estimated by Ministry of Defence that the cost of Trident replacement programme for 30 years would be £167 billion.^[287]

Trident renewal

With the tactical nuclear weapons having been withdrawn from service, Trident was the UK's only remaining nuclear weapons system.^[288] By this time, possession of nuclear weapons had become an important part of Britain's national identity. Not renewing Trident meant that Britain would become a non-nuclear power and strike at Britain's status as a great power.^[289] A decision on the renewal of Trident was made on 4 December 2006. Prime Minister Tony Blair told MPs it would be "unwise and dangerous" for the UK to give up its nuclear weapons. He outlined plans to spend up to £20bn on a new generation of ballistic missile submarines. The new boats would continue to carry the Trident II D-5 missiles, but submarine numbers might be cut from four to three, and the number of nuclear warheads would reduced by 20% to 160. He said although the Cold War had ended, the UK needed nuclear weapons, as no-one could be sure another nuclear threat would not emerge in the future.^[290]^[291]

The 2010 coalition government agreed "that the renewal of Trident should be scrutinised to ensure value for money. Liberal Democrats will continue to make the case for alternatives." Research and development work continued, but the final decision to proceed with building a replacement was scheduled for 2016, after the next election.^[292] There was already some urgency to move ahead because some experts predicted it could take 17 years to develop the replacement for the Vanguard-class submarines.^[293]^[294] The vote in the House of Commons on whether to replace the existing four Vanguard-class submarines was held on 18 July 2016.^[295] The Trident renewal programme motion passed with a significant majority with 472 MPs voting in favour and 117 against. The Leader of the Opposition, Jeremy Corbyn, and 47 other Labour MPs had voted against it; 41 did not vote but 140 Labour votes were cast in favour of the motion.^[296]^[297] The Successor class was officially named the Dreadnought class on 21 October 2016.^[298] The four new Dreadnought submarines were expected to come into operation in the early 2030s,^[299]^[300] with the programme lasting until at least the 2060s.^[301]

The government released a written statement on 25 February 2020, outlining that the UK nuclear warheads will be replaced and will match the US Trident II SLBM and related systems.^[302] The commander of the US Strategic Command, Admiral Charles A. Richard, told a US Senate hearing that the UK was already working to replace its warheads.^[303] The new UK warhead was planned to fit inside the future US Mk7 aeroshell that would house the future US W93 warhead. It would be the first UK-designed warhead in thirty years, since the Holbrook, an Anglicised version of the US W76. However, the US Congress was reluctant to authorise the US$32 million in funding for the first phase of design of the new aeroshell. Meanwhile, construction of the £634 million Pegasus enriched uranium facility was suspended in 2018, the £1,806 million Mensa warhead assembly facility was still under construction, and the proposed Hydrus facility for hydrodynamic weapons testing was cancelled in favour of using the French Teutates-Epur facility in Valduc.^[304]^[305]