Nassau Agreement

During the early part of the Second World War, Britain had a nuclear weapons project, codenamed Tube Alloys.[1] At the Quebec Conference in August 1943, the Prime Minister, Winston Churchill and the President of the United States, Franklin Roosevelt, signed the Quebec Agreement, which merged Tube Alloys with the American Manhattan Project to create a combined British, American and Canadian project.[2] The British Government trusted that the United States would continue to share nuclear technology, which it regarded as a joint discovery, after the war,[3] but the United States Atomic Energy Act of 1946 (McMahon Act) ended technical cooperation.[4]

Fearing a resurgence of United States isolationism, and Britain losing its great power status, the British Government restarted its own development effort,[5] now codenamed High Explosive Research.[6] The first British atomic bomb was tested in Operation Hurricane on 3 October 1952.[7][8] The subsequent British development of the hydrogen bomb, and a favourable international relations climate created by the Sputnik Crisis, led to the McMahon Act being amended in 1958, resulting in the restoration of the nuclear Special Relationship in the form of the 1958 US–UK Mutual Defence Agreement, which allowed Britain to acquire nuclear weapons systems from the United States.[9]

Avro Vulcan B.1A bomber

Britain's nuclear weapons armament was initially based on free-fall bombs delivered by the V-bombers of the Royal Air Force (RAF). With the development of the hydrogen bomb, a nuclear strike on the UK could kill most of the population and disrupt or destroy the political and military chains of command. The UK therefore adopted a counterforce strategy, targeting the airbases from which bombers could launch attacks on the UK, and knocking them out before they could do so.[10]

The possibility of the manned bomber becoming obsolete by the late 1960s in the face of improved air defences was foreseen.[10] One solution was the development of long-range missiles. In 1953, the Assistant Chief of the Air Staff (Operational Requirements), Air Vice-Marshal Geoffrey Tuttle, requested a specification for a ballistic missile with 3,700-kilometre (2,000 nmi) range,[11] and work commenced at the Royal Aircraft Establishment in Farnborough later that year.[12] In April 1955, the Commander-in-Chief of RAF Bomber Command, Air Chief Marshal Sir George Mills expressed his dissatisfaction with the counterforce strategy, and argued for a countervalue one that targeted administration and population centres for their deterrent effect.[10]

At a North Atlantic Treaty Organization (NATO) meeting in Paris in December 1953, United States Secretary of Defense, Charles E. Wilson, raised the possibility of a joint medium-range ballistic missile (MRBM) development programme. Talks were held in June 1954, resulting in the signing of an agreement on 12 August 1954.[13][11] The United Kingdom with United States support would develop an MRBM,[11][14] which was called Blue Streak.[13] It was initially estimated to cost £70 million (equivalent to £1.84 billion in 2019), with the United States paying 15 per cent.[15] By 1958, the project was in trouble. Its deployment was still years away, but the United States was supplying American-built Thor intermediate-range ballistic missiles under Project Emily, and there were concerns about liquid fuelled Blue Streak's vulnerability to a pre-emptive nuclear strike.[16][17]

To extend the effectiveness and operational life of the V-bombers, an Operational Requirement (OR.1132), was issued on 3 September 1954 for an air-launched, rocket-propelled standoff missile with a range of 190 kilometres (100 nmi) that could be launched from a V-bomber. This became Blue Steel. The Ministry of Supply placed a development contract with Avro in March 1956, and it entered service in December 1962.[18] By this time it was anticipated that even with Blue Steel, the air defences of the Soviet Union would soon improve to the extent that V-bombers might find it difficult to attack their targets, and there were calls for the development of the Blue Steel Mark II with a range of at least 1,100 kilometres (600 nmi).[19] Despite the name, this was a whole new missile, and not a development of Mark I.[20] The Minister of Aviation, Duncan Sandys, insisted that priority be accorded to getting the Mark I into service,[19] and the Mark II was cancelled at the end of 1959.[20]

A Skybolt missile at RAF Museum Cosford, showing the RAF roundel and the manufacturer (Douglas Aircraft) logo

Confronted with the same problem, the United States Air Force (USAF) also attempted to extend the operational life of its strategic bombers by developing a stand off missile, the AGM-28 Hound Dog.[21] The first production model was delivered to the Strategic Air Command (SAC) in December 1959. It carried a 4-megatonne-of-TNT (17 PJ) W28 warhead, and had a range of 1,189 kilometres (642 nmi) at high level and 630 kilometres; 390 miles (340 nmi) at low level. Its circular error probable (CEP) of over 1.9 kilometres (1 nmi) at full range was considered acceptable for a warhead of this size. A Boeing B-52 Stratofortress could carry two, but the underslung Pratt & Whitney J52 engine precluded its carriage by bombers with less underwing clearance like the Convair B-58 Hustler and the North American XB-70 Valkyrie. It entered service in large numbers, with 593 in service by 1963. Numbers declined thereafter to 308 in 1976, but it remained in service until 1977, when it was replaced by the AGM-69 SRAM.[22] Despite its being superior in performance to Blue Steel, the British showed little interest in Hound Dog. It could not be carried by the Handley Page Victor, and there were doubts as to whether even the Avro Vulcan had sufficient ground clearance.[23]

Even as Hound Dog was entering service, the USAF was contemplating a successor. An Advanced Air to Surface Missile (AASM) that could carry a 0.5-to-1.0-megatonne-of-TNT (2.1 to 4.2 PJ) warhead with a range of 1,900 to 2,800 kilometres (1,000 to 1,500 nmi) and a CEP of 910 metres (3,000 ft). Such a missile would make manned bombers competitive with Intercontinental Ballistic Missiles (ICBMs). However, it would also require significant technological advances. The missile became the AGM-48 Skybolt. As costs rose and support diminished, the USAF decreased its specifications to carrying a warhead 1,100 to 1,900 kilometres (600 to 1,000 nmi) and a CEP of 2.8 kilometres (1.5 nmi). This was estimated to cost $893.6 million (equivalent to $6.36 billion in 2021). A May 1960 report to the chairman of the President's Science Advisory Committee (PSAC), George Kistiakowsky, the PSAC Missile Advisory Panel stated that it was unconvinced of the Skybolt's merits, as the new LGM-30 Minuteman ICBM would be able to perform the same missions at much lower cost. PSAC therefore recommended in December 1960 that Skybolt be cancelled forthwith. United States Secretary of Defense Thomas S. Gates, Jr., elected not to request further funding for it, but avoided cancellation by reprogramming $70 million (equivalent to $498 million in 2021)from the previous year's allocation.[24]

A UGM-27 Polaris missile on the launch pad at the Cape Canaveral

A crucial reason for Skybolt's survival was the support it garnered from Britain.[24] Blue Streak was cancelled on 24 February 1960, subject to an adequate replacement being procured from the US. An initial solution appeared to be Skybolt, which combined the range of Blue Streak with the mobile basing of the Blue Steel, and was small enough that two could be carried on the Vulcan bomber.[25] Armed with a British Red Snow warhead, this would improve the capability of the UK's V-bomber force, and extend its useful life into the late 1960s and early 1970s.[26] Like the USAF, the RAF was concerned that ballistic missiles could eventually replace manned bombers.[27]

An institutional challenge came from the United States Navy, which was developing a submarine-launched ballistic missile (SLBM), the UGM-27 Polaris. The US Chief of Naval Operations, Admiral Arleigh Burke, kept the First Sea Lord, Lord Mountbatten, apprised of its development.[28] By moving the deterrent out to sea, Polaris offered the prospect of a deterrent that was invulnerable to a first strike, and thereby reduced the risk of a first strike on the British Isles, which would no longer be effective. It also had greater value as a deterrent, because retaliation could not be avoided. It would also restore the Royal Navy to its traditional role as the nation's first line of defence, although not everyone in the navy was on board with that idea.[29] The British Nuclear Deterrent Study Group (BNDSG) produced a study that argued that SLBM technology was as yet unproven, that Polaris would be expensive, and that given the time it would take to build the boats, it could not be deployed before the early 1970s.[30] The Cabinet Defence Committee approved the acquisition of Skybolt in February 1960.[31]

The Prime Minister, Harold Macmillan, met with President Dwight Eisenhower at Camp David near Washington 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 the Holy Loch in Scotland.[32] The financial arrangement was particularly favourable to Britain, as the US was charging only the unit cost of Skybolt, absorbing all the research and development costs.[26] Mountbatten was disappointed, as was Burke, who now had to face the possible survival of Skybolt at the Pentagon.[31] Exactly what was agreed with regard to Polaris was not clear; the Americans wanted any later offer of Polaris to be as part of a scheme for deployment of NATO MRBMs known as the Multilateral Force.[33] With the Skybolt agreement in hand, the Minister of Defence, Harold Watkinson, announced the cancellation of Blue Streak to the House of Commons on 13 April 1960.[25]

Skybolt proponents in the USAF hoped that the incoming Kennedy administration, which took office in January 1961, would be supportive of Skybolt, given its election campaigning on the basis of an alleged missile gap between Soviet and US capabilities.[34] Initially it was; Robert McNamara the new Secretary of Defense, defended Skybolt before the Senate Armed Services Committee.[35] He requested $347 million to purchase 92 Skybolt missiles in 1963, with the intention of deploying 1,150 missiles by 1967.[36] However, on 21 October 1961 the USAF raised its estimate of research and development costs to $492.6 million (equivalent to $3.51 billion in 2021), an increase of over $100 million (equivalent to $712 million in 2021), and production costs were now reckoned at $1.27 billion (equivalent to $9.04 billion in 2021), an increase of $591 million (equivalent to $4.21 billion in 2021).[37]

US Secretary of Defense Robert McNamara in 1967

The Kennedy Administration adopted a policy of opposition to independent British nuclear forces in April 1961.[38] In a speech at Ann Arbor, Michigan, on 16 June 1962, McNamara stated "limited nuclear capabilities, operating independently, are dangerous, expensive, prone to obsolescence and lacking in credibility as a deterrent," and that "relatively weak national nuclear forces with enemy cities as their targets are not likely to perform even the function of deterrence."[39] The former United States Secretary of State, Dean Acheson, was even more blunt; in a speech at West Point he stated: "Britain's attempt to play a separate power role – that is, a role apart from Europe, a role based on a 'special relationship' with the United States, a role based on being the head of a Commonwealth which has no political structure or unity or strength and enjoys a fragile and precarious economic relationship – this role is about played out."[40]

The Kennedy administration was concerned that a situation like the Suez Crisis might repeat itself, one that would once again incite a nuclear threat against the UK from the Soviet Union.[41] The Americans developed a plan to force the UK into the Multilateral Force concept, a dual key arrangement that would allow launch only if both parties agreed. If nuclear weapons were part of a multinational force, attacking them would require attacks on the other hosting countries as well. The US feared that otherwise other countries would want to follow the UK lead and develop their own deterrent forces, leading to a nuclear proliferation problem even among their own allies. If a deterrent was provided by an international force, the need for individual forces would be reduced.[42][43]

Between 1955 and 1960, the British economy had lagged behind that of the rest of Europe, growing at an average of 2.5 per cent per annum, compared with France's growth of 4.8 per cent, Germany's of 6.4 per cent, and the European Economic Community (EEC) average of 5.3 per cent, and Macmillan devoted much of 1960 to laying the ground for Britain's entry into the EEC.[44] The US was concerned that providing Polaris to Britain would jeopardise Britain's prospects of joining the EEC.[45] Long-term US policy was to persuade the UK to build up its conventional military forces, and to secure admission to the EEC.[46]

McNamara introduced cost-effectiveness analysis to defence procurement. Skybolt suffered from rising costs,[43] and the first five test launches were failures. This was not unusual; Polaris and Minuteman had similar problems.[47] What doomed Skybolt was an inability to demonstrate capability beyond that achievable by Hound Dog, Minuteman or Polaris.[43] This meant that there were few advantages for the United States in continuing Skybolt,[48] but at the same time its cancellation would be a powerful political tool for bringing the UK into their Multilateral Force.[43] The British, on the other hand, had cancelled all other projects to concentrate fully on Skybolt. When warned not to put all their eggs in the one basket, the British replied that there was "no other egg, and no other basket".[48] On 7 November 1962, McNamara met with Kennedy, and recommended that Skybolt be cancelled. He then briefed the British Ambassador to the United States, David Ormsby-Gore. Kennedy agreed to cancel Skybolt on 23 November 1962.[47]