Nuclear divergence between Britain and the United States: SDI and the Anti-Ballistic Missile Treaty

ABSTRACT This article draws on recently declassified documents on both sides of the Atlantic to reveal the depth of the disagreements between Britain and the United States over adherence to the Anti-Ballistic Missile (ABM) Treaty during the 1980s. In the context of the radical Strategic Defense Initiative (SDI), the Thatcher government feared that the dismissive attitude of the Reagan administration towards the ABM Treaty would undermine the role of arms control in providing mutual security and would have harmful consequences for the viability of Britain’s nuclear deterrent. Some British officials also suspected that the Reagan administration was manipulating alleged Soviet non-compliance with the Treaty as a pretext for abandoning it. The tensions between London and Washington on this issue were fundamental, as the Reagan administration perceived it as an obstacle which constrained the progress of SDI.


Introduction
The Strategic Defense Initiative (SDI), launched by President Ronald Reagan in a surprise speech on 23 March 1983, represented a seismic moment in both East-West relations and intra-Western relations.Reagan's speech talked of, 'rendering . . .nuclear weapons impotent and obsolete' and called for an end to the threat of nuclear retaliation as the basis of western strategy. 1He called for a shift to a multi-layered defensive system able to destroy incoming ballistic missiles in their boost, mid-phase and terminal stages of flight, in order to be able to protect the United States and its allies.The British government, led by Prime Minister Margaret Thatcher, faced the challenge of responding to an initiative that called into question some of its own assumptions about western security, risked upsetting the US-UK 'special relationship' and cast a shadow over the British nuclear deterrent.
This article draws on official documents that have been declassified in Britain during 2014 and 2015, as well as US documents released between 2007 and 2013.The British documents reveal the depth of the disagreement between London and Washington over adherence to the Anti-Ballistic Missile (ABM) Treaty.In particular, they point to the tensions between the Ministry of Defence (MoD) and Pentagon over the observance of arms control treaties.The US documents reveal the discomfort of Reagan officials over the stance taken by the Prime Minister herself who was influenced by the position taken by the MoD and the Foreign and Commonwealth Office (FCO).Those who have written on this topic, including Aldous, Cronin and Fitzgerald, have highlighted the Anglo-American antagonism over SDI but have neglected the crucial role played by the ABM Treaty in the British response. 2While Aldous and Fitzgerald refer to the disagreements between Britain and America over the ABM Treaty, these are presented as a marginal issue.This article fills a gap in the literature on the important differences between London and Washington over SDI.
This paper contends that the tensions between London and Washington over the ABM Treaty were fundamental, as the Reagan administration perceived it as an obstacle constraining the SDI's progress.As Freedman and Michaels have argued, SDI was interlinked with the future of arms control: as long as the ABM Treaty was honoured, it was not possible to proceed beyond the research stage with missile defence technologies. 3This article demonstrates how the acute concerns of the FCO and the MoD influenced the policy positions of the Prime Minister.
Both superpowers had invested considerable efforts in developing missile defence technologies in an attempt to escape the vulnerability of their home territories to massive nuclear destruction.Each came to recognise that missile defence could undermine strategic stability and lead them into a new domain of competition at colossal expense.The ABM Treaty emerged from the Strategic Arms Limitation Talks (SALT) after the Soviet leadership signalled its readiness to accept constraints on offensive and defensive weapons. 4aced by a US congress determined to prevent missile defence development, President Nixon decided to preserve a vestigial ABM deployment in return for the same limits on Soviet missile defences, while using it to place constraints on the Soviet offensive build-up.The Soviets accepted the US insistence that offensive systems be limited simultaneously with defensive systems.Yet, as this article points out, the Thatcher government's view of the ABM Treaty as an essential component of arms control and strategic stability, a view shared by many in the US security community, brought it into conflict with the Reagan administration.
The ABM Treaty limited the US and the Soviet Union to two anti-ballistic missile sites of up to 100 launchers each, one around the capitol and the other around a land-based missile facility.A further Protocol in 1974 reduced the deployments to a single location.It prohibited the development of space-based defences.The US deployed one missile field of interceptors at Grand Forks, North Dakota, but deactivated it after 1975, whilst the Soviets deployed the Galosh missile screen around Moscow.By signing the ABM Treaty, both sides committed themselves to abandoning comprehensive territorial missile defence systems.
SDI emerged in a period in which the United States was unsettled by the perception that the Soviet Union was enjoying a margin of nuclear superiority.In a letter to the Soviet President Leonid Brezhnev dated 22 September 1981, Reagan had expressed concern over, 'the USSR's unremitting and comprehensive military build-up over the past fifteen years, a build-up which in our view exceeds purely defensive requirements.'5Paradoxically, alongside the fear of Soviet superiority, there was also a growing consensus within the Reagan administration that it would be possible to confront and weaken the Soviet Union.This plan required the modernization of US nuclear and conventional forces to ensure that its military posture remained resolute.
It was in this context that the British accepted the need for US SDI research because they were aware that the Soviets were engaged in developing similar missile defence technologies.In the mid-1980s, the Soviets upgraded their A-35 Galosh missile defence system around Moscow with A-135, of which one type of interceptor was the Gazelle missile, and they also invested in missile defence research.Galosh and Gazelle were endo-and exo-atmospheric interceptors. 6he United States had also been working on a missile defence system of its own, the Homing Overlay Experiment (HOE) which predated SDI, designed to intercept missiles above the atmosphere. 7Mindful of Soviet research efforts, the US and Europe viewed Moscow's denunciations of SDI as hypocritical.President Reagan told Mrs Thatcher that the very concept of an agreement by which the two governments pledged to deprive their people of the right to defend themselves 'was an extraordinary one.'He added that the Soviet insistence on freezing SDI research was a cover for them to 'go ahead like crazy with their own missile defence plans.' 8 This article draws extensively upon documents from the UK National Archives, the Margaret Thatcher Foundation and the Reagan Library archive, supplementing them with individual memoirs.It utilizes this material to provide a richer and more nuanced understanding of US and UK differences, particularly over the ABM Treaty.Process tracing is employed in each of the key issue areas to uncover how their debates evolved in the period from 1983 to 1987.
The article begins by elucidating five aspects in which the UK differed conceptually from the Reagan administration over SDI, including nuclear deterrence, arms control and the perpetuation of the ABM Treaty.These are important because they demonstrate how, within an intimate Anglo-American relationship, there were fundamental differences over the nature of defence and the appropriate policies to be pursued towards Moscow.The article then proceeds, in sections two and three, to explain how the UK sought to constrain the US, by using the ABM Treaty to prevent testing and deployment of SDI systems and by opposing the argument that Soviet noncompliance absolved the US from arms control obligations.The final section analyses British fears concerning the impact of SDI on the future of their own nuclear deterrent.The conclusion discusses how Thatcher's attitude towards the ABM Treaty changed after she left office and how the challenge of nuclear proliferation led to the US withdrawal from the Treaty.

A British conception of deterrence, defence and arms control
The Reagan administration's unveiling of SDI laid bare significant differences between the US and Britain that went to the very heart of nuclear strategy and the role of arms control.The President regarded the strategy of Mutual Assured Destruction, in which nuclear war would result in devastation to both sides, as unethical.In his words it was ' . . . the craziest thing I ever heard of' and analogous to 'two spiders in a bottle locked in a suicidal fight . . .'9 President Reagan sought to change American strategy from the threat of the use of offensive weapons to one based around a comprehensive defence.American high technology would develop a shield that could prevent Soviet missiles from striking its territory.This was a policy that sought 'a great escape from the nuclear dilemma' and it presented a 'potent political argument' in its aspiration to defend the US population from nuclear destruction. 10Thatcher and Reagan were anxious about the public dismay over the nuclear arms race.Cronin suggests that Reagan may have been affected by the escalating discourse on nuclear weapons which could have encouraged his thinking on disarmament: 'Even SDI was proclaimed as the path to peace that so many were demanding.' 11he Thatcher government perceived things differently.It saw the East-West nuclear relationship as one that had evolved a considerable degree of shared understanding and predictability.The Prime Minister, the FCO and the MoD were united in the belief that the objective should be to maintain the threat of massive nuclear retaliation to an attack, thereby preserving mutual deterrence and preventing any risk of miscalculation.The Prime Minister believed that achieving a military balance was the key to security and in this she represented the nuclear orthodoxy. 12Although Reagan argued that SDI would reinforce deterrence, in fact he sought to transcend it. 13SDI would help to realise his ambition of making nuclear weapons obsolete.The British also feared that SDI might lead to short-term risks such as the Soviets attempting to strike pre-emptively before the US became invulnerable.Thus, Thatcher had said to Reagan in December 1984 at Camp David: We do not want our objective of increased security . . . to result in increased Soviet nuclear weapons.Nuclear weapons have served not only to prevent a nuclear war, but they have also given us forty years of unprecedented peace in Europe.It would be unwise . . . to abandon a deterrence system that has prevented both nuclear and conventional war. . . .The technological struggle goes on . . . .There are all sorts of decoys, jamming systems and technological developments such as making the missile boost phase even shorter.All these advances make crisis management more and more difficult.We have some real worries, especially about SDI's impact on deterrence. 14second source of conceptual divergence between the US and the UK was over the role of arms control.The Reagan administration saw SDI as capitalizing on US technological prowess over the Soviets by pressuring them on arms spending through space-based military competition.If the vulnerable Soviet economy was to avoid this pressure, it would have to acquiesce to US arms control demands, especially President Reagan's vision of eliminating nuclear weapons.At the November 1985 Summit in Geneva with Soviet General Secretary Mikhail Gorbachev, Reagan commented that, 'If he really wants an arms control agreement, it will only be because he wants to reduce the burden of defence spending that is stagnating the Soviet economy'. 15he Soviets had a number of reasons to fear SDI.Missile defences created uncertainty in their minds regarding the ability to strike strategic targets.They would have to compete on a new playing field of sophisticated, spacebased technologies, where the US had the upper hand.The Soviets also 11 Cronin, Global Rules, 157-8. 12Aldous, Reagan and Thatcher, 177-8. 13Freedman & Michaels, The Evolution of Nuclear Strategy, 519-21. 14 feared new breakthroughs that could exacerbate any disadvantage.There was therefore a risk that the Soviets would abandon arms control and try to saturate the missile defence by building up their offensive missile arsenal.There was a concern that they would turn to anti-satellite weapons (ASAT) in order to try and suppress SDI. 16or their part, the British were fearful that SDI would damage strategic stability and undermine their nuclear deterrent.The British position since 1972 had been to safeguard the ABM Treaty at all costs. 17The FCO continued to view it as 'the foundation of our present structure of deterrence.' 18 This was illustrated by a joint paper prepared by the MoD and the FCO in 1984 for the Prime Minister.The joint paper issued the following warning: Significant further BMD development would require wholesale changes in the present arms control regime.It would tend to undermine the 1972 ABM Treaty (important to East/West security), worsen wider East/West relations, harm the prospects for arms control in other areas, make the future of the NPT more precarious, and increase the danger of a new arms race . . .If the SDI provoked increased Soviet BMD deployments, there could be serious implications for the UK's national deterrent.Although these might be overcome by means of a countermeasures programme, BMD considerations may start to affect the domestic and political debate over Trident. 19 contrast, the Reagan administration exhibited a dismissive attitude towards the ABM Treaty.The US Defense Secretary, Caspar Weinberger, was a leading opponent of the Treaty, viewing it as flawed and arguing that the Soviets were violating it with impunity.Weinberger believed that by 1981, the Soviets were far ahead in efforts to secure strategic defence systems, particularly in their work on lasers.There was no doubt in his mind that the US would have to change the ABM Treaty in order to deploy SDI and the easiest solution was to provide notice of its intention to withdraw. 20he third point of divergence between the United States and the UK was over the credibility of SDI.Like many fellow scientists, Thatcher had doubts whether it would work. 21A separate concern was that SDI would be illequipped to counter the threat from aircraft or cruise missiles.Sir Percy Cradock, the Prime Minister's foreign affairs adviser, warned in a minute to Thatcher's foreign affairs private secretary, Charles Powell, that SDI was 'highly speculative', 'horrendously expensive' and 'highly destabilising in terms of the super power balance.'Cradock also pointed out that 'research and testing of a BMD system would eventually contravene the 1972 Anti-Ballistic Missile Treaty which is the foundation for our offensive-related deterrence.' 22 The fourth factor for the British was that a considerable degree of shared risk had evolved between the US and its European allies over its extended nuclear deterrent.Yet SDI introduced the prospect of the US homeland becoming invulnerable to attack, whilst Europe would remain vulnerable to short-range nuclear missiles as well as to conventional conflict.This created a potentially corrosive issue within the transatlantic relationship and imperilled the experience of shared vulnerability.From the outset, President Reagan's grand vision of missile defences was announced to the world without any advanced consultations with NATO capitals, thereby reinforcing the impression that US and allied interests were uncoordinated. 23 fifth area of divergence was over the implications of SDI for the UK's nuclear deterrent.If SDI was to augur a new era of superpower competition in missile defence, this could have a severe impact on the UK's minimum nuclear deterrent. 24Since the 1960s when the UK had begun to construct its own submarines to carry US Polaris missiles, it had been concerned by American and Soviet missile defences and it had undertaken the Chevaline programme to ensure that its warheads could penetrate Moscow's defences. 25British and French nuclear strategists had reason to fear that SDI would encourage the Soviets to build similar programmes which would render their nuclear deterrents obsolete. 26The British feared that the Soviet Union would be compelled to upgrade its ballistic missile defence system which would 'degrade and eventually nullify the British and French deterrents.' 27 Yet Britain had to tread warily on this issue because it wanted to preserve its intimacy with Washington and avoid a public disagreement.After all, the British government was in the process of acquiring the US Trident D5 missile. 28n each of these five ways, the UK found itself conceptually opposed to SDI.It appeared to Thatcher that the theology of nuclear deterrence was being questioned by its high priest and that Reagan had gone 'crazy'. 29evertheless, her political instincts and those of her government made them realise that outright denunciation of SDI risked harming British interests and would not stop the US scientific research programme.In these circumstances, Britain's policy towards SDI evolved incrementally and did not appear until after Thatcher's meeting with Reagan at Camp David in December 1984. 30here were three elements to the Prime Minister's strategy.Its first strand was to give declaratory support to SDI.One way of doing so was to express firm support for research into SDI technologies and authorise British firms to bid for lucrative research contracts. 31The second strand was for Thatcher to visit Washington to ensure that the administration adopted and upheld agreed positions in relation to the Soviet Union, such as ensuring that missile defences would not be deployed without further negotiations with Moscow.Thatcher tried to exert influence by emphasising her ideological affiliation with President Reagan.She sought to obtain assurances from the US relating to SDI and to prevent a US breakout from the existing arms control regime.The third strand was to prioritise the ABM Treaty and argue tirelessly for its preservation.

The Anti-Ballistic Missile Treaty as a constraint on US testing and deployment
If research on SDI proved successful, then the US did not want pre-existing arms control agreements to inhibit it from progressing towards deployment.There were those on the US side who sought a broad interpretation of the ABM Treaty that would permit the testing of new weapon technologies. 32In opposition to this, the UK believed that respect for the provisions of the ABM Treaty was sacrosanct.The British government lobbied the US administration, approaching officials that they considered sympathetic with their view, to make a commitment not to commence defensive programmes before a specified date.These efforts had some success partly because other European governments had also protested to Reagan. 33As well as the Soviet Union, America's allies were opposed to SDI and they too demanded that the United States adhere to the terms of the Treaty. 34rs Thatcher believed that if a stage was reached in which SDI production looked possible, there would be 'some serious and difficult decisions to make' which would have an impact on both the ABM Treaty and the 1967 Outer Space Treaty -the latter prohibiting the deployment of nuclear systems in space. 35Thatcher believed that the Soviet Union would respond to SDI by either developing their own strategic defence system or saturating it with offensive missiles.She was therefore unconvinced of the rationale to deploy SDI when it could be defeated by other means. 36t Camp David in December 1984, she extracted from the President a fourpoint agreement on the way forward for SDI.First, the principal aim of the US and the West would not be to achieve nuclear superiority over the Soviet Union but to maintain a strategic balance.Second, the deployment and production of SDI systems would be a matter of negotiation between the superpowers, whilst abiding by treaty obligations.This was essential in British eyes to prevent SDI research leading to deployments that would undermine the ABM Treaty.Third, the overall aim would be to enhance deterrence rather than to supplant it.Fourth, East-West negotiations would work to achieve security with reduced levels of offensive systems on both sides. 37revious scholarship relating to the Camp David meeting has emphasised Thatcher's concerns over three issues: Reagan's ambition to abolish nuclear weapons, US attitudes towards nuclear deterrence and Britain being left out of the debate. 38These were certainly important factors, but the literature has neglected the fundamental differences between Thatcher and Reagan over the implications of SDI for the fate of the ABM Treaty and the resulting adverse implications for crisis management.The outcome of Camp David was seen in London as a success, but caused upset in Washington. 39Howe described it as going 'a long way towards drawing the most disturbing teeth of the SDI programme.' 40hatcher's position on the ABM Treaty was likely influenced by the advice she was getting from the FCO.In the period after the unveiling of SDI, she had argued that the Treaty did not place restrictions on SDI research.John Weston, head of the FCO Defence Department, had advised her that SDI research could not advance to the development phase without testing, and this was clearly restricted by the ABM Treaty.Weston believed that the Prime Minister had taken his advice on board, reflected in the position she started taking from the moment she met with President Reagan in December 1984. 41owever, this did not mark the end of US efforts to stretch the interpretation of the ABM Treaty.The US did not abide by the four points agreed at Camp David, as Britain had hoped, and the differences between the two sides intensified over the next two years.During the early months of 1985, there was growing concern within the FCO over how SDI could undermine the ABM 36  Treaty.In a press conference in Washington on 21 February, Thatcher had emphasized that many years would have to elapse between the commencement of research on SDI and the actual deployment of missile defences.Yet the comments of the Director of the SDI Organization, General James Abrahamson, contradicted this assertion when he stated that the schedule for the testing in space of tracking and targeting systems against missiles had been brought forward to 1987.While Abrahamson had reassured NATO allies that testing under the SDI programme would be carried out in conformity with the ABM Treaty, the FCO expressed its concerns over the Reagan administration's attitudes towards the Treaty: Some US officials have begun to argue that field testing of SDI-related technologies is permissible under the Treaty, on the grounds that these are not solely applicable to BMD purposes and do not constitute stand-alone substitutes for an existing or deployable ABM system.There is a clear possibility that such arguments will increasingly be used to justify steps along the BMD road that appear to run counter to President Reagan's repeated assertion that the SDI involved only research, as permitted under the ABM Treaty . . . .Piecemeal activities relevant to the grey areas of the treaty could risk undoing its central provisions much sooner than would otherwise be expected. 42we saw the need to address the issue with US officials at the earliest opportunity in order to reach a common position on an interpretation of the ambiguities in the ABM Treaty. 43ritain expressed strong opposition to those in the Reagan administration who sought to reinterpret the limits of the ABM Treaty to accommodate SDI.Up to 1985 the Treaty was interpreted as prohibiting anything other than research on ballistic missile defences, except for fixed land-based systems.The revised interpretation favoured by the Reagan administration would have allowed development and testing to proceed on strategic defences based on 'new physical principles.' 44 From a US perspective, 'Agreed Statement D' in the Treaty allowed for testing and development of ABM systems based on 'other physical principles' than those known when negotiations were taking place in 1972.SDI was based upon these new ideas.Reagan officials believed that the broader interpretation presented in Agreed Statement D applied to the research undertaken as part of SDI. 45 The British saw this as an attempt to facilitate testing of exotic new technologies such as x-ray lasers and particle beam weapons.The FCO believed that testing SDI technologies, such as a space-based x-ray laser, would violate both the ABM Treaty and the Outer Space Treaty. 46he ABM Treaty also prohibited interference with satellites that were used for the monitoring of arms control agreements.During the Cold War, successive US administrations had refrained from seeking a military strategic advantage over the Soviets in ASAT programmes.The Reagan administration, however, was the exception and feared that Soviet ASAT technology might disable parts of the SDI architecture. 47The US also saw potential in developing potential SDI weapons technologies under the guise of anti-satellite projects. 48The British made clear their opposition to these approaches.Mrs Thatcher told the US President that the British and American public needed to be reassured that SDI was only a research programme.If the development stage was reached, alternative options would have to be considered including the renegotiation of the ABM Treaty. 49Evidence that UK and US paths were diverging was provided by the outspoken attack by Foreign Secretary Geoffrey Howe on SDI at the Royal United Services Institute in March 1985.He warned that SDI risked destabilizing the superpower strategic relationship and cautioned that 'there would be no advantage in creating a new Maginot Line of the 21st century liable to be outflanked by relatively simpler and demonstrably cheaper countermeasures.' 50The Times newspaper responded by stating that 'the SDI now threatens to become the focus of one of the most serious rifts in the Atlantic Alliance since its inception', at a time when the Soviet Union was seeking to achieve its cherished goal of decoupling the transatlantic relationship. 51The riposte by Assistant Secretary of Defence for International Security Policy, Richard Perle, when he visited London left no doubt that the US administration had been angered by Howe's remarks. 52ldous claims that 'Howe had been offered up as a patsy' in the wake of the US anger over his RUSI speech.In reality, Thatcher agreed with much of what he said but felt that his criticisms had been too blunt. 53ritain was not alone in its strong reaction to the apparent US shift in position over the ABM Treaty.West German Chancellor, Helmut Kohl, believed that the US had made a major political blunder.Although Secretary of State George Shultz believed that the broader interpretation of the ABM Treaty was legitimate, he was concerned about the impact on US allies.In a speech to NATO in October 1985, Shultz made it clear that SDI deployment would be carried out in close coordination with US allies and negotiated with the Soviets in accordance with the terms of the ABM Treaty. 54n the course of 1986, the Thatcher government stepped up its efforts to influence the direction of SDI policy.Howe met with US arms control negotiator Paul Nitze on 4 March to emphasize the importance of preserving the ABM Treaty, and urged the US to adhere to its restrictive interpretation. 55hatcher had suggested to Nitze that he could do as she and the President had done at Camp David: 'sit down with the Soviets and show how this would all be negotiated in the context of the ABM Treaty . . .' 56 There was unease within the US administration over a 'disturbing' letter that Thatcher sent to the President in February 1986. 57In the letter, she warned that the Soviets were using SDI to try to undermine Alliance cohesion and that missile defences were viewed as a block to nuclear reductions.In her view, it was no less important for the Reagan administration to assuage Soviet fears and reassure Moscow against 'a sudden and unforeseen break-out' in the realm of missile defence. 58Thatcher called on Reagan to offer the Soviets more information on the future scope and timescale of the SDI's development, and proposed a timeframe for reductions in offensive weapons.She advocated an arrangement that would extend, refine and strengthen the ABM Treaty in return for offensive force reductions and a commitment not to carry out particular defensive programmes before a stipulated date. 59n the Reagan administration's critique of Thatcher's letter, it was noted that 'there was a disturbing correlation' between perspectives offered by certain elements within the US government, which had been repeatedly rejected, and the option being proposed by Mrs Thatcher. 60The reference here was to Nitze who was viewed as the fiercest opponent of SDI within the State Department, and who had argued to stop the initiative because of its adverse impact on arms control efforts with Moscow. 61It was 'a bit worrisome' that Thatcher's position of linking ABM extension to nuclear reductions was almost identical to the stance that Nitze had taken with little success to date.The critique continued: The PM's [Thatcher's] position is very understandable from the UK point of view.The bottom line, however, is that the option suggested by the PM does put the priority on achieving reductions in strategic forces and protecting the public support for current strategy (both elements related to the UK Trident issue).It does not maximize protection for achieving the promise of SDI, but rather protects the SDI research program as a lever for ensuring reductions and a hedge against Soviet breakout.The President's policy, however, does not share these priorities -it places the pursuit of the promise of SDI as a fundamental element of our long term strategy and essential to future national security -and we fear that even a viable SDI research program could not long survive in the context that would be provided by the PM's alternative. 62 the Reykjavik summit with Gorbachev in October 1986, Reagan refused to confine SDI research to the laboratory.This issue stood in the way of a US-Soviet agreement on reducing or even abolishing ballistic missiles.Thatcher was so worried by this radical departure in the US nuclear stance that she crossed the Atlantic to discuss the matter. 63As well as gaining a reaffirmation of the importance of 'effective nuclear deterrents based upon a mix of systems', and a US commitment to modernizing Britain's nuclear deterrent, she obtained an assurance that the SDI research programme would proceed in accordance with the ABM Treaty. 64This promise was designed to reassure Europe and prevent de-coupling in transatlantic security.It reduced the risk of a crisis developing and made it harder for America to unilaterally abrogate the ABM Treaty.
Following the Reykjavik meeting, the salience of the SDI debate declined.It was overtaken by the negotiations over theatre nuclear forces and the Soviet acceptance of the radical 'double-zero' proposal, that envisaged no deployment of western weapons on the condition that the Soviets withdrew their currently deployed systems.Nevertheless, in the period up to Reykjavik, alongside the US Congress which had fought for the right to interpret treaties, the British government also played a role in holding the US successfully to a narrow interpretation of the ABM Treaty as a means to constrain the development of SDI.

Fears of Soviet activities justifying US non-compliance
Croft has identified so-called strategic 'conservatives' and 'fundamentalists' within the Reagan administration whom the British government suspected were hostile towards arms control with the Soviet Union. 65There were those in the US government who believed that Moscow was cheating on its arms control commitments and who advocated strategic superiority as the only reliable policy.SDI offered a means, through the development of advanced 62 RRL, Linhard Collection, RAC Box 9, Critique of PM Thatcher's 11 Feb.Letter. 63Aldous, Reagan and Thatcher, 218-21. 64Margaret Thatcher, The Downing Street Years (London: Harper Collins 1993), 473. 65Croft, The United States and Ballistic Missile Defence, 2. military technologies, to force the Soviet Union into a competition that would sap its strength. 66Figures such as Richard Perle had argued that the ABM Treaty 'was a mistake in 1972 and the sooner we face up to the implications of recognizing that mistake the better.' 67 Thus Reagan administration officials were arguing that the United States was justified in pressing forward with measures that contravened its treaty obligations. 68The British government advocated restraint and pointed to the Camp David agreement where Reagan had affirmed that SDI developments would remain compliant with the ABM Treaty.Aldous has claimed that Thatcher exploited the divisions between Weinberger and Shultz over SDI in furtherance of these aims. 69Yet a review of declassified papers pertaining to Thatcher's meeting with Reagan and Shultz in December 1984 as well as his own memoirs reveal that the Secretary of State shared Reagan and Weinberger's concerns over Soviet superiority.Moreover, the Prime Minister's foreign affairs adviser believed that Shultz was on the same page as Weinberger in regard to withdrawal from the ABM Treaty.Powell advised the Prime Minister that Shultz in tandem with Weinberger was 'canvassing the possibility of US withdrawal from the ABM Treaty.' 70 Shultz believed that the Krasnoyarsk large phased array radar which the Soviets were constructing 'could serve a battle management' function and had 'vast political consequences.'If the Soviets were violating the terms of agreements reached years ago, how could the United States expect Moscow to honour future agreements? 71uring the discussions at Camp David in December 1984, Shultz insisted that the Soviets were devoting considerable resources towards the development of defensive systems, alleging that the radar facility under construction at Krasnoyarsk violated the ABM Treaty.He added that Moscow was well positioned to break out from the conditions imposed by treaties, and that their emphasis on defensive systems had put the US at a disadvantage.The SDI research was designed to contribute to enhancing deterrence and strengthening the US position.Shultz argued that the US could not just sit back and let the Soviets build up a significant advantage in defensive systems. 72Unlike Weinberger, Shultz sought to lower the noise surrounding the Krasnoyarsk radar while telling the Soviets that their treaty violations needed to be rectified. 73reedman and Michaels describe the Krasnoyarsk radar as 'an unusually clear case of a Soviet violation' of the ABM Treaty. 74Soviet Foreign Minister Eduard Shevardnadze admitted in October 1989 that the radar had indeed violated the terms of the Treaty. 75Whilst the initial strategy of the administration was to use the Krasnoyarsk facility to justify abandoning the Treaty, this was later changed.Instead, the Reagan administration sought to promote SDI by reinterpreting its provisions. 76lear tensions emerged between Weinberger and British Defence Secretary Michael Heseltine.In February 1985, Heseltine told Weinberger that SDI was 'likely to create severe transatlantic strains in the coming months and years.' 77 Heseltine believed that the American accusation of Soviet cheating over Krasnoyarsk was a false pretext to prepare NATO for the deployment of defensive systems.In a revealing minute to the Prime Minister, Heseltine wrote: This [the American accusation] placed me in a difficult position because, as the Americans know, our expert advice is that it is not possible on the current evidence to determine whether or not the radar contravenes the ABM Treaty. . . .Moreover, we had to bear in mind the link with the US modernisation of BMEWs facilities at Fylingdales . . ..where we could face charges from the Russians of a breach by the Americans of the 1972 Treaty . . . . . ..It seemed unnecessary to muddy the waters by bringing in disputed violations by the Soviet Union of the ABM Treaty itself.These arguments were not at all well received by Mr Weinberger and his team.They were dismissive of our reservations about whether a violation had been established almost to the point of arguing that they were the only people capable of reaching a judgment. . . .They were determined to obtain a statement on behalf of the Alliance as a whole deploring Soviet violations.Based upon these discussions over the wording of the Communique itself, my own suspicion was that the Americans see it as an important plan in preparing the Alliance for the deployment of defensive systems to establish clearly in public a record of Soviet violations, coupled with the risk of a Soviet "break-out" from the ABM Treaty. 78seltine's displeasure was reinforced by the sense that Weinberger discounted his views and those of his scientific advisers.' 79Heseltine did not accept the US perspective that the Russians were ahead in the game or that they were cheating, so there was therefore little justification to develop more effective systems to get ahead of them.
The rising tensions between Britain and the US over the ABM Treaty were reflected in a private conversation between Shultz and the UK Permanent Under-Secretary of State, Sir Antony Acland, on 25 October 1985.Shultz told Acland that Weinberger had very strong views on the Soviet violation of the ABM Treaty, especially in regard to the Krasnoyarsk radar.He expressed concern that whatever the private British interpretations of Soviet violations of the Treaty might be, 'there should be no public divergence of view' over the matter. 80he ballistic missile early warning system (BMEWS) facility at Fylingdales in Yorkshire encapsulated the risks and opportunities that Britain faced.As Heseltine's minute made clear, the British were concerned that US plans to modernize Fylingdales could be perceived by the Soviets as a violation of arms control commitments, just as the Americans were accusing the Russians over the Krasnoyarsk radar.Heseltine told Weinberger that the modernization of Fylingdales would come at a political cost.Britain would have difficulties in making the case that the early warning system did not violate the ABM Treaty even though he knew that the facility complied with the Treaty.Heseltine also mentioned having to confront political criticism from the Labour opposition that SDI and the early warning system served US interests and not those of Britain. 81Four days later, Thatcher pointed out to Weinberger that any work on Fylingdales would need to be described as 'modernization', rather than the installation of a new system. 82This demonstrated that the UK was aware that the construction of the radar could be seen as a violation of the Treaty.The British were in a difficult position because the US radar was based on UK soil: it was hosting a US asset that did not protect British territory, but which could nevertheless make it a target. 83he FCO took the view that the modernisation of Fylingdales would be consistent with the terms of the ABM Treaty because, unlike Krasnoyarsk, it was already in being.In fact, there was a good argument that the Fylingdales radar did not comply with the ABM Treaty.While the Treaty allowed for modernization of existing radars, the Fylingdales site was to receive a new three-faced 360-degree-coverage large phased-array radar as part of the upgrade. 84Moreover, there was the deeper problem that approving the modernization could be seen as drawing Britain closer to approving US missile defence deployments.During 1985, Britain was reluctant to approve the modernization work and had called on the SDI Organization to ensure that those designing the ballistic missile defence infrastructure should be instructed not to include a role for Fylingdales in any US missile defence plans.The US provided assurances to Britain on this request. 85Fylingdales was upgraded finally between 1989 and 1992. 86rs Thatcher was fearful that if the US reneged on one agreement it would risk undermining the entire Cold War arms control regime.At a meeting of NATO leaders in November 1985, the British Prime Minister said to Reagan that 'she was very pleased to hear that the United States would continue to abide by the ABM Treaty and planned to respect the SALT II Agreement.' 87This message was reinforced by Howe when he told US representatives at a NATO ministerial meeting that the ABM Treaty should be strengthened and SDI not allowed to block arms control. 88evertheless, in the course of a phone conversation with Thatcher the following year in the wake of the Reykjavik Summit, President Reagan spoke dismissively of the ABM Treaty and made it clear that he viewed it as an obstacle to US strategic policy.Once again, the British government had been successful in holding the US administration to its arms control agreements.In particular, efforts by the administration to argue that alleged Soviet violations of the ABM Treaty justified US non-compliance, were resisted by London.

The implications of SDI for the British nuclear deterrent
A further factor that weighed on British minds in relation to SDI was its implications for the British nuclear deterrent.American pressure to deploy SDI technologies threatened their withdrawal from arms control agreements that underpinned the structure of the existing military balance.Britain could find its own deterrent rendered outdated by developments in weapons technology. 89The development of missile defences by both superpowers put in doubt the credibility of the minimal nuclear systems possessed by the UK and France.Days after Reagan's SDI speech of March 1983, British defence officials issued the following warning to Number Ten: Any liberal interpretation of the existing [ABM] Treaty by the Soviet Union, matching US advances, or renegotiation of the Treaty, could have profound consequences for the credibility of the British independent strategic nuclear deterrent.The effectiveness of the independent nuclear force depends on a policy shared by the two superpowers of deterrence rather than defence.It remains in our interest to ensure that deterrence can be achieved at a minimum 85 Taylor, Britain's Response to the Strategic Defence Initiative, 230. 86Stocker, Britain and Ballistic Missile Defence, 95. 87 RRL, Linhard Files (Folder: Geneva Summit Records, Nov 19-21 1985 [4 of 4]) OA 92178. 88Taylor, Britain's Response to the Strategic Defence Initiative, 229. 89Adelman, Reagan at Reykjavik, 154-5.
cost and we would therefore wish to oppose strongly any change in the current status of operational ABM systems. 90itain was concerned that the possible demise of the ABM Treaty could lead the superpowers to deploy extensive missile defences that would negate the British deterrent.Once the US was ready to deploy missile defences, the Russians could improve their own ABM systems and the UK's ability to threaten Moscow would be weakened.Heseltine was fearful that a Soviet missile defence system designed to counter the US would undermine the rationale for Britain's future Trident system. 91If the United States were to decouple itself from NATO, Britain would effectively be defenceless with an inoperable nuclear deterrent. 92Towards the end of 1985, such concerns would have been fuelled by reports from Britain's Embassy in Moscow that the Soviet military was threatening to develop space-based defences in response to SDI. 93 In a minute to Powell, Howe's private secretary Len Appleyard had written of the Foreign Secretary's 'strong conviction that we must continue to avoid giving the impression that we see a nuclear-free world as realistic or desirable, either as an objective in itself or as part of the rationale for the SDI.' 94 However, during the autumn of 1986, there was further concern from the Thatcher government regarding the intentions of the Reagan administration over arms control.Acland sent a telegram to the FCO, in which he presented 'a disturbing insight into right-wing attitudes on arms control.' 95 Acland noted that 'it came out very clearly that Weinberger is not yet reconciled to the concessions (no SDI deployment for at least seven and a half years).'Moreover, during Howe's meeting at the Pentagon with Weinberger and Perle on 9 September 1986, they were irritated when he stressed the importance for the allies of the United States continuing the restrictive interpretation of the ABM Treaty and asked whether there had been any discussion of the extension of the ABM Treaty withdrawal period or the codification of the restrictive interpretation.Weinberger and Perle were insistent that there could be no such discussion or codification.They claimed that the SDI programme was already being conducted in accordance with the restrictive interpretation and that negotiated constraints on SDI were unacceptable.Nitze strongly opposed Weinberger's apparent interest in deployment in space which he described as a violation of the ABM Treaty.He believed that Weinberger 'simply wanted to break the ABM Treaty.' Weinberger wanted the President to announce a phased SDI deployment in February 1987 and to state publicly that a broad interpretation of the ABM Treaty would make this permissible. 97On 20 September 1987, the Senate Foreign Relations Committee declared that the Reagan administration's reinterpretation of the ABM Treaty to allow the deployment of missile defences was 'the most flagrant abuse of the Constitution's treaty power in 200 years of American history.' 98 Yet the British concerns over SDI dissipated towards the end of the Reagan era with a commensurate decline in anxiety over the risk to the British deterrent.Thatcher was aware how much SDI meant to President Reagan and came to see it as a blessing when the determination to preserve it prevented him from signing up to abolish nuclear weapons at his Reykjavik summit with President Gorbachev. 99urthermore, the UK saw advantages in securing research contracts for its own industries from a programme estimated to be worth 26 USD billion.Thatcher viewed British participation in SDI as a means to enhance the Anglo-American relationship, especially through collaboration in sensitive areas of defence, but also as a pathway to strengthen Britain's standing commercially and technologically.Officials in the Reagan administration were only too happy to oblige.Weinberger, for example, told the Prime Minister that the United States 'wanted a special role' for Britain in the research project and had even drawn up a number of areas where he felt Britain had a special contribution to make.A gratified Thatcher responded that Britain's record as an ally, its history of unique defence cooperation in sensitive areas and its scientific and technical expertise meant that it was entitled to special consideration and a considerable share of the research work. 100A Memorandum of Understanding (MoU) with the United States was signed on 6 December 1985 but it did not guarantee a proportion of research to the UK as Thatcher had wanted. 101ver time the Reagan administration's commitment to SDI became effectively qualified amid promises to share the technology with allies and adversaries alike.The Soviets were also aware that although Reagan was personally awestruck by the prospects of strategic defence, many others within the US government were 96 Ibid. 97Shultz, Turmoil and Triumph, 871. 98 not.After 1986 there was growing opposition from a Congress that was controlled by the Democrats and which cut funding for the programme. 102Furthermore, the USSR became less worried by SDI as they recognised it could be countered with simple and effective countermeasures. 103Opposition to SDI was no longer a Soviet priority.This helped to switch Soviet attention away from missile defence and paved the way for the signing of the Intermediate range Nuclear Forces (INF) Treaty at the Washington summit in December 1987. 104

Conclusion
Previous scholarship has understated the importance of the ABM Treaty in Britain's reaction to SDI, but this article has sought to redress that perspective.The Treaty was central to Britain's response and a 'pivot(al)' issue in the missile defence and SDI debate. 105The UK government regarded the role of the ABM Treaty as essential in preserving a concept of deterrence based upon the threat of nuclear retaliation, believing this to be the key to stability and to safeguarding the UK's nuclear deterrent.Britain saw the Treaty as preventing the US from transitioning from research into new SDI technologies, testing and deployment.They resisted US efforts to manipulate alleged Soviet non-compliance with the Treaty as justification for abandoning it.The British feared that US derogation from the ABM Treaty would end the role of arms control in providing mutual security, with knock-on consequences for Britain's nuclear deterrent.The literature on the dialogue between Britain and the United States over SDI has neglected the role Britain played in attempting to constrain it through its emphasis on the need to preserve the ABM Treaty at all costs.
This article has demonstrated that despite being the junior partner in the special relationship, the British were able to exert meaningful influence upon America's strategic nuclear policy towards the Soviet Union.Britain offered carefully calibrated support for SDI, aware that it was walking a fine line in preserving its relationship with Washington, whilst holding the US to its arms control commitments.The Camp David four points of December 1984 and the speech of Foreign Secretary Howe a year later encapsulated the British position towards SDI.The British preference was for SDI to be negotiated away as part of an arms control framework that reduced the number of offensive missiles. 106At the same time, the Thatcher government was determined to safeguard the ABM Treaty as the foundation stone of superpower arms control.Although the contentious nature of SDI diminished after the Reykjavik summit, the issue of missile defence did not disappear.
The great irony is that Thatcher became a fierce critic of the ABM Treaty in the years after she left Number Ten.In her 2002 book, Statecraft, she describes it as a 'Cold War relic' and 'the arms control treaty that undoubtedly does most harm and makes least sense.' 107 The former Prime Minister accepted that the Treaty 'had some rationale when it was signed in 1972, though in retrospect not much.' 108Contrary to what she asserts in Statecraft, this paper has demonstrated that the Prime Minister was in fact closely aligned with the position of the FCO and the MoD on the need for adherence to the ABM Treaty during the Cold War.
What changed in the post-Cold War period was the justification for missile defence: it became less about superpower relations and much more concerned with the threat posed by nuclear proliferation.President Clinton authorised negotiations with the Russian government to search for ways to amend the ABM Treaty to allow a limited defence of the US from a 'rogue' nation attack. 109ut it was under his successor, President George W. Bush, that the US decided to withdraw from the Treaty and announced its intention in December 2001.A year later President Bush proclaimed that the US would deploy anti-ballistic missiles in Alaska as part of a national defence system.The withdrawal from the ABM Treaty was eventually realized nearly twenty years later.By that stage the nuclear debate had moved on and the United States had become focused on meeting the threat from states newly acquiring nuclear weapons.
[Ronald Reagan Library, hereafter RRL] Kraemer Collection, Box 90718, White House Memorandum of Conversation: Meeting with British Prime Minister Margaret Thatcher, 28 December 1984. 15Paul Lettow, Ronald Reagan and his Quest to Abolish Nuclear Weapons (NY Random House 2005), 174.
Prados, 'The Strategic Defence Initiative: Between Strategy, Diplomacy and US Intelligence Estimates', 89.