The decision to expand the UK’s nuclear weapons stockpile by 40 per cent was slipped onto page 76 of the government’s Integrated Review of Security, Defence, Development and Foreign Policy in March. The only reason to announce a major strategic decision in such a quiet way is to avoid attention, which is exactly what happened. The UK is now committed to maintaining a larger stock of nuclear warheads than China (according to US estimates) and there has been too little scrutiny of the policy.

One organisation that hasn’t ignored it is the Campaign for Nuclear Disarmament. CND commissioned Christine Chinkin and Louise Arimatsu of the LSE to provide a legal opinion on whether UK policy is in breach of Article VI of the Non-Proliferation Treaty, which requires that signatories take effective measures ‘in good faith’ towards nuclear disarmament. Chinkin and Arimatsu argued that it is. CND plans to report the UK to the UN at the next NPT Review Conference, repeatedly postponed since the start of the pandemic and currently scheduled ‘to be held no later than February 2022’.

Between 2010 and 2019, successive Conservative governments held Britain up as a principled supporter of disarmament, pointing to ‘step by step’ reductions in the UK nuclear stockpile since 1980. In 1998 it was nominally capped at 200 warheads though 225 in fact remained. In 2010 and 2015 the UK said it was committed to reducing the stockpile to 180 warheads. Lifting the cap to 260 this year was a volte-face into open illegality, justified by unspecified ‘technological and doctrinal threats’. The plan is still unclear: what will become of the warheads awaiting decommissioning at the Royal Naval Armaments Depot in Coulport? Is the work of nuclear decommissioners at Burghfield to stop, or will the stockpile be filled over time with new bombs?

The defence intelligentsia is divided over the reason for a larger nuclear stockpile. One argument is that it would allow for the deployment of low-yield ‘tactical’ nuclear weapons, which the UK has not had since the 1990s. The country’s first nuclear weapons, from ‘Blue Danube’ to ‘Red Beard’, were smaller yield atomic bombs designed to be delivered from the air. But since the 1960s the UK’s nuclear programme has been based on submarine-launched ballistic missiles (first Polaris, now Trident). The missiles are leased from the United States. The warheads are made in the UK, but using rebranded American designs. The US kept tactical nuclear weapons in the UK, at RAF Lakenheath, until 2006. There are no known British plans for the procurement of tactical nuclear weapons.

Lawrence Freedman has argued that raising the stockpile cap to 260 would allow for two fully armed Vanguard nuclear submarines to be on patrol at once (each submarine can load sixteen missiles, each of which carries eight warheads, for a total of 256 on two submarines). But the strategic need for this is unclear.

The Integrated Review included the standard rationale for having a ‘nuclear deterrent’ (even though what the UK has is nuclear weapons; deterrence is a conceptual matter): the weapons are to be used in ‘extreme circumstances of self-defence’, and not for threatening non-nuclear states so long as they are not in breach of the NPT. But the Integrated Review also included a striking revision to British policy. Under the new policy the UK ‘reserves the right to review’ its assurances not to use nuclear weapons against non-nuclear states ‘if the future threat of weapons of mass destruction, such as chemical and biological capabilities, or emerging technologies that could have a comparable impact, makes it necessary’. This could be read as opening the door to the use of nuclear weapons in response to a non-nuclear attack, crossing the line from ambiguity to recklessness.

CND’s argument that the UK is breaking international law is a necessary challenge to the government, but it is not sufficient. There is no reason to confine a critique of British nuclear policy to the limited strictures of international law, themselves often a weapon of the strong. Political critiques from pragmatism, from hypocrisy, from strategy and from principle are needed. The UK has unilaterally committed to a larger nuclear weapons stockpile and a more aggressive nuclear weapons doctrine, and vague references to ‘the prevailing security environment’ were all the cover the government needed.