Policy paper

UK nuclear deterrence: what you need to know

Updated 24 March 2016

UK and nuclear disarmament

  • as a responsible nuclear weapon state and party to the Treaty on the Non Proliferation of Nuclear Weapons (NPT), the UK also remains committed to the long term goal of a world without nuclear weapons

  • we have reduced our own nuclear forces by over half from their Cold War peak in the late 1970s

  • we are the only nuclear weapon State recognised under the NPT which has reduced its deterrent capability to a single nuclear weapon system; We have dismantled our maritime tactical nuclear capability and the RAF’s WE177 free fall bombs

  • as a result of our reassessment of the minimum necessary requirements for credible deterrence, since 2010 we have:
    • reduced the number of warheads onboard each submarine from 48 to 40
    • reduced our requirement for operationally available warheads from fewer than 160 to no more than 120
    • reduced the number of operational missiles on each submarine to not more than 8
    • by the mid-2020s, we will reduce the overall nuclear weapon stockpile to no more than 180 warheads, meeting the commitments set out in the 2010 Strategy and Strategic Defence and Security Review (SDSR)
  • of the recognised ‘nuclear weapons states’ (NWS), we possess only approximately 1% of the total global stockpile of nuclear weapons, the smallest of all the NPT nuclear weapon states

  • our submarines on patrol are at several days’ notice to fire and, since 1994, we do not target our missiles at any state

  • the UK plays a leading role on disarmament verification with the US and Norway

Infographic: UK’s leading role in multilateral nuclear disarmament

Infographic: UK's leading role in multilateral nuclear disarmament. Crown Copyright
Crown Copyright.

The infographic shows UK operational warheads reducing from 160 in 2010 to 120 in 2015 and operational warheads on patrol reducing from 48 in 2010 to 40 in 2015.

An independent deterrent

  • since 1969, the Royal Navy has delivered the nuclear deterrent under Operation Relentless, with at least 1 of 4 nuclear armed submarines on patrol at all times

  • our retention of an independent centre of nuclear decision making makes clear to any adversary that the costs of an attack on UK vital interests will outweigh any benefits

  • decision making and use of the system remains entirely sovereign to the UK; only the Prime Minister can authorise the launch of nuclear weapons, which ensures that political control is maintained at all times

  • the instruction to fire would be transmitted to the submarine using only UK codes and UK equipment; all the command and control procedures are fully independent

  • Vanguard and Dreadnought submarines can operate readily without the Global Positioning by Satellite (GPS) system and the Trident D5 missile does not use GPS at all

  • our procurement relationship with the US regarding the Trident Missile does not compromise the operational independence of our nuclear deterrent

A minimum and credible deterrent

  • we are committed to maintaining the minimum amount of destructive power needed to deter any aggressor. This requires us to ensure that our deterrent is not vulnerable to pre-emptive action by potential adversaries

  • we require a fleet of 4 submarines to maintain 1 continuously on patrol and retaining this posture is essential to assure the invulnerability of the deterrent

  • our preference is for an invulnerable and undetectable system, which allows us to maintain it at a minimum level of scale and readiness, but we believe that it should also be capable of being held at high readiness for extended periods of time

  • invulnerability and security of capability are key components of the credibility of our deterrent and contribute to overall stability

Cost

  • the Trident Alternatives Review in 2013 demonstrated that no alternative system is as capable as the current Trident based deterrent, or as cost effective

  • as set in the 2015 SDSR we estimate that 4 new Dreadnought submarines will cost £31 billion to build, test and commission, spread over 35 years, with a contingency of £10 billion. On average, that amounts to 0.2% per year of government spending

  • we expect that, once the new fleet of deterrent submarines come into service, the in-service costs of the UK’s nuclear deterrent will be similar to those of today, at around 6% of the defence budget

  • UK and US nuclear defence cooperation is underpinned by the recently renewed 1958 Mutual Defence Agreement and the 1963 Polaris Sales Agreement; among other things, these allow the UK to reduce costs by procuring Trident missiles and other components from the US while maintaining full operational independence

  • any programme to develop and manufacture a new cruise missile would cost far more than retaining the Trident D5 missile; in terms of both cost and capability, retaining the Trident D5 missile is by far the best approach

Threat

  • it is a key responsibility of government to be sure that the UK is properly protected should the future turn out to be less secure than we hope

  • in spite of the successes of arms control activities in slowing the proliferation of nuclear weapons, the number of states with nuclear capabilities has continued to grow

  • there are risks that, over the next 20 to 50 years, a major direct nuclear threat to the UK or our NATO Allies might re-emerge; a state’s intent in relation to the use or threat of use of existing capabilities could change relatively quickly: for example, there was little prior warning of the collapse of the Soviet Union

  • when the case for the UK’s independent nuclear deterrent was last presented to Parliament, by the Labour government in 2006-07, it was acknowledged that the old certainties of the Cold War were gone. It was recognised that the UK faced a growing number of diverse and complex threats in an unpredictable world

  • similar key judgements were made in the recent National Security Strategy and Strategic Defence Review. There is a risk that states with nuclear weapons, or those seeking to acquire them, might use their nuclear capabilities to threaten the UK, and attempt to constrain our decision making in a crisis or sponsor nuclear terrorism

  • therefore the government is committed to maintaining the UK’s independent nuclear deterrent to deter the most extreme threats to our national security and way of life, now and in the future

  • we know that international terrorists are trying to acquire radiological weapons. There are risks that they may try to aquire nuclear weapons; while our nuclear deterrent is not designed to deter non-state actors, it should influence the decision making of any state that might consider transferring nuclear weapons or nuclear technology to terrorists

Myths and discussion points

Myth 1. The nuclear deterrent is obsolete as it does not deter terrorism.

The nuclear deterrent wasn’t intended to deter terrorists. The UK has policies and capabilities to deal with the wide range of threats we currently face or might face in the future. Our nuclear deterrent is there to deter the most extreme threats to our national security and way of life, which cannot be done by other means.

Myth 2. The money spent maintaining a nuclear deterrent would otherwise be invested in our conventional capabilities.

Nuclear weapons remain a necessary element of the capability we need to deter threats from others possessing nuclear weapons. Conventional forces cannot deliver the same deterrent effect. The investment required to maintain our deterrent will not come at the expense of the conventional capabilities our armed forces need.

Myth 3. Submarines could become vulnerable to new technological developments such as underwater drones or cyber attack.

We believe it is unlikely there will be any radical technological breakthrough which might diminish the current advantages of the submarine over potential anti-submarine systems. In any event, we judge that a submarine will remain by far the least vulnerable of all the platform options.

Myth 4. Replacing Trident is illegal.

Maintaining a minimum nuclear deterrent is fully consistent with all our international legal obligations, including those under the NPT.

Discussion point 1. The UK does not require a nuclear deterrent as we are already protected by the US nuclear deterrent.

A potential adversary might miscalculate the degree of US commitment to the defence and security of Europe. An independent deterrent provides the assurance that it can be used to deter attacks on our vital interests. An independent centre of nuclear decision making in the UK also reinforces the overall deterrent effect of allied nuclear forces and thus enhances our security and that of NATO allies.

Discussion point 2. All the UK needs is a dormant nuclear weapons capability, from which we could re-establish a deterrent if and when specific threats emerge.

Any UK decision to give up an active credible nuclear deterrent system would, for political and cost reasons, be extremely difficult to reverse. In practice, the timeframe for re-establishing a credible minimum deterrent would probably be longer than the likely warning of any change in intent of an established nuclear power or any covert programme elsewhere to develop nuclear weapons. Also, any move from a dormant programme towards an active one could be seen as escalatory, and thus potentially destabilising, in a crisis.

Discussion point 3. We don’t need a continuous deterrent.

If we ceased continuous deterrent patrols, we could be deterred or prevented from deploying an SSBN in a crisis. The submarine is by far the least vulnerable of the platform options.

Discussion point 4. We could make do with an aircraft delivered system.

Short and medium range aircraft operating from the UK or overseas, or short or medium range land based missiles, do not provide an assured deterrent on the grounds that these options lack sufficient range. Even aircraft launched from aircraft carriers would not meet our range criteria. Furthermore, these options would be vulnerable to pre-emptive attacks, or to interception by air defence systems whilst in the air.

See our downloadable factsheet