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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; making the command and control procedures fully independent
Vanguard submarines 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
our continuous patrol is essential to assure the invulnerability of the deterrent
invulnerability and security of capability are key components of the credibility of our deterrent and contribute to overall stability
it is a key responsibility of the 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 but 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 2015 Strategic Defence and Security 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 acquire 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
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 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 which has reduced its deterrent capability to a single nuclear weapon system; we have dismantled our 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 on 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
- we remain committed to reducing the overall nuclear weapon stockpile to no more than 180 warheads by the mid-2020s.
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 international role on nuclear disarmament verification and has driven forward the first multilateral initiative involving both NWS and NNWS. This is an essential step for nuclear disarmament under strict and effective international control.
Infographic: UK’s leading role in multilateral nuclear disarmament
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.
the Trident Alternatives Review in 2013 demonstrated that no alternative system is as capable as the current Trident based deterrent, or as cost effective
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 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 missile; in terms of both cost and capability, retaining the Trident missile system is by far the best approach
Myths and discussion points
Myth 1. The nuclear deterrent is obsolete as it does not deter terrorism.
The nuclear deterrent is not 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 the most extreme threats. Conventional forces cannot deliver the same deterrent effect.
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 Nuclear non-Proliferation Treaty.
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 a nuclear submarine in a crisis. This 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