S T R A T E G I C    D E F E N C E    R E V I E W




60. Deterrence is about preventing war rather than fighting it. All our forces have an important deterrent role but nuclear deterrence raises particularly difficult issues because of the nature of nuclear war. The Government wishes to see a safer world in which there is no place for nuclear weapons. Progress on arms control is therefore an important objective of foreign and defence policy. Nevertheless, while large nuclear arsenals and risks of proliferation remain, our minimum deterrent remains a necessary element of our security.

61. The Strategic Defence Review has conducted a rigorous re-examination of our deterrence requirements. This does not depend on the size of other nation's arsenals but on the minimum necessary to deter any threat to our vital interests. We have concluded that we can safely make further significant reductions from Cold War levels, both in the number of weapons and in our day-to-day operating posture. Transparency about nuclear weapons holdings also plays a part in arms control and, although we cannot give precise details of all aspects of our deterrent, we intend to be significantly more open in some areas.


62. With the withdrawal of the last RAF WE177 bombs in March 1998, Trident is our only nuclear weapon. We need to ensure that it can remain an effective deterrent for up to 30 years. This is why we need a force of four Trident submarines. The last of these, VENGEANCE, will be launched later this year.

Trident submarine, HMS VICTORIOUS, on trials.

63. Similarly, we must judge our weapons requirements against the worst circumstances that we might face over Trident's life, however remote they may seem today. The credibility of deterrence also depends on retaining an option for a limited strike that would not automatically lead to a full scale nuclear exchange. Unlike Polaris and Chevaline, Trident must also be capable of performing this 'sub-strategic' role.

64. Against this background, taking into account Trident's greater accuracy than Polaris, the Review has concluded that we need a stockpile of less than 200 operationally available warheads. This is a reduction of a third from the maximum of 300 announced by the previous government and represents a reduction of more than 70% in the potential explosive power of the deterrent since the end of the Cold War.

Explosive Power of United Kingdom
Operationally Available Warheads


The chart compares the explosive power of our operationally available weapons during the 1970s and 1980s with the previous government's plans for UK nuclear forces by the end of 1999 and SDR decisions. The charts do not include United States systems formerly operated by the United Kingdom under dual key arrangements.

65. We have also concluded, in the light of improved strategic circumstances, that the 58 missile bodies we have already purchased are sufficient to maintain a credible deterrent.

Operating posture

66. We intend to maintain continuous at-sea deterrent patrols, not least to avoid misunderstanding or escalation if a Trident submarine were to sail during a period of crisis. But the relaxation of tension and vast improvement in current strategic conditions since the end of the Cold War also permit us to adopt a reduced day-to-day alert state.

67. We will have only one submarine on patrol at a time, carrying a reduced load of 48 warheads. This compares with the previous government's announced ceiling of 96. This is a huge step change from the Polaris era. Although Trident is now our only nuclear weapon and covers both strategic and sub-strategic requirements, the potential explosive power deployed on a Trident submarine is one third less than a Polaris submarine armed with Chevaline.

68. The submarine's missiles will not be targeted and it will normally be at several days 'notice to fire'. This reduced state of alert will enable greater use of ballistic missile submarines for secondary tasks such as exercises with other vessels, equipment trials and hydrographic work. Similarly, current threat levels do not require large numbers of conventional forces permanently allocated to the protection of the deterrent. We will, however, ensure that we can restore a higher state of alert should this become necessary at any time.

Arms Control

69. Arms control plays an important part in our security. The United Kingdom is party to several arms control agreements which have contributed significantly to lowering tensions in Europe and to limiting the spread of weapons of mass destruction. We are committed to building on these agreements to further develop international confidence and stability. A key current task is the revision of the 1990 Conventional Armed Forces in Europe Treaty to ensure its continued relevance in the new strategic circumstances. We are also contributing to a number of other arms control initiatives and enhancing our national monitoring capabilities (see paragraph 49).

70. On nuclear arms control, the Government hopes for further bilateral reductions in US and Russian strategic weapons through the Strategic Arms Reduction Treaty process. We also hope to see progress towards reducing the thousands of Russian shorter range weapons. Our own arsenal, following the further reductions described above, is the minimum necessary to provide for our security for the foreseeable future and very much smaller than those of the major nuclear powers. Considerable further reductions in the latter would be needed before further British reductions could become feasible.

71. The Nuclear Non-Proliferation Treaty and the Comprehensive Nuclear Test Ban Treaty are key elements in nuclear arms control. We have ratified the Comprehensive Nuclear Test Ban Treaty and we hope that other states - particularly including India and Pakistan - will quickly follow our example to enable it to enter into force. Greater transparency about nuclear programmes also adds to international trust and security. The measures described earlier in this chapter will be a significant step in this direction.

72. We can also be more open about fissile materials. Our current defence stocks are 7.6 tonnes of plutonium, 21.9 tonnes of highly enriched uranium and 15,000 tonnes of other forms of uranium. The reduction in planned warhead numbers will allow us to place a surplus of 0.3 tonnes of weapons grade plutonium under international safeguards (along with surplus non-weapons grade material). We will also cease exercising our right as a nuclear weapon state under the Nuclear Non-Proliferation Treaty to withdraw fissile material from safeguarded stocks for nuclear weapons. Future withdrawals will be limited to small quantities of materials not suitable for weapons purposes and the details will be made public. No material withdrawn from safeguards will be used in nuclear weapons. All planned future reprocessing will also be carried out under safeguards and we intend to publish an initial report by 2000 on past defence fissile material production.

UN Special Commission (UNSCOM) weapons inspectors in Iraq.

(By courtesy of UNSCOM)

73. The effectiveness of arms control agreements depends heavily on verification. The United Kingdom has developed particular expertise in the monitoring of fissile materials and nuclear tests. We plan to add to this by developing capabilities which could be used to verify reductions in nuclear weapons, drawing on the expertise of the Atomic Weapons Establishment at Aldermaston. This will begin with a study lasting some 18 months to identify the technologies, skills and techniques required and what is available in this country.


74. We estimate the total cost of acquiring the Trident system to be about 12.5Bn, almost all of which has already been spent. On the basis of our experience so far, we estimate that the running cost of the Trident submarine force will average some 280M a year over its life time. The current annual cost of our warhead and fissile material programme is some 400M a year. About one third is directly related to Trident, almost a third is related to costs arising from previous nuclear weapons and the remainder is infrastructure costs.

75. These are very substantial costs but need to be seen in perspective. The annual cost (including the continuing costs from earlier programmes) is little more than 3% of the defence budget. This is not a disproportionate investment in a capability of such vital importance to our national security.