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Disarmament Diplomacy

Issue No. 56, April 2001

Conventionally-Armed UK Trident?

By Robert Green


Growing US doubts about the effectiveness of nuclear deterrence against what it identifies as the current primary threat - extremists armed with weapons of mass destruction (WMD) - have prompted a major reassessment of America's nuclear posture. Several nuclear weapon experts now argue that deterrence through threatened use of precisely targetted conventional munitions would be preferable and more credible in most cases. Meanwhile, US Navy research has established the feasibility of converting at least four of its nuclear-armed Ohio class submarines to carry a formidable mix of conventional armament capable of proportionate, effective responses while remaining invulnerable, which is clearly what the US feels it requires to protect what it sees as its vital interests worldwide.

In the context of this reconsideration of posture and deterrent capacity, there are a number of reasons why the US should be concerned about the new sub-strategic role of the UK Trident nuclear-armed submarine system: the risk of confusion with US Trident; lack of credibility; and, most seriously, the possibility of use which the US did not endorse. Meanwhile, the UK government faces growing domestic legal challenges to Trident deployment. A decision has to be taken whether or not to replace the system around 2007. Following recent indications that the Royal Navy "wants to lead in nuclear disarmament", a confluence of pressures could persuade it to recommend that UK Trident be converted to a conventionally-armed submarine force. In so doing, the UK could become the first of the P-5 nuclear-weapon states to renounce nuclear deterrence, thereby gaining the opportunity to wield unprecedented influence in leading the drive for a Nuclear Weapons Convention and a nuclear-weapon-free world. At the same time, however, the Royal Navy would strengthen its role as joint maritime enforcer with the US in protection of Western vital interests, which would raise new concerns for the peace movement. This paper outlines the main arguments for and against such a bold move.

Doubts about Nuclear Deterrence

In mid-April 2001, British newspapers picked up on a Washington Post article headlined: "US Studies Developing New Nuclear Bomb".1 In it, Walter Pincus reported that the Pentagon is due to report to the Senate in July 2001 in response to a Republican request in the Defense Authorization Bill to find a way of destroying "hardened and deeply buried targets". The desire for such a capability is driven by the realisation, as a senior adviser to US Defense Secretary Donald Rumsfeld told the Washington Post, that, for example, President Saddam Hussein would not be deterred by any of the nuclear warheads in the US arsenal, "because he knows a US president would not drop a 100-kiloton bomb on Baghdad" in order to counter Iraq's WMD.

Following the Gulf War, several leading US experts on nuclear weapons reassessed the effectiveness of nuclear deterrence, especially against threats by so-called "rogue" states with WMD-armed ballistic missiles. Israel had become the first state in possession of nuclear weapons to be directly attacked with ballistic missiles, experiencing 39 Scud attacks, some of them against its second largest city Tel Aviv. For several weeks Israelis wearing gas masks had sheltered in basements, because it was known that a chemical warhead had been developed for Iraq's Scud missile. Saddam Hussein had demonstrated that he had not been deterred by Israel's nuclear arsenal. Subsequently, the Western nuclear-armed coalition was further shocked to find that instead he had been provoked by Israel's clandestine acquisition of nuclear weapons - condoned by the coalition - to follow suit, despite Iraq being a signatory to the Non-Proliferation Treaty (NPT).

In a 1991 article in Strategic Affairs entitled "Countering the Threat of the Well-Armed Tyrant", Los Alamos National Laboratory nuclear weapon analysts Thomas Dowler and Joseph Howard II argued that the US had no proportionate response to a rogue dictator who uses chemical or biological weapons against US troops.2 The consequent risk of "self-deterrence" underlies a recent influential paper by Stephen Younger, head of nuclear weapons research at Los Alamos, called "Nuclear Weapons in the 21st Century".3 In it, he challenged decades of military thinking by suggesting that precision-guided conventional munitions could replace nuclear warheads on most US strategic missiles. Because of improvements in accuracy, "advanced conventional weapons delivered by ballistic or cruise missiles could defeat many [military sites] that are presently targeted by nuclear weapons", such as mobile missiles and manufacturing sites for chemical and biological weapons. However, no doubt concerned that he might be arguing away his job, he recommended that the US should consider developing a new generation of "small" nuclear weapons to handle the few military tasks for which he claimed nuclear weapons are indispensable.

In his speech at the National Defense University on May 1, 2001, President George W. Bush showed that he was sympathetic to these ideas, when he called for deep, possibly unilateral cuts in the US nuclear stockpile, along with development of a still unproven ballistic missile defence system. In some ways, this was a revived response to what Ronald Reagan had seen as the unacceptable and immoral prospect of relying forever on Mutual Assured Destruction (MAD) for US security. What has changed since the "Star Wars" era is that Bush has accepted the experts' potentially heretical thesis. He is the first US President publicly to doubt that nuclear deterrence would work against what he now sees as the greatest threat to Americans: extremists armed with WMD warheads intent on blackmailing the US. Moreover, both his Vice-President, Dick Cheney, and Secretary of State, General Colin Powell, are known to have rejected use of nuclear weapons against Iraqi forces in the Gulf War.4 In the demonology of nuclear deterrence, such perceived lack of faith in the utility of your own weapons means that any future US nuclear threat in a similar scenario will lack credibility.

"Small" Nukes No Answer

An important new report by the Federation of American Scientists (FAS)5 argues that the Pentagon's initial answer to the requirement to destroy buried and hardened targets - the B61-11 nuclear weapon with a variable yield of 0.3-300 kilotons - penetrated only 20 feet into dry earth in tests, even when dropped from 40,000 feet. A nuclear blast at that depth, the report says, "will simply blow out a huge crater of radioactive material, creating a lethal gamma-radiation field over a large area".

The author, physicist Robert Nelson from Princeton University, reports that data from experiments at the US Nevada test site demonstrates that, to contain even a 0.1 kiloton explosion, the weapon needs to be buried at a depth of at least 230 feet, and 650 feet for a 5 kiloton device. However, even with rocket assistance, penetration to such depths is impossible because the weapon casing could not be made strong enough to withstand the huge impact and temperatures: the theoretical depth limit is about 100 feet. In addition, very low yield nuclear weapons are more sensitive to shock, risking a greater explosive power than expected (about 10 kilotons is the natural energy scale for a fission nuclear weapon, which it would tend to revert to if damaged).

Robert Sherman, head of the FAS nuclear security project, adds: "We have gone 56 years without a nuclear weapon being used anywhere. There is universal recognition that once you use the first nuclear weapon it becomes a great deal easier for someone to use the second. It's incredibly stupid to think you can use a small nuclear weapon, cross the nuclear firebreak and get away with it. Trying to sell it on the rationale that it can be used without collateral damage and that will be the end of it... is incredibly irresponsible." In addition, the 1996 World Court Advisory Opinion implicitly confirmed that the use of a nuclear weapon in such circumstances would inevitably break international humanitarian law, and risk escalation to nuclear war. General Lee Butler, Commander-in-Chief of US Strategic Command from 1992-94, had this to say in 1998: "In a single act, we would martyr our enemies, alienate our friends, give comfort to the non-declared nuclear states and impetus to states who seek such weapons covertly."6

The FAS report argues that the precision guidance, penetration capability, and explosive power of conventional weapons have improved dramatically since the Gulf War. It cites several existing US weapons capable of destroying hardened targets buried up to 50 feet below ground. For example, the US GBU-37 guided bomb is already thought to be capable of disabling a silo-based intercontinental ballistic missile - a target formerly thought vulnerable only to nuclear attack.

Conventionally-Armed Trident?

The START II Treaty, signed in 1993, limits US and Russian nuclear-armed ballistic missile-firing submarine (SSBN) forces to 14 hulls each. In October 1993, the Ohio class submarine Nebraska fired a Trident II D5 missile to test the use of the Global Positioning System (GPS) satellite navigation system for fixing the location of the re-entry vehicles. This was part of a series of trials which established the feasibility of combining precision terminal guidance with a kinetic energy warhead at ranges of up to 6,000 nautical miles.7 Replacing the nuclear warheads with a simple tungsten plug can cause sufficient shock and cratering to neutralise most hardened counter-proliferation targets and weapons of mass destruction, because of the enormous kinetic energy at full re-entry velocity in excess of 7 kilometres a second - and with any contamination coming only from the WMD being targeted, which should encourage the possessor to store them well away from populated locations.

In November 1999, Jane's Defence Weekly reported an interview with US Secretary of the Navy Richard Danzig on plans to convert the first four of the 18 Ohio class SSBNs, scheduled to be decommissioned under START II, to a conventionally-armed missile role.8 With a hull life of 42 years, even the Ohio - launched in 1979 - could remain in service until 2021. Most of its 24 launch tubes would be altered to accept canisters carrying seven Tomahawk cruise missiles each, plus an option for some conventionally-armed Trident missiles, or a shorter range ballistic missile under development called the Navy Tactical Missile System. With a full cruise missile conversion, each submarine would be able to launch up to 154 missiles fitted with a variety of conventional warheads, compared with 24 such missiles in nuclear-powered attack submarines. The two remaining tubes would be configured to allow up to 66 Special Forces commandos to access two midget submarines - to be known as the "Advanced SEAL Delivery System" - to carry out covert shallow water and amphibious operations. These would be attached to the deck of the Trident submarine over the two launch tubes.

In NATO's conflict with Serbia in 1999, 25% of the cruise missiles fired came from US and UK submarines. Danzig commented that just one of these converted SSBNs "could carry almost as many Tomahawks as were fired by the USN in the Kosovo crisis. Considering the 2,000 km range expected from the Tactical Tomahawk, due to enter service in 2004, this is a capability that should be exploited... We would then free up surface ships to do things like ballistic missile defence and self-defence." He added that converting each SSBN would cost about $550 million. At present, there is resistance to such conversion from the surface US Navy, because such relatively invulnerable, inherently stealthy and autonomous "underwater battleships" (with no need to refuel, and using existing hulls) would be a serious competitor for their planned multi-billion dollar surface fleet upgrade, involving 32 new DD-21 destroyers costing $800 million each.

US Concerns About UK Trident

Ever since the US allowed the UK to acquire Polaris, Trident's predecessor system, in 1962, it has had understandable concerns about the implications and complications for its own nuclear strategy. Kennedy's Defense Secretary, Robert McNamara, condemned small nuclear forces as "dangerous, expensive, prone to obsolescence and lacking in credibility as a deterrent."9 The contradictions and limitations of trying to encapsulate a credible capability in one system have become more apparent with Trident now the sole delivery system for the UK nuclear arsenal. For example, the UK government felt the need to claim an added sub-strategic capability by announcing that it has a "degree of flexibility in the choice of yield for the warheads on its Trident missiles."10

Bearing in mind that sub-strategic nuclear weapons would be the first and most likely ones to be used, there is a risk that use of a UK Trident missile would be misidentified as a US Trident launch. Commander Michael Codner, of the Royal United Services Institute, warns: "Trident in the sub-strategic role is far less flexible as an instrument of coercion than a tailor-made system in that it is difficult to distinguish the sub-strategic from the strategic threat in the perceptions of the potential aggressor. The range of the system is the same in both cases; there is no identification of the platform with a particular piece of territory and therefore no evidence of commitment; and there is presumably no indication to surveillance systems on launch that an attack is sub-strategic. For that one must count the number of detonations."11

Another US concern relates to the possibility that the UK would use Trident when it is not in the US national interest. In the Falklands War, rumours abounded that a UK Polaris SSBN was moved out of range of Moscow and within range of Buenos Aires. If Argentine aircraft had sunk one of the troopships before the landing force had got ashore, the British might have been forced to withdraw or risk defeat. What would Mrs. Thatcher have done? Polaris had clearly not deterred Argentina's President Galtieri from invading. With victory in his grasp, it is doubtful that he would have believed even Thatcher would have seriously threatened a nuclear strike on Argentina. If she had, Galtieri would have very publicly called her bluff and relished watching President Reagan trying to rein her in.12

Implications for UK Trident

All this has serious implications for the UK's four new SSBNs. Some former Royal Navy colleagues have indicated to the author that they would support getting rid of the nuclear weapons "provided that a conventional role is found for the submarines". In the 2000-2001 edition of Jane's Fighting Ships, Editor Captain Richard Sharpe RN (Ret'd) - a former nuclear submariner - reported the 1993 US Navy test-firing of a GPS-guided Trident missile "...as a step towards the aim of a conventional kinetic energy weapon". He added: "The UK government has said it has no plans to deploy conventional warheads in Trident."13

With the increasing cost of high-technology warships, the Royal Navy is steadily shrinking. As it learned the hard way in the Falklands War, the vulnerability of surface ships to missile attack is extremely expensive and difficult to counter, and ever-quieter submarines can now deliver them from stand-off range. If it wants to stay in the same league as the US Navy, it cannot afford to ignore the option of converting UK Trident to conventional armament - especially as, like the Trident system itself, the research, development and production of the modular systems would be done by the US.

UK Trident and Nuremberg

The current UK government is widely acknowledged as the most constructive among the nuclear-weapon states. In the 1998 Strategic Defence Review, it unilaterally cut its nuclear arsenal by a third - at 200 warheads, it is now the smallest of the P-5 - and announced that it had relaxed Trident's notice to fire from "minutes" to "days". Last year it was credited with a key role in achieving the 2000 NPT Review Final Document incorporating a plan of action on disarmament measures, and subsequently helping to build support for the New Agenda group's UN resolution consolidating this achievement, not least with the US.

However, the government is under serious pressure from the Trident Ploughshares non-violent direct action campaign, which is exposing what it persuasively argues to be the illegality of the current deployment of the single UK SSBN on so-called "deterrent" patrol. Citing the 1996 World Court Advisory Opinion, Trident Ploughshares has achieved sensational acquittals in jury trials of activists in both Scotland and England, This campaign is gaining support among legislators and church leaders, particularly in Scotland, where the Faslane naval base on the River Clyde is home to the Trident force. As with the campaigns to ban slavery, and now landmines, and to establish an International Criminal Court, the anti-Trident campaign is succeeding because of a deep and growing awareness that it is on the right side of morality, commonsense, the law and public opinion - and that the US is not and can not be relied on for leadership, or even responsible behaviour.

The basic argument of Trident Ploughshares is simple and powerful: nuclear weapons eight times as destructive as the one which devastated Hiroshima could never be used lawfully, so their threatened use must also be illegal. The Nuremberg Principles are being brought to bear on the Royal Navy, which obviously does not want to be accused of threatening crimes against humanity and peace. Vice Admiral Sir Jeremy Blackham, Deputy Chief of the Defence Staff (Equipment Capability) recently observed: "I suspect we are all going to find international law, as it applies to conflict, a harsh taskmaster."14

The Royal Navy's leaders must be increasingly disturbed and frustrated by this prospect, and by the reality that the weapon system of four of its most prestigious and costly capital ships is currently impotent in responding to what it sees as the most serious and intractable threats. In 1980, when Mrs Thatcher overruled the Chiefs of Staff Committee and insisted on replacing Polaris with Trident, the First Sea Lord at the time described the new system as "a cuckoo in the Naval nest". In light of the above problems, perhaps it is no surprise that an anonymous senior spokesperson in the Ministry of Defence is reported to have stated: "The Royal Navy wants to lead in nuclear disarmament."

A New World Role for the UK?

A decision on whether to replace UK Trident apparently has to be taken by around 2007. This will offer the opportunity to renounce nuclear weapons, and replace them with a more credible, practical and lawful conventional deterrence system, which the US Navy is developing anyway. With four conventionally-armed Trident submarines, the Royal Navy's submarine service - diverted since acquiring Polaris into the essentially political power game of nuclear deterrence - would be able to focus fully on what Vice Admiral Blackham describes as "precision engagement" to prevail in the three key military objectives: deterrence, coercion and combat.

For maximum kudos, the UK government should announce this step at the 2005 NPT Review Conference. The first "breakout" by one of the P-5 would be sensational, and would transform the nuclear disarmament debate overnight. The UK would gain a major new world role which would be enormously popular, with its Prime Minister an immediate candidate for the Nobel Peace Prize. In NATO, with Lord Robertson as Secretary General, the UK would wield unprecedented influence in leading the drive for a non-nuclear strategy - which must happen if NATO is to sustain its cohesion. It would create new openings for applying pressure, particularly to the US and France, and heavily influencing India, Israel and Pakistan, and others intent on obtaining nuclear weapons. Moreover, it would open the way for a major reassessment by Russia and China of their nuclear strategies, for all nuclear forces to be de-alerted, and for multilateral negotiations to start on a Nuclear Weapons Convention.

Out of the Nuclear Frying Pan into the Conventional Fire?

The downside of this scenario is that conventional deterrence maintains the same unstable, hostile attitude between states as nuclear deterrence, stimulating several arms races and inhibiting co-operation in promoting true security. Nevertheless, there is a fundamental difference which leads me to recommend it as an immediate stopgap replacement for nuclear deterrence. If deterrence based on conventional weapons fails, the damage would generally be confined to the belligerent states - and the environmental damage would usually be reparable. What is at stake from the failure of nuclear deterrence is the devastation and poisoning of not just the belligerents, but potentially of most forms of life on Earth.

However, what about the impact of such conversion on missile proliferation? Clearly, France, Russia and China would try to copy the US and UK conventional multi-role former SSBNs. With the US feeling the need to build ballistic missile defences, it has a strong vested interest - though it has yet to show awareness of this - in leading international initiatives to constrain and roll back the ballistic missile race. To be credible, it would therefore need to forego the use of conventionally-armed Trident missiles, which would also rule out this option for the UK. Britain, too, has to weigh its degree of commitment to efforts to prevent missile proliferation through diplomatic, arms control, and other non-military measures. As a more technical side-issue, there would be incompatibilities in having an intercontinental range missile in the same submarine as special forces needing to be inserted close to the area of conflict.

A related, major concern is that the conventional multi-role former SSBN would come into its own as the pre-eminent maritime coercion platform. As demonstrated in Sudan and NATO's intervention in Kosovo, so-called 'precision-guided' conventionally-armed cruise missiles are not always used lawfully. Pressure would mount for more nuclear-powered hunter-killer submarines to counter them, while poorer navies would opt for conventionally powered ones. As yet, there is still no solution to the problem of safely disposing of old nuclear submarine reactors using highly-enriched uranium, while the risk of an environmental catastrophe would increase if a nuclear submarine was found and sunk.

The peace movement, however, as well as advocates of converting Trident, have to confront difficult and challenging questions. Acquisition by the P-5 of their nuclear arsenals involved probably the greatest investment in financial, political and human terms since the Second World War. Short of a detonation of a modern nuclear weapon in a populated area (with the huge risk of escalation to nuclear war), none of these states is likely to be prepared to risk breaking out of the nuclear club without finding a replacement system which offers clear advantages to balance the perceived loss of security, as it would appear after fifty years of their own propaganda. The only durable solution, therefore, may be to exploit the decoupling of nuclear weapons from the P-5 which conventional multi-role former SSBNs could achieve, and then focus on replacing conventional deterrence with a paradigm which sees security as a safety net for all, not a "win/lose" military game. Military alliances are obsolete and divisive: ultimately, common security will only be achieved by practising minimal non-provocative defence, relying on enforcement of international law through the UN, and transferring resources from military procurement to training in peacekeeping and mediation skills.


A confluence of developments in the US, driven by a loss of faith in nuclear deterrence against the most serious threat of extremists armed with WMD, points to a "win-win" solution for the Royal Navy, the UK and the worldwide anti-nuclear movement (though regrettably not yet for the peace movement). Nuclear-armed UK Trident is a major impediment to the Royal Navy role because its armament is militarily useless, and its use - and therefore any threatened use - would be unlawful.

A UK decision, exploiting a current US Navy proposal, to convert its four Vanguard class Trident submarines to carry a mix of precision-guided conventional armaments would solve this problem. In so doing, the UK would gain huge kudos as the first of the P-5 to break out from reliance on nuclear weapons for its security, and would position itself to take a leading role in the struggle to secure an enforceable global treaty with a verifiable plan to eliminate nuclear weapons.

However, the prospect of conventional deterrence fanning arms races in missiles and nuclear-powered submarines poses serious new risks for international stability, peace and the environment, and the peace movement will therefore oppose conventionally-armed Trident. My proposal is not intended as a long-term answer, but as a pragmatic first step to loosen the grip of nuclear deterrence and provide the UK government with a militarily credible alternative to nuclear-armed Trident. The only truly lawful, durable solution lies in moving from military alliances to common security, practising minimal non-provocative defence.

Notes and References

1. Walter Pincus, "US Studies Developing New Nuclear Bomb", Washington Post, 15 April 2001.

2. See Robert W. Nelson, "Low-Yield Earth-Penetrating Nuclear Weapons", The Journal of the Federation of American Scientists, January/February 2001, Volume 54, Number 1, http://www.fas.org/faspir/2001/v54n1/weapons.htm.

3. Walter Pincus, "Nuclear Expert Challenges US Thinking on Warheads", Washington Post, 24 October 2000.

4. Colin Powell, A Soldier's Way (Hutchinson, London, 1995), p.324.

5. Robert W. Nelson, "Low-Yield Earth-Penetrating Nuclear Weapons", The Journal of the Federation of American Scientists, January/February 2001, Volume 54, Number 1.

6. General Lee Butler, "A Voice of Reason", The Bulletin of the Atomic Scientists, May/June 1998, p.61.

7. Jane's Fighting Ships 2000-2001, p.792.

8. Jane's Defence Weekly, 24 November 1999, p.40.

9. John Baylis, Ambiguity and Deterrence (Oxford University Press, 1995), pp.300-301.

10. 'Sub-Strategic Use of Trident', letter from C.H.J. Davies, UK Ministry of Defence, to Dr. E. Waterston, October 27, 1998.

11. Commander Michael Codner RN (Ret'd), Assistant Director (Military Sciences), Royal United Services Institute, London, The New International Security Review 1998, p. 25.

12. Robert Green, The Naked Nuclear Emperor: Debunking Nuclear Deterrence (Disarmament & Security Centre, PO Box 8390, Christchurch, New Zealand, 2000), p.12.

13. Jane's Fighting Ships 2000-2001, p.748.

14. Vice Admiral Sir Jeremy Blackham KCB , "The Apotheosis of 21st Century Warfare", RUSI Journal, December 2000, pp.64-68.

Commander Robert Green, Royal Navy (Retired) served in the British Navy from 1962-82. As a Fleet Air Arm Observer (Bombardier Navigator), he flew in Buccaneer carrier-borne nuclear strike aircraft 1968-72, then in anti-submarine helicopters equipped with nuclear depth-bombs 1972-77. On promotion to Commander, he spent 1978-80 in the Ministry of Defence as Personal Staff Officer to the Assistant Chief of Naval Staff (Policy), who was closely involved in the decision to replace the Polaris force with Trident. In his final appointment as Staff Officer (Intelligence) to Commander in Chief Fleet, he was responsible for intelligence support for Polaris as well as the rest of the Fleet. Having taken voluntary redundancy in 1981, he was released after the Falklands War. The break-up of the USSR followed by the Gulf War caused him to speak out against nuclear weapons. He became UK Chair of the World Court Project in 1991. He is now working in the Disarmament & Security Centre in Christchurch, New Zealand. His latest book, The Naked Nuclear Emperor: Debunking Nuclear Deterrence - A Primer for Safer Security Strategies, was published in 2000.

© 2001 The Acronym Institute.