Comment: Trident review is bad news for the idealists

The coalition's Trident nuclear deterrent review is a setback for the idealists and a disaster for the Liberal Democrats.

Today was supposed to be a festival of differentiation for the Lib Dems. The Trident review was set up to paper over the coalition's gaping divide on the issue of Britain's future as a nuclear power. Thanks to the coalition's innovative solution of putting off the final decision on Trident's like-for-like renewal until after the next general election, the stage was set for a review which would look at "the case for alternatives".

The Ministry of Defence had as little to do with this Lib Dem project as possible. It was always something the military opposed. And with the departure of Nick Harvey the absence of Lib Dems from the department reduced their relevance still further. Still, the hope was that those alternatives might prove compelling. Setting them out clearly would trigger a debate which might win the Lib Dems one or two more votes come 2015.

Unfortunately for those who struggle to see why Britain needs to spend so much money on a nuclear deterrent, the watered-down versions which the Lib Dems are now interested in risk being neither here nor there. The central problem is that most of the solutions involving a reduction in Britain's nuclear capability require paying for two more new boats for a 'bridging period'. This means dropping down to a three-boat solution (we need four to operate a continuous deterrent) would actually end up costing the taxpayer more.

The Lib Dems blame Labour. They say these extra costs would not have been necessary in 2006, at the time of the last government's white paper. Seven years later and the party is now having to confront the fact those massive savings are no longer realistic. The lure of huge savings has disappeared at a stroke.

This obliges Alexander, stuck with the Trident nuclear defence system for the time being, to assess the options for "stepping down the ladder" instead. Now the Cold War environment is over, he argues, the guarantee of nuclear destruction "does not need to rest on a hair trigger".

The review itself sounds optimistic. "The analysis has shown that there are alternatives to Trident that would enable the UK to be capable of inflicting significant damage such that most potential adversaries around the world would be deterred," it states. Hawks up and down the country will be delighted to learn that even if the Lib Dems do get their way the UK would be able to send most potential enemies to oblivion.

But 'most' is not 'all'.

When it comes down to it, Wellington once said, the real secret of warfare is "guessing what is on the other side of the hill". Herein lies the weakness of the Liberal Democrats' argument: it represents a step into the unknown. Over a 30-year period, the global context for Britain's nuclear deterrent can shift dramatically. Change can be unexpected and rapid; the 2010 strategic defence and security review, for example, rated the perils of an Arab uprising a tier-three threat, lower than the nuclear attack danger placed in tier two.

The Lib Dem position will be cleared up at its autumn conference this September. The party's leadership does not believe in nuclear disarmament, unlike a sizeable chunk of its grassroots membership. Alexander indicated it is likely to plump for the smallest step down the nuclear deterrence ladder available: a drop down to the doctrine of 'focused deterrence' in which a nuclear deterrent can be maintained for a specific period and for a specific threat.

It sounds appealing. The problem may be it is unrealistic. "Deterrence is deterrence," former first sea lord Michael Boyce told Alexander earlier. You either do it properly, he suggests, or you don't. "You will not have a deterrent if you do not have a continuous at-sea deterrent – in which case, why do it at all? This is a step towards nuclear disarmament."

The Liberal Democrat position will not satisfy the idealists or, for that matter, the pragmatists. Just put yourself in the scenario that Britain, having mothballed its nuclear submarines pending the emergence of a new existential threat, suddenly realises it needs an active deterrent again. Alexander revealed it would "of course" take "several years" for a credible threat to be viable once more. The decision to reactivate could be unhelpful in diplomatic terms. The delay in re-establishing a deterrent could prove fatal.

As today's review by Cabinet Office officials states, the judgement as to whether stepping back from a continuous deterrent is acceptable to Britain is a political one. Nuclear weapons are a curse on humanity but pose a threat which has to be lived with. How you do that becomes a risk assessment exercise bound up as much in ideas of nationalistic jingoism and Britain's continuing global influence as it is in cold-hearted military calculation.

The Liberal Democrats hope that by drawing attention to the issue their very different view from that of the Conservatives and Labour will gain traction with some voters. Their problem is this exercise has made it harder for voters to agree with them.

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