By Dr Robert Crowcroft

The leak of a confidential letter written from Liam Fox to David Cameron has now been widely picked up in the press. The upshot is Fox's complaint that the Strategic Defence Review process is fast losing credibility and coherence because of the Treasury's willingness to subordinate national security to a timetable chosen by Cameron and George Osborne for very political reasons to try get the bad news out of the way, in one go, in the Comprehensive Spending Review. While one has to admire the political gusto of Cameron and in the unlikely event he pulls it off, it would constitute a masterstroke nonetheless Fox is right: that these kind of grave decisions cannot be taken in such a short space of time (while Guardianistas will vomit righteous indignation, the fact is that Defence is different from other departments, i.e. more important), and that there has been an inadequate scope for debating the future of Britain's role in international politics.

The basic problem is this: the UK is currently engaged in a war in Afghanistan, and will be there for about five more years. This requires proper funding of the ground forces which wage counterinsurgency conflicts. However, to fund the Afghanistan commitment, the Army will need to be shielded while the other services are squeezed the aircraft carriers potentially face the axe, as do other classes of surface vessel, several kinds of aircraft, and even the Trident submarines. The strategic dilemma facing the country is whether future security crises requires long-term occupation and nation-building on the Afghanistan model, or whether the threat, and demands on the UK, will look quite different. If the future is not more Afghanistans, then favouring the ground forces now by badly weakening the naval and air power available to the country risks calamitous damage.

I have no idea what the current state of the debate is within the MOD, let alone the National Security Council. The most probable eventual outcome of the Defence Review process will be incoherence and a lack of clear choice. But, from what we can tell, Cameron has worked to protect the Army in other words, focus resources on the short-term challenge of Afghanistan, whether from considered strategic judgement or fear of deleterious political consequences of letting down 'our boys', we cannot know while Fox has taken a more long-term view and sought to preserve Britain's maritime power. Fox's letter is a clear bid to outflank the Treasury and bounce the Coalition into slowing down the debate and protecting the MOD from unsustainable cuts to its budget. If it works, then all well and good; Fox will have won a major trial of strength and emerge politically stronger. But the letter also serves the dual purpose of offering Fox a potential exit strategy from office; he could return to the backbenchers, head held high and popular with most of the Conservative party for standing up to a government they see as run by people who are a worrying shade of pink and with a disconcerting habit of wearing open-toed sandals. From there, Fox could rebuild his reputation as a heavyweight (a reputation which has diminished in recent months) and then simply wait and see what happens in the future. William Hague's time as the standard-bearer of the Conservative Right is probably over, and David Davis is never going to have the requisite standing. But Liam Fox might, and if he plays his cards correctly in the intervening period could eventually name his price for inclusion in a future, post-Cameron Conservative leadership.

The Prime Minister will be desperate to avoid a resignation on a totemic issue like Defence, and so will probably seek a formula to keep Fox within the government while further damaging his stature (from afar, of course). Whether Fox will submit to being spiked in this way is the question. But, either way, the Defence Review is now a pawn in a fairly conventional kind of political game.

Robert Crowcroft is a specialist on British politics and defence.