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The last time the UK government carried out a strategic defence review was in 1998. It took Labour longer than a year to complete.

Now, more than a decade later, this government is trying to complete a more ambitious process in record time - within six months.

Behind closed doors work on the strategic defence and security review (SDSR) is already well under way.

The three armed services have had to put forward a range of options for cuts.

Ministry of Defence officials privately concede that these options are "brutal".

They include scrapping one or both of the Royal Navy's new aircraft carriers currently under construction in Rosyth, Fife; grounding the RAF's entire fleet of more than 70 Tornado jets years earlier than planned; and the Army losing up to 20,000 troops.

There is still hope within the armed forces, and the MoD, that the prime minister will blink and hesitate when he has to decide where the axe should fall. But given the MoD's dire finances, that may be wishful thinking.

True, the MoD has been spared the level of cuts that most other departments are facing. But it still has to make savings of between 10 and 20%. And that is on top of a huge financial black hole in the ministry's annual budget of £37bn.

Whichever way you slice it, the cuts will be painful.

The three armed services have been under strict orders not to engage in leaks and lobbying that could undermine the process.

The government had hoped to conduct this review largely in private. But any hopes of doing this all by stealth have been dashed by MPs.

The cross-party Commons Defence Select Committee has rushed out a report that criticises the lack of consultation, the budgetary straitjacket and the "startling" speed with which the review is being conducted.

The committee warns that current military operations - namely Afghanistan - could be put at risk by the levels of cuts now being contemplated.

Even though Afghanistan is meant to be funded separately by the Treasury, the overall costs of the military commitment still swallows as much as 30% of the MoD's budget.

Rotating around 10,000 personnel in Helmand every six months does not come cheap.

No doubt the defence committee has made life more difficult for the government.

But not everyone in the MoD will be disappointed to see these arguments aired in public. It could strengthen the hand of Defence Secretary Liam Fox, who says he wants to avoid salami-slicing the military.

Instead he talks of his ambition of creating a modern armed forces prepared to face the threats of the next decade.

Dr Fox has already had a public spat with George Osborne over who should pay for replacing the Trident nuclear missile system, with the chancellor insisting that the MoD must fund the £20bn it will cost.

But the MPs on the Defence Select Committee appear to be siding with the defence secretary when they say they expect the SDSR to be "fully funded".

Liam Fox needs all the help he can get - ultimately he will not be making the decisions. It's the job of the National Security Council (NSC) - chaired by the prime minister - to decide the future shape and size of the armed forces.

The NSC is due to start its deliberations as early as next week. Again, behind closed doors.

At the heart of the debate is the apparent contradiction of the government's objectives. On the one hand there's the urgency to save money. But at the same time the wish to preserve and enhance Britain's place in the world.

Foreign Secretary William Hague insists there will be no "strategic shrinkage". But can you do both?

These are very difficult decisions for David Cameron.

But few in high office would be prepared to admit that Britain can no longer afford to be a major military power.