Francis Tusa: No wonder Jack Tar's jolly as minister ringfences aircraft carriers and Trident replacement – for now at least

"THIS is not designed to cover areas of capability, that's for the Strategic Defence Review," Bob Ainsworth said as he announced the release of the defence green paper, the policy discussion document that is meant to set the exam questions for the SDR.

Strange, but during questions, he managed to produce some pretty hard and fast conclusions about what the SDR would produce, even before the formal review process had begun. For a start, the replacement of Trident is not up for debate and discussion, so that's ringfenced. As a result, it is simple to make further assumptions on the numbers of frigates, maritime patrol aircraft and other assets that will be needed to protect the future deterrent. And then, Mr Ainsworth was astonishingly open on the fate of the aircraft carriers. "We're already committed (to the carriers]," he said, adding: "We need to be able to deploy effective armed forces with all of the forces they need. The SDR would have to be pretty radical to say these requirements would not be needed."

He also added that substantial sums had already been spent on the ships, and steel was being cut. So this programme would also now be seen to be ringfenced. And, as with the deterrent, that means one can make reasonable assumptions on the need for more escort ships, aircraft to fly off the carriers, and so forth.

All of this adds up to some fairly clear "do not cross" lines that will guide the SDR. At the same time, these announcements would seem to demonstrate that if there is – at this stage – a "winner" from the services' internecine battles, it is the beleaguered Royal Navy. Carriers safe, along with their supporting vessels, deterrent safe, with the required supporting forces.

This would seem to be some form of "victory" for those who believe in preparing for "A War", as opposed to those who have argued for a far more focused approach towards "The War", or Afghanistan. This debate was central to recent public speeches by the First Sea Lord, Admiral Sir Mark Stanhope, and the Chief of the General Staff, General Sir David Richards.

But apart and aside from the information that came out at the press conference, weighing up the utility of the green paper is more problematic. There are a lot of platitudes – "These are unusually challenging times" – and some contradictions, such as the drive to get rid of wish-list procurement, but still saying that the UK wants to retain a wide spectrum of forces. How this will pan out into the SDR is going to be a very intriguing question.

• Francis Tusa is editor of the London-based newsletter, Defence Analysis.