DEFENCE is one of the most contentious issues in the independence debate, with the fate of the naval bases at Faslane and Coulport – and the future of the British nuclear weapons sited there – dominating discussion so far.

With around 6500 associated jobs in an area with few other large employers, there is pressure on the Yes campaign to commit to maintaining the bases. On the other hand, the independence-supporting CND is determined to get rid of nuclear weapons – not just in Scotland but also in the rest of the UK (RUK).

Much of the debate has operated in the realms of fantasy. There has, for example, been speculation over the fate of Scotland's historic regiments, despite the fact this issue was settled almost a decade ago when the British army established the Royal Regiment of Scotland. The old regiments no longer exist in a meaningful way, they are nameplates on doors, not real military units. All officers, enlisted men and non-commissioned officers in the Royal Regiment are rotated regularly between the battalions during their careers. They are not lifetime members of the Black Watch or the Royal Highland Fusiliers. Moreover, research has shown that an independent Scottish army, if it were sensible, would maintain two separate brigades. One could be active and one reserve, or there could be elements of active and reserve in each, but it would be the dual structure that would make the most sense. Trying to maintain a military structure based on regiments that were established during the British Empire in an independent Scotland is about as sensible as trying to re-establish the Raj.

The main problem with this debate is that it has tended to focus on what has happened, not what should realistically happen in the future – the fate of the Clyde shipbuilding industry, and of military facilities at Rosyth, Lossiemouth, Leuchars and elsewhere being cases in point. That the Yes campaign would want to reassure those with a stake in Britain's military industrial complex is understandable, but the result is a sterile debate that they almost certainly cannot win. It leaves independence campaigners proposing a "Mini-Me"-like defence structure that would neither be large enough to convince those who are worried about jobs, nor creative enough to please those who see independence as a way of defining a new future.

The last thing an independent Scotland should want to be is a shrunken version of the UK. Scotland would be a small, European country with a strategic location and one very important strategic asset – North Sea oil. It would need to create a military which adjusts to this new reality and which could co-operate with similarly sized states such as Denmark, Norway and the Netherlands. This co-operation would be crucial because while we in Scotland like to think a major conflict is impossible, the truth is that it is merely unlikely. Norway and Denmark are both concerned by the restructuring and re-equipping of Russian military. Norway shares a border with Russia and the two countries have competing claims to the oil-rich waters of the Arctic.

This is one of the reasons that there is a great deal of scepticism in Europe about Scottish independence. The UK is seen as an important and reliable defence partner, whose relationship with the USA gives it great significance within Nato. Deconstructing the UK, therefore, threatens to create a new and less stable world for many European countries, and an independent Scotland would need to recognise this and construct its new military forces in as co-operative and sensible a way as possible. Scotland would not need a large, multi-purpose military to play a major role in military interventions overseas, it would need a small, highly professional military that could carve out a useful niche in the Nato defence structure.

If Scotland stayed in Nato, which I believe it must for political reasons, its security internationally would be guaranteed. As a member of Nato it would have to carve out a specific role in the alliance, similar to that of Norway (which specialises in anti-submarine warfare) or Denmark (which specialises in mine sweeping). In terms of home security its greatest strategic assets right now are the oil fields of the North Sea, so it would have to be able to project force, both naval and air, in that direction.

This would cost money, but not as much as the SNP plans to spend. Its website contains very few specifics on defence, but one is that the party will support an annual defence budget starting at £2.5 billion. This figure is actually too large, or too small. It's not enough to maintain everything that is in Scotland today, but it's actually more than an independent Scotland would need to spend to defend itself. Looking at close-comparator Nato countries, it would seem that a reasonable percentage of GDP to spend on defence is 1.4%. This is what Denmark spends, while the Netherlands spends 1.3% and Belgium 1.1%. As an independent Scotland would have a GDP of approximately £125bn, it would be reasonable to spend some £1.75bn a year.

For that amount Scotland could defend itself and be integrated well within Nato. It would have the two-brigade army structure. A Scottish navy actually has an excellent model to follow: Denmark's navy is based around three frigates and a number of smaller craft. It is divided into two squadrons, one directed towards domestic patrols and protection, and the other to serve with Nato. A small part of the present Royal Navy would allow for this kind of division, based on existing Type 23 frigates. There could be an international/Nato naval force based at Faslane and a domestic force somewhere on the east coast, perhaps Rosyth, from where it could quickly reach the North Sea oil fields.

The one really difficult hardware question that would face an independent Scotland would be the size and composition of its air force. Modern aircraft are extremely expensive to purchase and maintain. Scotland's closest-comparator Nato countries have air forces based around F-16 squadrons. It is unlikely Scotland would want to spend much money buying new aircraft, so it would be better served negotiating a share of the present RAF. Most sensibly one of the Typhoon squadrons at RAF Leuchars could be used to create the nucleus of a Scottish air force.

All of this could be maintained for £1.75bn per year. The political reality, though, is that it would call for considerably fewer or smaller military facilities than currently exist. And this is where the Yes campaign could be far more creative than it has been so far. Instead of trying to maintain the fiction that an independent Scotland would keep anything like the present force and base structure, it could be stated that the best way forward would be to manage the change. For instance, one could take the £750m per year saved on defence spending from the proposed £2.5bn budget to create a defence transition fund for the first 10 years of independence. This would give an independent Scotland £7.5bn to address the economic effects of declining defence spending, for example by regenerating or reconstructing areas affected by the loss of military facilities. Most of that would have to be spent in the Glasgow/west of Scotland area, since without intervention the west would lose out. Even if Faslane/Coulport were the home of half of the Scottish navy and one of its infantry brigades, it's hard to see how the bases could support more than half the existing number of jobs.

Moreover, and this needs to be faced openly and honestly, warship building on the Clyde would be damaged by independence. For political reasons, RUK would not build its warships in Scotland.

The defence transition fund could, however, provide a post-independence economic future for these areas that would be damaged, offering hope to those now rightfully nervous. It would avoid the economic losses that affected the Dunoon area after the closure of the American submarine base on Holy Loch. As well as the Glasgow/Clyde area, the fund could help the Inverness region, since it is unlikely that Lossiemouth and Fort George would both be maintained – unless Leuchars and Penicuik were closed.

There is no reason that all major Government ministries need to be based in Edinburgh, and the Yes campaign could campaign on basing an independent Scotland's defence and security ministry in Glasgow. This would help offset the geographical economic disparity that would be exacerbated by independence. Since devolution, Edinburgh has prospered, with property prices rapidly outstripping Glasgow's. Were a fully-fledged independent state established in the capital, with its concurrent bureaucratic and international structures, Edinburgh would benefit significantly.

Together, an annual defence budget of £1.75bn, plus £750m of transition funding, and a plan to disperse elements of the governmental structure of the new state would leave Scotland secure, provide economic security and more just distribution of Government resources.

Internationally, Scotland's defence policy would have to be based around Nato membership and a moderate anti-nuclear policy. The effects of leaving Nato could be disastrous for a newly independent Scotland, creating an obstacle to EU membership. It is important to remember that most of the countries that would matter for an independent Scotland have little desire to see the UK break-up. Countries such as France, Spain and Italy, which have their own separatist movements, are deeply unhappy about the precedent this would set. Other countries, such as Germany, Denmark and Norway (admittedly not an EU member), see Nato and the Atlantic Alliance with America as the cornerstone of their security. The Germans would probably be less opposed to an independent Scotland than France. However, if they believe an independent Scotland would leave Nato, thereby weakening American commitment to European security, the Germans would offer the new country no support. All those countries right now see the UK, as part of Nato, as a very reliable and important defence partner. An independent Scotland that was detached from Nato, would be a different entity.

If Scotland chose to leave Nato, it would hand a huge amount of power to the RUK in every aspect of the independence negotiation process. For instance, it is not obvious how and where the sea boundaries between Scotland and RUK would be drawn – a very important issue which has received almost no comment. The RUK is already in an extremely powerful position to achieve its goals in the negotiations with Scotland; by rejecting Nato, Scotland would find itself devastatingly isolated.

However, by accepting the benefits of Nato membership, Scotland could craft a defence policy that serves the new nation's needs. It could even be a non-nuclear country, and decide not to develop or maintain nuclear weapons. It could not, however, ban nuclear weapons from Scottish waters, in the way that New Zealand does. Neither could it expressly forbid Nato from bringing in nuclear weapons in the future.

As for removing the nuclear weapons already in Scotland, that would need to be negotiated with the RUK. Scotland should not demand immediate removal, since attempting to dictate the RUK's nuclear policy would almost certainly lead to disastrous setbacks in other areas of the independence negotiation, leaving Scotland friendless in much of Europe. However, if Scotland set a reasonable timeline which would allow the RUK to decide how or whether they wish to keep their nuclear deterrent, this would certainly improve Scotland's strength in the negotiation.

So, being sensible and creative, Scotland could craft a defence policy that made the independent country secure, provided a reasonable and balanced military capability saved money and helped ease the transition for areas that would be economically hurt. At the same time, Scotland could negotiate from a position of some strength and end up both as a member of Nato and a non-nuclear country. Such a policy would also invigorate the present debate over defence and independence.

Right now the No campaign, with some justification, attacks the Yes campaign for being too vague. This policy would mean that the No campaign, which has so far avoided its major weakness in defence issues, would have to spell out what the threats would be to an independent Scotland and why the country would be somehow less secure outside the UK than in. Only this way can we have the debate over defence that the country truly deserves.

l Dr Phillips O'Brien is director of the Scottish Centre for War Studies at the University of Glasgow. Originally from Boston, USA, he has given evidence to Westminster's Scottish Affairs Committee on the defence models that could be pursued by an independent Scotland. His books include Technology And Naval Combat In The 20th Century And Beyond, and The Anglo-Japanese Alliance.