By Malcolm Chalmers

If Scotland were to insist on Trident’s removal from Faslane before the UK could relocate to another operating base safely, its chances of joining either Nato or the EU would be slim. The UK would find it very hard to maintain an operational nuclear deterrent. As one of its first acts as an independent state, Scotland would have decided that one of its immediate priorities was the disarmament of the UK against the latter’s wishes. 

If Scotland were nevertheless to insist on rapid removal, most Nato members would view a membership application with considerable suspicion. This reluctance would likely spill over into the EU, most of whose members participate fully in Nato’s nuclear planning group.

At a time when Western unity is so important because of Russia’s aggression, few would want a Scotland which might disrupt a hard-fought consensus on Nato nuclear policy, and few would trust reassurances that a Scotland that was so committed to expelling nuclear weapons from its own territory would not also want Nato policy to change fundamentally. 

Over time, opinions might soften in some parts of the alliance as the risks of leaving Scotland outside the European mainstream became more evident. Even then, Scotland could not join Nato without active UK support for doing so – and, given its growing security role, the same would likely also be true even of the EU. 

Nor would the prospect of expulsion be easily accepted in pre-separation talks. The UK would have several cards in its hand that it could use to persuade Scotland to change its mind – most notably in the extent of economic co-operation it was prepared to accept.

Precisely because such potential risks are so clear, however, it is unlikely that those leading post-vote negotiations would gamble Scotland’s independent future on such a step. 

History tells us that the fate of newly-independent states is strongly dependent on the conditions under which they are created. In the most likely independence scenario – a free but narrow vote, the results of which are accepted by all concerned within Scotland and in the UK – there would be strong support for preserving a special constitutional relationship with the UK, together with as much of a single market as is compatible with EU membership, including a common travel area.

This is a model that would be closer to the forms of independence chosen by Canada, New Zealand and Australia – rather than the more disruptive separation of the Irish Republic.

It is also one that might, in time, involve levels of co-operation on defence and intelligence every bit as deep as those the UK has with other members of the Five Eyes – Australia, Canada, New Zealand and the US. Crucially, it could open the way for extensive UK support for Scotland’s military defences, with UK and Scottish forces working closely together within a broader Nato framework. 

Yet such a model would only be possible if Scotland kept the UK’s submarine force at Faslane, at least until a new base could be built (likely in the south-west of England) – a process that likely would take more than a decade to complete.

On the other hand, if Scotland were provisionally prepared to accept longer-term (though not indefinite) Trident basing, it would have an immensely strong bargaining card. By making the UK dependent on its goodwill for retaining its nuclear deterrent, Scotland could marginalise those – of whom there could be many after a Leave vote – who would be tempted by the prospect of taking a more punitive approach.

The NPT, not the TPNW

Finally, to be fully accepted as a member of Nato, Scotland would have to fulfil further conditions in relation to its stance on nuclear weapons. The experience of Sweden and Finland, due to become the latest Nato members soon (Turkey permitting), provide an important example here.

While Sweden attended the recent conference on the Treaty on the Prohibition of Nuclear Weapons, it did so only as an observer, and instead supported a step-by-step approach to disarmament through the Non-Proliferation Treaty.

Like Sweden, a Scotland seeking to join Nato would have to accept that full membership of the TPNW is incompatible with membership of a nuclear alliance – the relevance of which has been made all too clear by Russia’s nuclear posturing in recent months.  

If Scotland wanted to be a “normal” European state, it would therefore have to accept the full nuclear implications of what Nato membership means. If it were to do so, and was supported by the UK, it would likely be welcomed with open arms.

If, instead, Scotland insisted on the immediate expulsion of Trident, it would likely be seen as yet another problem for European security, rather than part of the collective effort to address those problems.  

Professor Malcolm Chalmers is deputy director general of the Royal United Services Institute in London