In 2012 an unusual event took place at the SNP’s annual conference: delegates disagreed about something.

The issue at hand was whether a future independent Scotland should join Nato. The narrow vote in favour of doing so was lauded by supporters of the party leadership as a sign that the SNP had at last, after five years running a devolved government, become a serious, mature party that took the defence of the realm seriously.

But to reassure its largely pro-CND membership, the party’s new policy, when published in the white paper that claimed to set out the case for independence during the referendum in 2014, was balanced by a promise to ensure that all nuclear weapons would be removed from Scotland.

Of course, not all Nato members are nuclear powers, but if things had gone Alex Salmond’s way, it would be the first ever instance in which the accession of a new member state would be combined with the removal, not just of its own nuclear defences, but the UK’s too. At a stroke, with no obvious alternative berth for Trident, the Western alliance would be crippled in the eyes of its enemies. 

There were those who viewed the SNP’s 2012 decision to reverse its decades-long antipathy towards Nato as more about public relations for the nationalist movement than about a genuine commitment to international treaties. Those cynics were entirely right.

Moreover, the uneasy compromise the party leadership embraced – removing Trident while endorsing Nato membership – was not only contradictory but denied the reality of exactly how the nuclear deterrent works. Britain’s (and Nato’s) enemies fear to launch an attack on us because they understand that their inevitable, consequent destruction would be too high a price to pay for whatever territorial gains their murderous belligerence had secured.

Advocates of nuclear disarmament have, for more than three quarters of a century, castigated the United States for its atomic bomb attacks on Hiroshima and Nagasaki at the end of the Second World War as a warning of the terrible consequences of this new type of warfare. Yet those attacks would not have occurred had Japan been similarly capable of inflicting the same level of damage on American targets. This threat of “mutually assured destruction” successfully prevented a nuclear conflict during 50 years of cold war, and since.

Yet as the SNP gear up optimistically to hold a second independence referendum before the end of 2023, they continue to pretend that their defence policy is underpinned by some degree of logic. As leaders of an independent Scotland, they would seek to shelter under the umbrella of Nato membership, while denying the alliance the nuclear arms on which it depends to maintain the nuclear balance in an unstable world. 

The invasion of Ukraine has offered the SNP leadership an opportunity to address this fatal contradiction in their own policies. Now that President Putin has revealed himself as a modern day despot with criminal designs on his neighbours’ sovereign territory, will the SNP still insist that Trident should have no role to play in maintaining that fragile balance in Europe?

Perhaps they should now ask themselves how news of the removal of Trident from its British base and from international waters would be received in Moscow. When Nato itself is under more pressure than at any point since the fall of the Berlin Wall, who in the SNP can argue that the West can afford to lose Trident?

Of course, from a nationalist perspective, none of this really matters. The SNP leadership have said all the right things about solidarity with the people of Ukraine in their defiance of the Russian aggressor; many yellow and blue flags have been flown from civic and government buildings to prove their hearts are in the right place. But Scotland itself would be under no immediate threat from an aggressor (no, not even England), so why should it worry too much about the defence of others?

Which is where nationalism always falls down. The SNP policy of having their cake and eating it – membership of Nato while indulging its disarmament-supporting activists – is about its own movement, not about Nato, or even Scotland. Nationalism doesn’t fret too much about conflicts in faraway countries, not unless those conflicts can somehow advance their own domestic agenda. 

The SNP may say they support the plight of Ukraine, but by deliberately proposing a policy that they know will weaken and undermine Nato, they are – no doubt inadvertently – doing the bidding of the man whose tanks are at this minute trundling along the road to Kyiv.