The authentication of North Korea’s nuclear test by the American authorities last week confirmed that we are in a new and disturbing atomic age.

No longer is the use of nuclear weapons as a means of resolving international disputes made nigh inconceivable by the international balance of terror.

We now have to get used to the fact that weapons of mass destruction are probably going to be used. Kim Jong-II is just the kind of desperate, nothing-to-lose political leader who might actually see a first strike as the best way of achieving political objectives.

This alters the nuclear equation in a way which will be troubling both to nuclear disarmers and to advocates of deterrence. We can expect Gordon Brown, for example, to start talking about how, in a dangerous world, it would be irresponsible to give up or fail to renew Trident.

On the other hand, Alex Salmond, the SNP leader, made his contrary view abundantly clear at the SNP conference in Perth. “We will never abandon the policy of unilateral nuclear disarmament,” he said, ensuring that this will be a defining issue in May’s Scottish election.

Labour are already claiming that this anti-nuclear declaration is a measure of the irresponsibility of the SNP leader – a sign that he hasn’t lost his capacity to let his rhetoric run away with him. Like as his denunciation of the bombing of Belgrade as “unpardonable folly” in 1999, they will say, his unequivocal declaration for nuclear disarmament confirms that he cannot be trusted to run a government, even a devolved one.

Trident, like all defence, is of course a reserved matter under Westminster control, and the Scottish parliament has no say. But Labour thinks Salmond will use the nuclear issue as a way of fomenting constitutional strife between London and Edinburgh.

As well he might. But this strife may not be a very difficult to foment. There has long been a majority in Scotland opposed to the presence of Trident nuclear submarines on the Clyde.

Time was when Labour MPs were part of the anti-nuclear consensus. Shortly before the election of the Scottish parliament in 1999, BBC Scotland reported that a majority of Labour candidates for the Holyrood elections were avowed unilateralists.

It did not take them a very long time to become un-avowed, of course, as often happens when an opposition party enters government.

Could the SNP, if they became the lead party in a Scottish coalition, follow Labour and abandon unilateralism? Unlikely. Labour MSPs gave up their principles to avoid confrontation between Westminster and Holyrood. The SNP would see things differently, wishing to point up differences with London, not paper them over.

The nuclear issue is a key one for Scotland, and not just in the arena of defence. The collapse of the price of shares in British Energy last week, following news of the latest cracks in the tubes of Hunterston nuclear power station, has cast in stark relief the north-south divide in electricity generation.

Electorally, Scotland could well find itself voting for a nuclear-free zone after May. The likely coalition partners – Greens, LibDems and the SNP – are all against nuclear power and nuclear defence, at least as regards Trident renewal. Though, as always, there is a question about the LibDems.

However, the big question remains: is unilateralism any longer a credible position given the belligerence of Pyongyang? In the past, unilateralists condemned Trident on the grounds that, since the end of the Cold War, there was no credible use for a weapons system designed to obliterate Russian cities. Al Qaeda is hardly going to be deterred by multiple-warhead, intercontinental ballistic missiles.

Well, now we have a country, North Korea, which could pose a threat, if not to the West, then certainly to the peace of south-east Asia. Can we allow a tyrant like Kim to use nuclear weapons to achieve his insane regional ambitions?

The short answer is that Trident renewal doesn’t deter; it just makes proliferation more likely. Our hypocrisy over the Nuclear Non-Proliferation Treaty has left the West in a weak moral position to condemn countries seeking to acquire nuclear status. The only way to achieve nuclear arms reduction is to enter into meaningful disarmament negotiations. As indeed first minister Jack McConnell proposed at Question Time last month.

But the immediate problem for Scotland is that we are in the front line of a war we never chose. It is the insane military adventurism of the Blair/Bush axis which has not only placed Britain in the front line of international terrorism, but placed Scotland in the front line of nuclear confrontation.

Scots may have reluctantly accepted the burden of having nuclear submarines in the Clyde in the days when there was a serious global threat from the Soviet Union. But times change. Are we to become a target because of the stupidity of people like George W Bush, or Gordon Brown if he chooses to follow him?

No, I suspect the Scots will become even less content with the nuclear status quo. Nor will the Scottish media leap to the defence of a weapons system which is so clearly unfit for purpose.

For the first time in 20 years unilateralism is a key issue in British politics. The other big question is: what will the Americans do if Salmond wins?