A Trident submarine leaving its base in Scotland.In 2014, a referendum will be held in Scotland to decide whether it should become a sovereign state or remain within the United Kingdom. A yes vote would result in the world witnessing the breakup of a nuclear-armed state for the second time.

The Soviet Union’s collapse in 1990 raised the specter of nuclear proliferation and the loss of central control over assets and expertise. A British breakup would not give rise to similar threats. Instead, the question is whether the successor state, presumably the UK shorn of Scotland, could retain its nuclear deterrent. Although the weapons system might survive political fragmentation, a breakup could result—unlike for Russia—in the UK’s nuclear disarmament.

For fifty years, the UK’s nuclear-armed submarine force—first Polaris, then Trident—has been operated out of Faslane and Coulport on Scotland’s west coast, near Glasgow. This imposition, as it has often been seen in Scotland, has contributed to the rise of the Scottish National Party (SNP), which presently heads the regional government in Edinburgh (having the majority of seats in the Scottish Parliament that was reestablished in 1999). It has pledged to remove all nuclear weapons from an independent Scotland, insisting that the London government will have to find alternative bases in England or Wales. But there are no such alternatives. Although an equivalent to Faslane, where the submarines are berthed, might be developed at considerable cost, the base at nearby Coulport is irreplaceable. It is there that missiles and warheads are stored and loaded on the submarines. Evicting Trident from Scotland therefore amounts to closing down the UK nuclear deterrent.

Could a newly established Scottish state implement this policy? After a vote for independence, international recognition and agreements with London on a range of issues, including economic relations and rights over North Sea oil and gas fields, would be the highest priorities. Forcing the nuclear deterrent’s abandonment would hardly encourage London’s cooperation, let alone that of Paris, Washington and other capitals. That said, it would be politically hard for a sovereign Scotland to concede to Trident’s presence in perpetuity.

In addition, the London government could not impose, without international protest, nuclear weapons on an independent Scotland determined to become both a nuclear-weapon-free country (like Denmark and Norway within NATO) and a non-nuclear-weapon state party to the Non-proliferation Treaty (NPT). Subject to control over weapons being retained, the NPT allows nuclear-weapon states to operate their forces out of the territories of non-nuclear-weapon states, even though operating allnuclear forces out of another country, as in this instance, would be unprecedented. Without the host country’s willing consent, however, the situation would be neither manageable nor legitimate.

A compromise can be imagined in which the Scottish bases would continue to be used until the current fleet of four submarines becomes obsolete in the 2020s and 2030s, on the understanding that replacement boats would have to go elsewhere. But this is not a solution if there are no other conceivable bases at home or abroad. Deploying the UK’s nuclear force out of French or American bases—an idea occasionally floated—is politically implausible. Alternative delivery systems that might allow relocation to England, such as air-launched cruise missiles, are also not favored by the Ministry of Defence. As a consequence, either the Scottish government and people would have to resign themselves to Trident’s stay in Scotland, in return for concessions on other core issues, or the London government would have to abandon the deterrent.

Current opinion polls predict defeat for the Scottish nationalists in the referendum. But defeat would likely still be followed by a more extensive devolution of powers to the Scottish Parliament. The issue of self-government will not go away, especially if London’s malfunctioning institutions—the union’s troubled heart—are incapable of reform. Whatever happens in 2014, the UK’s possible breakup will henceforth be an issue for military planners, especially when considering long-term investments and deployments like Trident.

The fate of the British nuclear deterrent depends on more than the union’s future. Heavy spending on Trident’s replacement is due to begin in a few years’ time. There is already concern in military and political circles, amidst questioning of the deterrent’s relevance to Britain’s future security, that Trident will squeeze out more essential defense investments. Irrespective of the referendum on independence, a debate about Trident’s cost and value to the UK is likely to reopen on a very different political landscape than 2007, when the UK Parliament voted decisively—blind to the union’s fragility and anticipating endless prosperity—to replace Trident.

Trident’s value will be assessed in more than security terms. From the outset, the UK’s nuclear force has been used to express great-power aspirations. Along with permanent membership on the UN Security Council, it has protected the UK’s position at the high table. It has also, together with intelligence sharing, helped to anchor the “special relationship” with the United States. Fearing international diminution of Trident’s perceived prestige value if Scotland breaks away, London’s—not Edinburgh’s—desire to preserve Trident may increase just as its economic costs are becoming hard to bear.

William Walker is professor of international relations, University of St Andrews, Scotland. He is author of A Perpetual Menace: Nuclear Weapons and International Order (2012) and coauthor with Malcolm Chalmers of Uncharted Waters: The UK, Nuclear Weapons and the Scottish Question (2001).

Image: JohnED76