David Cameron – who, in case you’d forgotten, leads the Conservative and Unionist Party – made a rare visit to Scotland yesterday. He spoke about defence. His message was clear: an independent Scotland could not expect to win defence contracts from what remains of the United Kingdom. Jobs and expertise, therefore, would be lost. Vote no.

This is, as Iain Martin notes, smart politics. The Nationalists are weakest on those briefs which are the central functions of a nation state: defence, foreign policy and welfare. Cameron, as the British Prime Minister, should make more of this natural advantage. (Incidentally, Alex Massie has an excellent account of the referendum battle. It’s by far and away the best guide to the subject.)

Cameron’s impressive argument was, however, not without fault. He explained how the Union benefited Scotland and vice versa; but there was rather more of the former than the latter. And he sailed in dark waters when talking of the independent nuclear deterrent and its upgrade.

The Scottish National Party has made nuclear disarmament a badge of honour. The Labour Party is no longer synonymous with the Campaign for Nuclear Disarmament. Johann Lamont, leader of Scottish Labour, has resisted pressure from the SNP to drop Labour’s (admittedly lukewarm) support for nuclear weapons. The Labour Party is a big deal in Scotland, perhaps the biggest deal. A curious assumption seems to underlie much of the independence debate: that Scotland would elect the SNP. This is not a foregone conclusion, and that throws doubt on the nuclear question. It may be that a Labour government in Scotland looks at the costs of the deterrent and draws the obvious conclusion; but it is equally possible that the United Kingdom and an independent Scotland would reach agreement on a shared nuclear deterrent. Such an arrangement would benefit the UK as well as Scotland: I’m told that it would be difficult and expensive to construct new facilities outside Scotland to service the independent deterrent, especially a like-for-like replacement of Trident. This is something that Unionists might stress more often; another example of Scotland being ‘very good’ for the Union.

Much of this debate turns on the unresolved matter of upgrading Trident. Cameron has argued that dangers, such as those posed by North Korea, make independent nuclear arms a necessity. NATO is unequivocal: Anders Foch Rasmussen has said that Britain’s independent nuclear deterrent has made the world a safer and more prosperous place. We can assume that he wants such security to continue. Scottish independence would, obviously, affect that balance of power, and not just in terms of nuclear security.

The SNP now favour membership of NATO. This piece in this morning’s Herald says that it is not clear that NATO would welcome Scotland without the bomb. The Herald is surely overstating that point; but it doesn’t seem unreasonable to suggest that NATO would insist on Scotland maintaining a substantial conventional defence establishment, which newly independent Scotland may not be able to provide. Recent military ventures in Libya and Mali suggest that the dynamics of NATO have changed because the United States has shifted its attentions to the Far East. There are greater demands on European powers, and in a restrained spending environment. In the context of Scottish independence, the UK and Scotland could strike a deal similar to that which exists between Britain and France. Or, better still, this might be turned into an argument in favour of preserving the Union because both parties’ defence capabilities and standing within NATO (never mind the world) would be weakened by secession.

The British Prime Minister has made these points before; but he could make them more often and much more loudly.

Tags: David Cameron, Defence, Labour, NATO, Scotland, SNP, Trident