One of the reasons we are told we need to have nuclear weapons is for preventing ‘nuclear blackmail’, or the idea that some country might threaten us with nuclear weapons unless we agreed to do their bidding. It is hard to understand the difference between the theory of nuclear deterrence and the concept of nuclear blackmail, other than the fact that when we use our own nuclear weapons as a threat, that is called deterrence, whereas when another country uses their nuclear weapons to threaten us, it is called nuclear blackmail.
Let us try to imagine a scenario that could be conceivably defined as nuclear blackmail. Let us say there is another Falklands War, only this time the UK has given up its nuclear weapons while in the meantime Argentina has acquired them. Let us further imagine that Argentina has acquired a lot of other sophisticated military hardware and used these to launch another successful invasion of the Falklands/Malvinas. Once again, a British task force sets sail from the UK to fight a war in the South Atlantic, only this time Argentina announces that it will bomb the British task force with nuclear weapons and effectively wipe out the Royal Navy unless it turns round and sails back to the UK.
From the Argentine viewpoint, they are using their nuclear weapons as a deterrent in exactly the way foreseen by nuclear deterrence theory – as a threat against another country which they hope will not need to be carried out because the other country would see it as inflicting unacceptable damage and decide to desist from their planned course of action. From the UK point of view, this would look like nuclear blackmail, since it is a threat using nuclear weapons to try to prevent the UK from doing what it believes to be its right and duty, namely the defence of British territory from external invasion.
What might happen next is anyone’s guess. However, what should happen according to international law is quite clear. First, the matter should be taken to the UN Security Council as a breach of international peace and security. The Security Council should then call on the UK and Argentina to negotiate a peaceful solution to the problem, offering to mediate if necessary. They might ask the International Court of Justice for a ruling on who legitimately ‘owns’ the disputed islands. They might call for an arbitrated settlement or set up a UN trusteeship to put the islands under neutral international control. They might call for a referendum by the islanders to decide their future.
If none of these peaceful means to resolve the dispute were successful, the Security Council would then be authorised to rule who is at fault and to impose sanctions on either or both parties unless they follow the instructions of the Security Council. Even if the Security Council were to rule in favour of the UK being the rightful owner of the islands and victim of an illegal invasion by Argentina, they might still order the British task force back to port until the crisis is resolved.
If all else failed, the Security Council might then authorise the use of force under Chapter VII of the UN Charter to remove the Argentine occupying forces. This would not be a British force but an international force, possibly not even including the UK but perhaps including the US and other South American countries, for instance. Would Argentina threaten the US and other neighbouring countries with nuclear weapons, or would it have deferred to the international community long before it reached that point?
In any case, what this hypothetical example shows is that the threat of ‘nuclear blackmail’ is no more effective in the real world than the threat of nuclear annihilation that is already part and parcel of the theory of nuclear deterrence. In both cases, there is no hard evidence that it ‘works’ nor that it is not more of a deterrent to the country possessing nuclear weapons than to the country it is trying to threaten.