I have often had the pleasure of debating this topic with Jeremy Corbyn, both in and outside the House, but never in either of our wildest dreams or nightmares did we imagine that one day he would end up as leader of the Labour party. It only goes to show the unpredictability of political developments.
After the Falklands war, opponents of our strategic deterrent often pointed out that our Polaris submarines had done nothing to deter Argentina from invading the islands. However, there never was and never will be any prospect of a democratic Britain threatening to launch our nuclear missiles except in response to the use of mass destruction weapons against us. But just because we would baulk at threatening to launch nuclear weapons except when our very existence was at stake, that does not mean that dictators share our scruples, our values or our sense of self-restraint.
An example from history will do. Following the horror of the poison gas attacks in the first world war, it was widely expected that any future major conflict would involve large-scale aerial bombardments drenching cities and peoples with lethal gases. Why did Hitler not do that? Because Churchill had warned him that British stocks of chemical weapons greatly exceeded his own, and that our retaliation would dwarf anything that Nazi Germany could inflict. Poison gases are not mass destruction weapons, but nerve gases are, and Hitler seriously considered using them against the allies in 1943. He did not do so because his principal scientist, Otto Ambros, advised him that the allies had almost certainly invented them too. In fact, we had done no such thing and were horrified to discover the Nazi stocks of Tabun nerve gas at the end of the war. That was a classic example of a dictator being deterred from using a mass destruction weapon by the mistaken belief that we could retaliate in kind when actually we could not. Such examples show in concrete terms why the concept of deterrence is so important in constraining the military options available to dictators and aggressors.
I shall briefly list the five main military arguments in favour of continuing the specific British policy—pursued by successive Labour and Conservative Governments—of maintaining, at all times, a British minimum strategic nuclear retaliatory capacity.
The first military argument is that future military threats and conflicts will be no more predictable than those that engulfed us throughout the 20th century. That is the overriding justification for preserving the armed forces in peacetime as a national insurance policy. No one knows which enemies might confront us between the years 2030 and 2060—the anticipated lifespan of the Trident successor system—but it is highly probable that at least some of those enemies will be armed with mass destruction weapons.