I read on facebook recently a post by Alan Storkey (sorry I can't link because I can't find it any more!) on reasons why replacing trident is a bad idea. They were great thoughts, but one resonated with something I have thought for a while, and for me is the main reason that Trident is a bad idea.
The problem is that Trident - and all nuclear weapons capability - belongs to a different age of warfare. I am not saying that 40 years ago it was valid and acceptable, just that then there were different reasons to challenge it. But the world today is different.
The major threats on the world stage today are terrorist groups like IS. The majority of the conflicts across the world are not nation-on-nation, as they were for much of the last century, they are faction on faction, organisations like IS who are fighting for recognition and a cause. Groups like Boko Haram in Africa and the drug barons in Mexico are involved in much more typical conflicts today than was the case.
And, of course, Trident - any nuclear weapon - is of no use against them. How could we use any of them against IS? They do not have a geographical claim, so the use of such weapons - which are indiscriminate across a geographical area - is pointless and dangerous.
"But we have to have them, to protect ourselves against other nuclear nations". This has been the argument for decades, and yet it is flawed. As noted above, conflicts today are not against other nations. The likelihood of, say, Iran attacking us with a nuclear weapon is extremely remote - they may not like us, but that tactic would be so abhorrent that they would never utilise it. Because they are a geographical nation, they would be destroyed in a range of ways that would not require a nuclear strike back.
"They are a deterrent against anyone using nuclear weapons against us". The thing is, let us suppose that IS had nuclear capability. Let us suppose, horror of horrors, that the Paris attacks had been nuclear. Would we then use our nuclear weapons against them? Of course not, because they are not a geographically located group. It is groups like IS with nuclear capability that is the biggest danger, but even if they did achieve that, out deterrence would not stop them and out defence would not be appropriate to use. So what is the point?
I hope against hope that we never see another nuclear weapon deployed. But if it is, it will not be a nation using it against another nation. The response will not be more such weapons. Nations arming themselves with nuclear capability in the 21st century is an anachronism. We would all be safer if we had none of them around.