Who is Trident meant to deter - and will it?

Who is Trident meant to deter - and will it?

UK Trident warheads have not been targeted and missiles have been at 'several days notice to fire' (HMG website) for over 20 years (2019).

The fundamental questions of what are the threats and would Trident be used against them lies at the heart of the discussion. So first let us look at the threats.
Long range nuclear missile strike against UK

There are only five  nations with the resources to launch a long range nuclear strike - Russia, China, USA, India, France. The latter three can be discounted immediately.

Russia. Despite all President Putin's blustering and bravado, his ambitions reach only to securing his borders by regaining control of countries that were former Soviet satellites. Having annexed Crimea, there is a realistic fear that this could be extend to e.g. Ukraine, Estonia and Latvia. However, there has been no consideration at all given to using Trident.

China is similarly concerned with extending its reach locally in the South China sea e.g. Spratley Islands, but has no plans to impose themselves worldwide other than commercially - including building UK civil nuclear power plants!

Rogue States. It can rightfully be argued that there are existing - and may well yet emerge -  Rogue States which might threaten to use a nuclear device in some way include:

Iran until very recently headed the list. It had a strong anti Western political attitude and was almost certainly aiming to develope nuclear weapon technology. A combination of trade sanctions and political manoeuvring has, for the moment, brought them in from the cold with an agreement to halt nuclear weapon research. Some think this is a temporary postponement of the problem

North Korea is the only such Rogue State at present that we know possesses the technology to test atomic bombs - considerable doubts exist over their stated H Bomb test in January 2016 -  but they definitely do not yet have the missile or war head technology to carry a nuclear weapon beyond a few hundred miles - if that. Their ambition to be a nuclear power is almost certainly so as to have nuclear 'muscle' with which to hold other countries to some sort of ransom and has as much to do with egocentric dictatorship as any strategic plan for territorial gain. However they definitely come into the category of a Rogue State to be feared of.

Daesh (aka IS/ISIL) purports to be a State but more rightly is a collection of extremist religious fanatics who undoubtedly are sufficiently motivated and unpredictable to be capable of using nuclear weapons if they could get hold of them.

It is impossible to exclude the emergence of another Soviet type power seeking world domination that would merit a return to the policy of Mutually Assured Destruction. However, to retain a weapon system of this complexity and cost against the possibility that one might emerge is a form of insurance requiring deeper pockets than the UK possesses. It can only be afforded if other costs savings are made. This is discussed further in other sections.

Could/would Trident be used against Rogue States? The answer is clearly No because it has not been anywhere near consideration in the cases above.

Why is this? Their proximity to other nations makes it impossible to decide where even a low yield nuclear device could be safely exploded. Nuclear missiles can be delivered with pin point accuracy but as their devastation is totally indiscriminate then large sections of an 'innocent' population would be taken out as well. The toll would be entirely unacceptable.  The lingering nuclear radiation fallout would also make it impossible to occupy the territory for military or disaster relief purposes for a long while after.

In view of the fact that deterrence lies in the mind of your adversary not your own mind, and so if your adversaries  do not think - or care - that it will be used then it is no deterrent. In fact, on 24 March 2002, Geoff Hoon, the then Defence Secretary, stating in a BBC interview that the UK was prepared to use nuclear weapons against ‘rogue states’ ...‘What I cannot be absolutely confident about is whether or not that would be sufficient to deter them from using a weapon of mass destruction in the first place.’