We have four built vanguard class submarines between 1986 and 1998. These are due to be replaced. Every year they remain in operation costs money to extend their lives (some are slightly newer than others).
Each Vanguard Submarine can take up to 16 US made Lockheed Trident II missile (although actual operating number might be less). Each missile can take up to 12 warheads and each warhead can strike a separate target, possibly hundreds or thousands of miles apart.
16 missiles, 12 warheads is 192 separate targets. Each warhead I believe has around 4 times the power of the Hiroshima bomb (from memory). The warheads and missiles are 100% maintained by the United States, although they do not require US codes to be detonated.
Clearly each Submarine has the power to totally annihilate an enemy state, and that is the point.
Trident is by design, a "second strike" weapon. If you wipe us out, we will wipe you out. The UK Prime Minister gives each submarine commander a letter telling them what to do in the event the UK is wiped out; nothing, join an allied state, if there is one, or retaliate. The UK does not have tactical nuclear weapons (nuclear weapons to be used on the battlefield), so Piers Morgan's suggested that we should Nuke ISIS is stupid (if we needed to, we would ask the US to do it).
In general I believe that Trident makes the use of Nuclear Weapons less likely, just as it is designed to do as Nuclear Deterrent. Deterrent. Noun. a thing that discourages or is intended to discourage someone from doing something.
However there are problems with Trident:
- Are our enemies able to track our submarines?
- Have they hacked them or installed some sort of secret kill-switch?
- All our submarines need to birth every few years. Taking them out whilst docked would be trivial.
- The lack of Nuclear Launch codes makes a warhead going off whilst being maintained, or in another situation, more likely.
- Our missiles and warheads are made by the US. Maybe they too have installed a kill switch, or maybe there is a flaw in the design (see firing the wrong way recently).
- If we elected a Trump/Nixon type figure, would he authorize their use unnecessarily (Deference Secretary Michael Fallon recently spoke about using them).
- Arguably, the biggest threat from Nuclear Weapons isn't from Iran, North Korea or Russian strike... but from a "sum of all fears" scenario where terrorists of rogue national agents simply walk a nuclear weapon into one of our cities. Indeed, realistically, it would actually be stupid for a foreign country to fire nuclear weapons at another country these days. Just walk them in on a lorry....
Trident costs around 0.1% of GDP. Our Foreign Aid budget is 0.7% and NATO minimum Defense budget is 2%
To add to this, Australia are not part of NATO, have no official protection from the Nuclear Umbrella (unofficially maybe they do), they often supply troops to fight wars in the middle east... And they have not been nuked. Does trident really provide useful protection in the 21st century?