What is Trident and Why Do We Need It?

By Rich Wordsworth on at

In the weeks and months leading up to the election, Trident was fleetingly promoted from simmering, 25-year-old contention to the centre of British politics. The issue was not Britain’s current system of at-sea nuclear deterrence, but rather, its replacement. All major parties barring the SNP were in agreement: Britain needs a new generation of missile submarine to replace our four ageing Vanguard class missile boats, at a cost that will, over the course of the renewal, be measured in tens of billions of pounds.

That such costly pledges were made in a time of economic austerity only buoyed the controversy. As the system’s replacement will be paid for in full by the Ministry of Defence, Britain’s conventional armed forces will see money that could have otherwise been spent elsewhere earmarked for Trident. Coupled with a growing cynicism that deterrence is effective in the modern age – you can’t fight insurgents or terrorists with nuclear missiles – and we are left with the multibillion pound question: Is Trident something we really need?

What is Trident?

Britain’s nuclear deterrent is unique among the nuclear weapon states. We are the only country to maintain an arsenal entirely built around the principle of ‘continuous at-sea deterrence’ (CASD). We have no missile silos, no nuclear-armed bombers and no ground-based launchers. While Britain’s arsenal is, in pure numbers, far smaller than America or Russia, it remains a credible deterrent because so long as one of the four submarines that carry the Trident missiles is at sea, nobody knows where a British nuclear retaliation will come from.

“Submarines are a curious thing because the whole point of a submarine is that it’s a floating missile base, somewhere in the ocean, and no-one knows where it is,” says Tim Collins, a final-year doctoral candidate at King’s College London researching Trident.

“At any given time, allegedly, the only people who know where a Vanguard submarine is are the people on the submarine – specifically the captain, the [executive officer] and whoever is in charge of navigation.”

The Trident system comprises the submarines, the crew and the Trident missiles, which can be launched from below the surface and hit multiple targets at a range of between 8000 and 11,000km (depending on the number of warheads fitted to the missile – more warheads, more weight, less range). Once a Trident missile clears the surface, it fires in an arc into space, where the warheads separate from the main body of the missile. These warheads can then be independently targeted, potentially allowing a single Trident missile to hit up to twelve targets.

“The maximum complement four submarines could have would be 64 missiles, with 768 warheads,” says Collins.

“That’s pretty big. That’s 16 missiles per submarine, and each missile can have 12 individual warheads… In practice we’ve never deployed that many. Trident came online as the Cold War was ending, and since then we’ve made further reductions… probably due to changes in strategic environment. The Cold War ends, do you really need this many [missiles and warheads on standby]?”

what is trident

Do We Need Trident?

In the event that Britain were attacked by another country using nuclear weapons, it is the Prime Minister (or if he is incapacitated or has been killed, an appointed deputy) who would give the order for the submarine to retaliate. An encrypted message is sent, the Vanguard captain and his executive officer retrieve codebooks from their safes, and then must famously turn keys simultaneously to fire the missiles - preventing any one person from starting Armageddon. But there’s another advantage to carrying a nuclear deterrent on a submarine: even if Britain were completely destroyed before orders could be given, the captain of the submarine has what is known as the ‘letter of last resort’.

“One of the first duties of a new Prime Minister is to write a letter that goes on the submarine [explaining] what to do if Britain has been destroyed,” says Collins.

“[The Prime Minister] writes the letter, the letter gets sealed, four copies are taken by the Ministry of Defence to the submarines, and they’re locked in a safe only to be opened if Britain has been destroyed.

“No-one really knows what the contents are except the Prime Minister, but people guess one of four things: find the Americans who have survived and join up with them; retaliate immediately at whoever has attacked Britain; sail to Australia, so you go somewhere that’s survived and find more information; and the other one is use your own judgement.” Collins pauses. “Which I think must be a very unhelpful thing for a captain. Britain’s been destroyed, you open the letter [and it says] ‘make your own mind up’.”

A Costly (But Sensible) Evil?

If Britain is going to have a nuclear deterrent, Trident is, according to Collins, our best option.

“It’s the safest, it’s the most credible, you can’t find it, you can’t shoot it down, it is destructive enough that you can target enough cities and no-one is going to say, ‘maybe I’ll bomb Britain’,” he says.

But if Trident is so effective, why replace it in the first place? According to Collins, there are two reasons: one immediate, one longer term but equally problematic.

The most pressing concern are the reactors on board the Vanguard submarines. British submarines (both the Vanguards and the attack submarines we use to sink enemy ships and stalk enemy nuclear subs) are powered by nuclear reactors that let a submarine sail for decades without the need to refuel. The problem is that once the reactors do run out of power, the systems are so integrated with the rest of the submarine that the whole vessel must be replaced - you can’t just swap them out like batteries. Once the reactor goes, the submarine goes as well, and designing and building a replacement takes years.

The second reason is that the technology a potential aggressor might use to detect a submarine is advancing all the time – and if an enemy knows where a Vanguard is when it’s at sea, the submarine can be sunk as part of a first strike. Britain is, says Collins, very, very good at making silent submarines, but as he puts it, they “won’t remain so perfectly silent forever.”

what is trident

Disarmament: An Unlikely Ethical Alternative

All this presupposes, however, that we want a nuclear deterrent in the first place. Costs aside, there are valid reasons to oppose Trident’s renewal. For one, there’s the not unimportant ethical question of what wiping out another country’s cities in retaliation does for us if we’re all already dead. For another, giving up nuclear weapons would set a powerful example to other countries that might be considering developing, upgrading or expanding their own arsenals. Finally, there is the question of Britain’s commitments as a signatory to the Non-Proliferation of Nuclear Weapons Treaty (NPT), article VI of which obligates Britain “to pursue negotiations in good faith on effective measures relating to the cessation of the nuclear arms race at an early date and to nuclear disarmament.” While Trident’s successor is often described as a ‘like-for-like replacement’, modernising our fleet of invisible nuclear launch platforms could be understood as obeying the letter, rather than the spirit, of the NPT.

So why the near unanimous support for Trident among Britain’s major political parties? Because, Collins suggests, there is a very big psychological difference between arguing for disarmament as a politician and arguing for it as a member of the public. If you’re a politician, this is one of the decisions you absolutely do not want to get wrong.

“There has always been a problem about who moves first,” says Collins of disarmament and NPT’s ultimate goal of a world without nuclear weapons.

“I think lots of [politicians] are sceptical that Britain will ever use its nuclear weapons in the future. A scenario where Britain is isolated, there’s no NATO, someone is threatening us with nuclear weapons, and only our nuclear capability is saving us… That’s a very narrowly defined set of circumstances that may never happen.

“However, if you’re a politician, and your job is ultimately the security of your people into the future, and no-one can tell you what the future looks like… If you’re suddenly in charge of that decision, and if in 30 or 40 years Britain needed this capability and you were the guy who voted to get rid of it… That’s a very difficult calculation to make.

“I think a lot of critics should consider what it’s like to sit in that seat,” he says. “What if this thing is necessary, and what if we got rid of it?”

Tim Collins is a final-year doctoral candidate in the War Studies Department at King’s College London and a member of the Centre for Science and Security Studies research group. He is researching the British nuclear experience and small nuclear arsenals.

Image Credits: Vanguard class submarine / Trident II missile from Wikipedia, Woman holds a placard from Shutterstock