Trident: How Important is an Independent Nuclear Deterrent?

by Benjamin Studebaker

Britain’s leader of the opposition, Jeremy Corbyn, has declared his opposition to the use and possession of nuclear weapons:

Specifically, he wants to discontinue Britain’s Trident nuclear program. Trident consists of four submarines, 58 Trident II D-5 ballistic missiles, and 160 thermonuclear warheads. All together, Britain has the 5th largest nuclear program in the world:

How important is this program to Britain’s security? On this issue, I think both Corbyn and his critics have oversimplified matters a bit. The role nuclear weapons play is more complicated than both hawks and doves typically acknowledge.

The argument for nuclear weapons relies on their deterrence power. Countries are unlikely to attack nuclear-armed states because of the risk that these states might respond with nuclear weapons. Even if the chance of a nuclear response is very small, the amount of damage a nuclear attack would cause is enough to deter countries from engaging in hostilities with nuclear powers. In essence, nuclear weapons make the potential costs of war too high for most potential aggressors to realistically contemplate.

Deterrence is also achievable with conventional military forces–countries are unlikely to attack countries with large conventional armies even in the absence of nuclear weapons, because these conventional armies may be very difficult to defeat in battle. But because a nuclear arsenal can quickly and easily cause catastrophic damage, its deterrence value is considered to be much higher. Before nuclear weapons, countries routinely went to war with each other, even when both sides possessed large conventional military forces. In the 70 years since nuclear weapons were first acquired, there have been no full scale wars directly involving two or more nuclear-armed states despite significant hostility among them, particularly between the USA and the USSR. In the 70 years before nuclear weapons were acquired, there were a number of wars between powerful states with large conventional military forces (e.g. the world wars, the Russo-Japanese War, the Russo-Turkish War, the Sino-French War, the Sino-Japanese War, the Spanish-American War, the Boxer Rebellion). For this reason some international relations theorists subscribe to what’s called “nuclear peace theory“, the idea that the best way to prevent two countries from going to war is to give them both nuclear weapons. The late Kenneth Waltz was the most noteworthy adherent of this theory.

Opponents of nuclear peace theory argue that states are not sufficiently rational for it to be true. There are two good replies to this. The first is that it does not take much rationality to be deterred by nuclear weapons (a prospective attacker would have to be suicidal to disregard them). The second is that irrationality can cut both ways. On the one hand, irrationality might conceivably cause a state to launch nuclear weapons in a fit of pique. But on the other hand, the possibility that this could happen gives nuclear weapons even more deterrence capability. If there is fear that other states are led by deranged people, other states are far less likely to take any kind of military action that might solicit an overreaction from a deranged government. This suggests that fear of irrational actors could strengthen the deterrence effects of nuclear weapons rather than weaken them.

Another counterargument people often go to is the idea that states will give their nuclear weapons to third parties. This one doesn’t really withstand scrutiny–if a state gives a third party its nuclear weapons, it loses control over where and when those weapons will be deployed. Target countries can also have policies of “expanded deterrence”. This means that if a third party carries out a nuclear attack with weapons it received from some other country, the target country is committed to firing at that other country even though the third party launched the attack. So for instance, if Iran developed nuclear weapons and gave them to a terrorist organization, and that terrorist organization attacked the United States, the US could decide to act on expanded deterrence and deliver a nuclear response against Iran. Even if the chance that the US would do this is not very high, any chance at all is likely large enough to deter Iran from giving nuclear weapons to terrorist organizations.

I don’t think it can be denied that nuclear weapons can provide significant deterrence against foreign adversaries. But this doesn’t necessarily mean that Corbyn is wrong to want to defund Trident. Even without Trident, Britain would be quite safe from foreign adversaries for two reasons:

  1. Nuclear Sharing–Britain is an ally of the United States, which does have nuclear weapons and is committed by treaty to defend Britain from attack. However, Britain can only trust the US nuclear umbrella insofar as it trusts the US to honor its commitments to Britain. One way around this is “nuclear sharing”. Under sharing, the US places missiles in the territory of its allies. This assures those allies that in the event of war, they would be able to deploy these weapons themselves and thereby force the US to honor its treaty obligations. Many NATO member states host American nuclear weapons under sharing agreements, including Belgium, Germany, Italy, the Netherlands, and Turkey.
  2. Paranuclear Capability–many countries do not possess their own nuclear weapons or participate in active nuclear sharing agreements but are still secure because they possess the technology to make nuclear weapons very quickly and easily. These countries could start up a nuclear weapons program today and have a functioning deterrent in as little as a year. Japan, Canada, and Australia are considered to have this paranuclear capability. This strategy banks on a country being able to foresee the risk of an attack 12 months in advance.

If Corbyn entered into a nuclear sharing agreement with the US or retained a paranuclear capability, Britain would be as secure or very nearly as secure as it is with Trident.

Now, some have argued that by claiming that he would never use nuclear weapons, Corbyn has made Britain’s nuclear deterrent useless irrespective of whether he keeps Trident, retains a paranuclear capability, or enters a sharing agreement. The problem with this argument is that even though Corbyn says he would not use the weapons, a prospective attacker cannot be certain that Corbyn will not change his mind. A nuclear deterrent need not rest on the certainty that the defending state would respond by launching nuclear weapons. Even if there is a small chance of nuclear response, this will be sufficient for deterrence because a nuclear response has such overwhelmingly devastating consequences. Consequently, even a very small chance of such a response is intolerable for attackers.

In sum, there are three kinds of nuclear strategies open to a country like Britain:

  1. Independent Deterrent–replace Trident at a cost of £100 billion (about £20 billion up front, with the rest paid over the course of the lifespan of the submarines). This is the sort of strategy France uses. It’s the most expensive and expresses a high level of paranoia about the reliability of the USA.
  2. Nuclear Umbrella with Sharing–scrap Trident and sign a new nuclear sharing deal with the US to station American nuclear weapons in Britain. This is the sort of strategy Germany uses. It’s less expensive and expresses a reasonable level of suspicion about the US’ willingness to go all out in defense of a European ally.
  3. Nuclear Umbrella with Paranuclear Capability–scrap Trident, but maintain the technological and industrial infrastructure necessary to quickly reconstitute the nuclear program within a 12 month period. This is the sort of strategy Japan uses. It’s less expensive and expresses significant trust in the US in the short-term, but it allows the government flexibility if it becomes worried about its ability to deal with a security threat that it anticipates will emerge in a year’s time or more.

Corbyn could emulate the Germans or the Japanese without seriously compromising British security. There are only a handful of states with an independent deterrent (the USA, Russia, France, China, Britain, Pakistan, India, Israel, and North Korea). A few others do sharing, and a few others rely on a paranuclear capability. Most countries still do without any nuclear deterrent at all, and these countries are at a genuinely increased risk of a major foreign intervention by a powerful state on their territory (if Iraq or Libya had a nuclear deterrent, Saddam Hussein and Muammar al-Gaddafi would likely still be in power).

Can you argue that an independent deterrent still gives you a little more security in the short term? Yes. Is this worth £100 billion? I doubt it. We’re talking 3.7% of GDP here. The entirety of the UK’s military forces cost only £45 billion per year, or between 1.5 and 2% of GDP. Even if we only use the median estimate of the up-front costs of Trident (£20 billion), we’re still talking nearly half the conventional budget. It’s worth asking whether it’s worth that kind of money to have France’s security situation rather than Germany’s or Japan’s. Corbyn’s position on nuclear weapons is disputable, but it’s certainly not crazy.