On Nuclear Weapons, You Can Never Say Never | Eryn MacDonald

There’s been an unusual debate going on over the past couple of weeks in the United Kingdom after Jeremy Corbyn—head of the Labour party—declared that if he were to become Prime Minister, he would not use nuclear weapons. Not everyone was happy with his statement, but it also seems not everyone understands how nuclear deterrence works.

Britain and the Bomb

The U.K. is one of the five nuclear weapons states acknowledged in the Nuclear Nonproliferation Treaty. It relies on an arsenal made up entirely of warheads deployed on Trident submarine-launched ballistic missiles. Following recent reductions, four submarines carry no more than eight missiles each, each armed with no more than four warheads, with no more than 120 weapons deployed at one time. This means the United Kingdom has the smallest arsenal of the five nuclear weapons states. But even with those reductions, the country is not uniformly enthusiastic about its nuclear-armed status. Opinion polls have shown that the public is divided over the value of the Trident program, and the decision on whether to replace it is looming. Moreover, last year, during a referendum on Scottish independence, the Scottish National Party promised that an independent Scotland would be nuclear-free within four years. Since the submarines carrying the U.K.’s Trident missiles are based in Scotland, this would have left the U.K. with no workable base for their nuclear submarines. The referendum failed, but the debate over the future of Trident has not faded away.

For his part, Corbyn is an inveterate opponent of nuclear weapons and advocate of nuclear disarmament, so his position on this issue should not come as a big surprise. But the fact that the potential national leader of a nuclear weapon state would publicly declare his refusal to use such weapons has brought up interesting questions about how deterrence works and what it requires to be effective. In the hype surrounding Corbyn’s statement, it has become clear that there are some very basic misunderstandings about how deterrence works.

The Only Certainty Is that Nothing Is Certain

The biggest misunderstanding is the idea that some have expressed that Corbyn’s statement would undermine Britain’s deterrent altogether if he became Prime Minister. This is apparently based on the theory that because Corbyn has clearly stated that he is unwilling to use nuclear weapons, adversaries would be convinced that no matter what they did—presumably even attack the U.K. with nuclear weapons—they would not have to fear a nuclear strike or nuclear retaliation.

The problem here is that deterrence is often based not on certainty but uncertainty: uncertainty about capabilities, or intentions, or both. If capabilities are known not to be present, there is no question—no deterrence is possible. If capabilities may be present, then that uncertainty can be enough to provide deterrence.

But if capabilities are known to be present, then, despite all the assertions of policy and principle in the world, one can never be sure about intentions—some uncertainty will always remain, meaning that deterrence will still be in effect.

The main point is that, for deterrence, certainty is not required. Deterrence continues even if, in Thomas Schelling’s words, it is based on a “threat that leaves something to chance.”

President Nixon’s “madman strategy” took this idea further. Nixon attempted to convince adversaries that he was crazy enough to do anything, including starting a nuclear war, in order to get his way. A prime example of this strategy in action was Nixon’s effort in 1969 to end the Vietnam war on favorable terms by secretly ordering the U.S. military to full readiness alert for global war. This alert level included sending U.S. bombers armed with nuclear weapons to fly patterns near the Soviet border. The alert was designed to be detected by the Soviet Union and North Vietnam, but be unknown to the American public. Nixon explained that “I want the North Vietnamese to believe I’ve reached the point where I might do anything to stop the war. We’ll just slip the word to them that, ‘for God’s sake, you know Nixon is obsessed about communism. We can’t restrain him when he’s angry—and he has his hand on the nuclear button’….”

Nixon’s calculated strategy of acting unpredictably follows from the importance of intentions and credibility in deterrence theory. If it is not credible that a sane person would start a nuclear war, then maybe the best thing to do is to act slightly insane. But the performance has to be credible, hence Nixon’s need to order forces to heightened alert levels as evidence of his insanity, despite the increased risk of accidents or misunderstandings that this created.

In Deterrence (Reassuring) Talk is Cheap

Returning to the current British situation, the question is not whether a leader can make a credible commitment to use nuclear weapons in a given situation, but whether an adversary would ever be confident in Corbyn’s pledge never to use nuclear weapons.

Note that the United States routinely discounts China’s longstanding declaration of a no-first-use policy for nuclear weapons as empty rhetoric. This is true even though China has always maintained a much smaller arsenal than the United States or Russia and has not shown a desire to greatly increase it. China also backs up its declaration by storing its warheads separately from its missiles, so that a period of time would be required to prepare them for launch, unlike the United States and Russia, which keep their missiles on hair-trigger alert, ready to launch at any moment.

As this example shows, even a clear and consistent policy declaration maintained over decades, combined with a force structure that corroborates this policy is not enough to convince potential adversaries that China’s no-first-use commitment is credible.

The bottom line is that as long as nuclear weapons exist, adversaries must consider the possibility that they will be used, thus the uncertainty required for deterrence remains in effect. And Jeremy Corbyn, however sincere he might be in his beliefs, cannot change that.

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