Strategic stability is one of those ideas that seem to enjoy almost unqualified support among nuclear and non-nuclear weapon states, nuclear disarmament advocates and skeptics, as well as nuclear abolitionists and nuclear hawks. And it is probably because of this universal support that the pursuit of strategic stability became the single most serious obstacle on the way toward nuclear disarmament.
Strategic stability usually refers to a state of affairs in which countries are confident that their adversaries would not be able to undermine their nuclear deterrent capability. It is generally believed that, if the nuclear deterrence potentials are secure, nuclear powers would not feel the need to build up their strategic arsenals and, most important, would not be under pressure to launch their missiles in a crisis. Understood this way, strategic stability does not seem a particularly controversial concept. Few people would advocate instability in matters that involve nuclear weapons. But the problem is that the key elements of the concept are so poorly defined that it has no useful meaning and virtually no practical value.
First of all, the numbers that are used to judge the effectiveness of deterrence have always been completely arbitrary. For example, in the early 1980s, the US intelligence agencies estimated that, in the event of a surprise Soviet attack, surviving launchers in each of the three legs of the US strategic triad could independently destroy about 70 percent of the Soviet economic value -- a task that would require thousands of surviving warheads. And still the United States was concerned that this might not be enough to deter the Soviet Union. The Soviet Union, on the other hand, had a different view of what was necessary for effective deterrence: A Soviet official document from the late 1980s estimated that its retaliatory strike would destroy about 80 targets on US territory. Given that the Soviet strategic force still included more than 10,000 nuclear warheads at the time, this number does not seem particularly large. However, the authors of the estimate seemed quite confident that such a capability would provide the Soviet Union with an adequate deterrence potential.
These numbers are probably much lower today, but they are almost certainly as arbitrary as they were in the 1980s. All evidence suggests that the estimations of the number of weapons that might be required for deterrence have always been determined by the number of weapons available -- rather than the other way around. So, once nuclear states start cutting down their nuclear arsenals, they have no problem adjusting their views of efficient deterrence accordingly. In August, for example, a former commander of the US Strategic Command stated on record that "the retaliatory capability of 300 nuclear weapons on anybody's territory is catastrophic." But there is no reason to believe that the retaliatory capability of, say, 30 nuclear weapons -- or even three -- is anything but catastrophic. Indeed, the experience of the Cuban Missile Crisis or concerns about the emerging nuclear capabilities of countries like North Korea and Iran tells us that just a small probability of having a single nuclear weapon delivered to someone's territory is a very strong deterrent.
The arbitrary nature of the assumptions that underlie the idea of strategic stability makes this concept extremely malleable and politically charged. Depending on the politics of the moment, just about any configuration of strategic forces could be declared sufficiently stable or dangerously unbalanced, and any imaginable threat could be brought into the equation or conveniently ignored. On the surface it may not look this way -- there is, after all, an intellectual tradition that explains, for example, why silo-based multiple-warhead missiles are destabilizing weapons or why missile defense undermines strategic stability. Historically, however, it has always been the politics and not the theoretical arguments that have had the upper hand in most of these discussions; even the most difficult strategic stability problems are usually resolved by a simple decision that they are not problems anymore.
Somewhat surprisingly, one of the best examples of the triumph of politics over theory is the Anti-Ballistic Missile Treaty (ABM), which has long been believed to embody the essence of strategic stability calculations by limiting destabilizing missile defenses and introducing a measure of predictability into the nuclear arms race. In reality, however, the decision to limit defenses came only after the United States and the Soviet Union had enough experience with missile defense to conclude that it would not be able to provide any useful protection. By the time the ABM negotiations began, neither country believed missile defense was going to be a serious problem.
During the MX missile debate in the late 1970s -- in which the United States built its most advanced intercontinental ballistic missile to date -- there was a great deal of controversy over the seemingly insurmountable problem of multiple-warhead land-based missile vulnerability. For a time, the missiles were supposed to be shuttled around the United States in an intricate, expensive, and wildly uncertain ploy to make them less vulnerable to Soviet attack. And yet, the matter was quickly resolved once the large-scale strategic modernization of US forces got underway in the early 1980s -- the missile vulnerability controversy had served its political purpose and the missiles were deployed in silos, even though they were as vulnerable as before.
Another example is Russia's recent position on missile defense, which -- despite all the harsh rhetoric -- turns out to be surprisingly flexible. The alleged grave destabilizing effects of missile defenses were conveniently overlooked every time the political benefits of moment felt right -- whether it was the Strategic Arms Reduction Treaty (START) in 1991; the brief US-Russian rapprochement after the 9/11 attacks, which the United States used to withdraw from the ABM Treaty; or the success of New START in 2010.
Missile defense, of course, is back on the agenda, but only because the politics changed: Having secured an arms control agreement with the United States, Russia now needs a cover for its strategic modernization program. Besides, missile defense is far from the only problem that is being added to the strategic stability mix; there are weapons in space, conventional strategic weapons, upload potential, cruise missiles, and the balance of conventional forces.
Though as tempting as it might be to try to find a formula that would balance all these factors in one neat, strategically stable package, it is never that simple. The only reliable way to deal with the many alleged threats to strategic stability is to build a system of relationships in which countries make conscious decisions to exclude these "threats" from their national security calculations. This approach is, of course, a rather tall order; it would probably require a fundamental change to the architecture of international security, as well as to US policy and to the policies of other nuclear weapon states. But, unless the international community commits itself to a more rational security regime, the world could get bogged down in a quest for strategic stability -- which is increasingly becoming nothing more than a cover for obstructionism and cynicism in nuclear disarmament.