The Bush Administration’s urge to national missile defense has sparked yet another visitation of debate over the 1972 ABM Treaty. This is depressing news, for ABM Treaty debate reminds one of Brigadoon. Like the fabled village of a rancidly sentimental musical, this debate comes and goes with annoying regularity— and the mindless lyrics never change. This time around, however, the debate may come finally to a helpful conclusion. To do that, however, some insufficiently appreciated truths about the treaty need wider propagation.

This need is indicated by a widespread reaction to the President’s May 1st speech, which has been to decry the “squandering” of a treaty that has been the “cornerstone of strategic stability” for thirty years. But the mere endless repetition of this mantra does not make it correct. The Bush Administration is right about the ABM Treaty; if anything, its rhetoric is too mild. The treaty is not just passe. Rather, it has been an obstacle to strategic stability, not a cornerstone of it.

Since mantras are by definition severed from their foundation logic, let us restate the theory from which this particular one has derived. Its core premise is that assured destruction capabilities are stabilizing and that defenses, since they undermine assured destruction, are bad. The theory asserts further that in the absence of defenses the actors will lose their appetite for further offensive proliferation once they have acquired sufficient means for deterrence. Strategic arsenals will then come to rest on a more or less stable plateau. Building defenses, however, will generate uncertainty leading to further offensive proliferation as a hedge. If both build defenses, then both will proliferate offenses, and the result will be an open-ended arms race. That’s bad, too, sayeth the theory (even though in some cases arms competitions can be stabilizing rather than destabilizing).

As theories go, this one seems logical enough. But if the theory were correct, then the ABM Treaty should have produced a leveling off of offensive proliferation. It didn’t. The years following the ABM Treaty witnessed the largest and most rapid expansion of offensive strategic nuclear proliferation in history by nearly every measure one can bring to the subject. Why did this happen?

It happened both because of the reigning psychological dynamic of the Cold War and because a key technological shift turned the logic of defense within the assured destruction paradigm on its head. Around 1974 intercontinental ballistic missiles started to become accurate enough to attack other missiles— a phenomenon called counterforce. Instead of guaranteeing a free ride for missiles aimed at destroying cities, the absence of defense guaranteed a free ride for missiles aimed at negating an adversary’s assured destruction capabilities— that is, at its second-strike missile force.

The advent of counterforce capabilities made it possible that a significant offensive advantage could be used to mount a disabling and disarming first strike. Planners could imagine a numerically superior force eliminating the threat of retaliation by combining the preemptive destruction of most of the other side’s forces with the continued hostage-holding of its population. Counterforce thus created a situation conducive not to reaching a plateau among strategic arsenals, but to proliferating offenses to achieve such an advantage.

The ABM Treaty magnified the problem. In a counterforce world, area defenses may be destabilizing because they might appear to be part of an offensive-minded first-strike strategy. In such a strategy, area defenses would soak up— or deter altogether— a rag-tag second strike, so it makes theoretical sense, at least, to ban or limit them. But one cannot argue that point defenses (defenses that make missiles more survivable) are destabilizing. To the contrary; protecting second-strike retaliatory forces at risk from counterforce attack makes utterly good sense. Yet the ABM Treaty banned significant point defense, limiting it to a single missile field. The treaty thus made offensive proliferation especially attractive to counterforce-minded Soviet planners.

And indeed, the Soviets furiously proliferated new counterforce-capable systems in the decade after 1972. The United States responded in part by seeking the elusive plateau of stability through arms control, but failed to create it. The SALT II effort of 1975-79 proved futile because the Soviets negotiated to preserve their own building programs while locking in constraints on U.S. defenses. In the end, the United States felt compelled to build more missiles to compensate for Soviet efforts, and to search for ways to make those missiles survivable in the absence of point defense (e.g., “dense pack,” rail-mobile missiles, and other such pained and strained deployment schemes).

Clearly, then, the ABM Treaty did not help constrain offensive proliferation, but was a major stimulus of it. The historical facts notwithstanding, many still believe that the absence of all defense in a counterforce world limits offensive proliferation, and a wonder to behold it is. The belief that the ABM Treaty has effectively limited offensive proliferation, despite the compelling empirical evidence to the contrary, is even less logical than the belief that garlic necklaces keep away elephants … where the evidence is necessarily counterfactual.

While the urge to proliferate can be influenced by technological change, it is predicated mainly on political realities. U.S.-Russian offensive proliferation has virtually ceased in recent years mainly because the Cold War is over— not because the Russians are broke, not because of a dearth of technical improvements relevant to strategic weapons development, and certainly not because the ABM Treaty exists.

But what of new political realities? The United States does need to protect itself against missile attack. President Bush’s stated rationale notwithstanding, however, basket-case extortionist regimes such as North Korea are not the biggest future threat. Such threats can and should be managed through far more modest theater missile defense efforts combined with supple diplomacy. The case for national missile defense instead rests on the generic problem of “inverted deterrence” that the United States faces in the years ahead.

It is likely that many medium (and larger) powers over the next few decades will attain deliverable weapons of mass destruction. Without defenses against them, the very possession of such capabilities will narrow U.S. military expeditionary options and raise their prospective costs. It will also discount the efficacy of American forces stationed or sailing abroad, forces whose major contribution to international security is neither to compel nor to deter others, but to reassure them. The broad efficacy of U.S. diplomacy will suffer in consequence; the United States cannot lead in the maintenance of the global security commons— it cannot conduct a supply-side diplomacy, as Josef Joffe likes to call it— if multiple forces de frappe preemptively shackle the exercise of U.S. power. This, in a nutshell, is the problem of inverted deterrence.

Unfortunately, many of our allies seem unable to grasp what is at stake despite the fact that, by dint of geographic realities, their lands and people will be vulnerable before those of North America to new missile forces. Moreover, new limits on the flexibility and credibility of U.S. expeditionary forces will undermine their security before it affects ours, in two ways. First, it will make U.S. conventional forces less imposing as an instrument of extended deterrence and, in consequence, it will raise the political profile of nuclear weapons.

Obvious as this is, it is nevertheless unwise to dragoon our European allies, in particular, into tepid support for U.S. missile defense when other serious Atlantic security issues remain unresolved. How to bring them around? Real consultations are critical and, to its credit, the administration understands this. U.S. envoys now taking to the road might start by telling them the truth about the ABM Treaty.