A defense against deterrent nuclear-tipped missiles could also backfire by causing our adversaries to pre-emptively increase the number of missiles in their stockpile. So while the NATO system creates incentives for NATO adversaries and competitors, including Russia and China, to increase their nuclear stockpiles, it offers no credible combat capability to protect the United States or its allies from this -- increased -- weaponry.
And if policy makers mistakenly believe that the strategic missile defense system can protect them from nuclear attack, they may stake out riskier policies than they otherwise would. In fact, it is possible that the protection afforded by Iron Dome may have played a role in encouraging Israel to escalate the recent conflict, secure in the system's effectiveness. A similar escalation, but with a dysfunctional missile defense system, may lead to a much more dire nuclear miscalculation.
But what if a system could be invented that did offer a high degree of protection from long-range nuclear missiles? Unfortunately, such a system would only encourage a change in the delivery method of the nuclear weapons used by our adversaries. It would not devalue the nuclear weapons themselves.
A "functional" missile defense to counter North Korea's ICBMs, for example, could encourage Pyongyang to develop a ship-borne nuclear device instead. Since such a weapon is more difficult to detect and attribute to a given country, our adversaries may be less inhibited in using it as compared to an easily detected ICBM, which has a clear point of origin. (U.S. satellites continually monitor the globe for missile launches.) So if a missile defense encouraged our adversaries to exchange even a single ICBM for a ship-borne one, our security would actually decrease. Of course, an adversary might develop these alternate delivery methods in any case, but creating incentives for them to do so is not in our interest.
In short, if our adversaries obtain nuclear weapons, we should actually hope that they are mounted on missiles, because missiles are attributable -- we can pinpoint their launch sites -- and thus our enemies are deterred from using them. The real danger of a strategic missile defense that works is that it may work to discourage the missiles -- without discouraging the nuclear weapons themselves.
The real lesson in all this is that we should work hard to stop the spread of nuclear weapons -- once our adversary has them, we will be deterred no matter what kinds of defenses we think we have. But to stop the spread of nuclear weapons we need the assistance of major players like Russia and China. Ironically, the infatuation with the NATO missile defense ensures that we don't get that cooperation because those nations may fear that the system alters the strategic balance with the United States. Indeed, the bipartisan Strategic Posture Commission has pointed out that "China may already be increasing the size of its ICBM force in response to its assessment of the U.S. missile defense program."
Although Iron Dome has been remarkably successful in intercepting slow-moving battlefield rockets in the atmosphere, one ought not jump to conclusions about what this means about attempting to defend against high-speed nuclear missiles in space -- or even its desirability.