Chinese concerns about U.S. missile-defense systems are also a source of great uncertainty, reducing Chinese support for promoting negotiations on the Fissile Material Cutoff Treaty (FMCT)—China's leaders may wish to maintain the option of future military plutonium production. The bipartisan Strategic Posture Commission points 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.”
But if Tehran obtains nuclear weapons, surrounding it with missile defenses, no matter how effective, will never eliminate the threat that a single missile could penetrate the defense system—especially given how easy it is to outfox the system by using decoys. Thus, the United States can never neutralize the deterrent value of any possible future Iranian nuclear ballistic missiles with any incarnation of missile defense. A nuclear-armed Iran would have to be treated identically by Washington whether or not missile defenses were in play.
The strategic uselessness of missile defenses aimed at devaluing nuclear-tipped missiles is a conceptual problem, not merely a technical one. The reason is simple: there is always a reasonable probability that one or more nuclear missiles will penetrate even the best missile-defense system. Since even a single nuclear-missile hit would cause unacceptable damage to the United States, a missile-defense system shouldn't change U.S. strategic calculations with respect to its enemies. Washington would treat North Korea, Iran and other adversaries the same before and after setting up a missile-defense system.
It's often asserted that missile defenses dissuade adversaries from researching and producing ballistic missiles. But the countries developing ballistic-missile technology do so for numerous reasons, not just to launch nuclear attacks against the United States. Many countries desire conventional ballistic-missile technology for prestige or regional security. Whether or not a U.S. missile-defense system is operational, such nations will still try to acquire ballistic-missile technology. In fact, the countries of most interest to the United States—Iran and North Korea—currently have reasonably well-developed ballistic-missile programs. They have not been dissuaded by the missile-defense “shield.”
And even if some future incarnation of missile defense could be made to work effectively, it 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, may encourage the nation to develop a ship-launched nuclear cruise missile instead or to deliver nuclear weapons directly by boat. Since a cruise missile or boat-borne nuclear device is more difficult to detect and attribute to a given country, our adversaries may be less inhibited in using such delivery methods as compared to an easily detected ICBM with a clear point of origin.
Missile defense will not counteract any possible future Iranian ICBMs with simple countermeasures—but it will erode relations with Russia and China right now. Because it encourages adversaries to assume the worst and creates incentives for them to increase their nuclear stockpiles, it will also lead to more nuclear weapons and a more dangerous world. There is simply no upside to a dysfunctional missile “defense” and plenty of downsides in addition to its gargantuan cost.
Yousaf Butt is a nuclear physicist and serves as a scientific consultant to the Federation of American Scientists, a DC think tank.