The Pentagon's own Defense Science Board report on NATO missile defense says that "the importance of achieving reliable . . . discrimination [between the warhead and decoys] cannot be overemphasized." It underlined that missile defense is "predicated on the ability to discriminate" real warheads from other targets, "such as rocket bodies, miscellaneous hardware, and intentional countermeasures." And if "the defense should find itself in a situation where it is shooting at missile junk or decoys, the impact on the regional interceptor inventory would be dramatic and devastating!" In short, the interceptor inventory would be exhausted in chasing decoy warheads, rendering the system useless.
Both because they are about ten times slower than long-range missiles and because they fly through the atmosphere, the Hamas rockets are much easier to intercept. Any decoys would quickly slow down in the atmosphere and be rendered ineffective and so none are used. So extrapolating the success of Iron Dome to the NATO system is technically unwarranted -- they are entirely different beasts.
Another big difference between Iron Dome and the NATO missile defense system is the nature of the threat. Iron Dome guards against small battlefield rockets that are actually used, whereas the NATO missile defense system is designed to counter nuclear-tipped missiles that are useful for their deterrent value and that have never actually been used since they were invented. Such missiles are intended to protect one's own nation and influence adversaries' strategic calculations; they are not fired off in everyday battles.
So an 80 percent-effective tactical missile defense system against conventional battlefield rockets -- such as Iron Dome -- makes a lot of sense. If 10 conventional rockets are headed your way, stopping eight is undeniably a good thing. The possibility of stopping eight of 10 nuclear warheads, however, is less decisive in altering strategic calculations since even one nuclear explosion will inflict unacceptable devastation. Just one nuclear-tipped missile penetrating your missile shield is about the equivalent of a million conventional missiles making it through. An imperfect -- or, as is the case in the NATO incarnation, a deeply flawed -- missile defense system doesn't alter the deterrent calculus between states. At least, it shouldn't.
So even after NATO has set up and activated a strategic missile-defense system, it still will not have neutralized the perceived threat from Iran -- if and when Tehran obtains nuclear weapons -- or North Korea. Not only that, but Washington's strategic calculations toward our adversaries will remain unaffected: The United States will still need to be just as worried about Iran's missiles, since the destruction of even one NATO city or region is simply too high a cost to bear. For that security calculus to change, national missile defense would need to intercept 100 percent of incoming nuclear warheads. This is an unattainable goal for any piece of machinery, and especially for the system being fielded, given the government's own damning scientific assessments.
As Pavel Podvig succinctly put it, "it would take only a small probability of success to make such a [nuclear] threat credible while missile defense would need to offer absolute certainty of protection to truly be effective." Even the largely successful Iron Dome system, while providing a worthy cover has not provided normalcy for Israeli citizens: the terror is still there.