The U.S. Missile Defense Agency acknowledges that the proposed system could not handle an attack of that kind. The military recognizes that the first interceptor might miss its target and therefore plans to shoot as many as five interceptors at each incoming missile, in order to reduce the probability that the defenses might be penetrated. The idea is that if the first interceptor misses, the second might not, and so on. If Iran were to attack Europe with two missiles, and the defense were to fire five interceptors at each one, the ten interceptors that are planned for deployment in Poland would be quickly used up. If Iran were to launch more than two missiles at Europe, there might be no interceptors left to repel further attacks.
If Iran believed that U.S. missile defenses were effective and was reckless enough to want to attack Europe or the United States, it could simply build more missiles to overwhelm those defenses. If Iran were to attack Europe with more than one or two missiles, the European missile defense system as proposed could not defend Europe.