So far, tests have seemed promising but inconclusive. A test firing did work last year, but in January, a defensive missile missed a dummy warhead. Another test is planned for June. These tests, however, don't account for wily weapons alterations. Even if it works, a National Missile Defense defends against only one way of wreaking mass destruction.
Defense depends on rigorous intelligence-gathering and law enforcement.
The decision on this new system also must consider the overall goal of arms reduction and the particular requirements of arms treaties. The 1972 Antiballistic Missile Treaty prohibited national anti-missile systems. Russia, echoed by U.N. Secretary-General Kofi Annan, has warned the United States not to break that agreement. But giving each other permission to rush to build an expensive National Missile Defense makes no sense. Thus the nervous rush for an antimissile defense against Iran or North Korea is overwrought.