Today marks the tenth anniversary of the unilateral U.S. withdrawal from the Anti-Ballistic Missile (ABM) Treaty. The treaty, in force for 30 years, limited the number and type of missile defenses the United States and the Soviet Union (and afterwards Russia) could deploy against strategic offensive missiles.
Announcing the withdrawal in the wake of the terrorist acts of September 2001, President George W. Bush declared Russia was no longer an enemy and that the principal security threats to the United States and Russia were now “weapons of mass destruction and their delivery means wielded by terrorists and rogue states.” He argued that limited missile defenses are key to deterring and protecting against these threats, and that the ABM Treaty hamstrung U.S. development efforts.
Has removing the limits of the ABM Treaty led to the development of effective defenses? No, it hasn’t.
After ten years with no legal restraints (and few financial restraints), the United States still does not have a missile defense system able to reliably defend against even a limited long-range missile attack. Although 30 interceptors have been fielded as part of the Ground-Based Midcourse missile defense (GMD) system, and the first of four phases of the Obama administration’s Aegis ship-based Phased Adaptive Approach has been completed, the United States has little ability to defend against a missile attack.
The failure to provide an effective defense against a real-world attack is primarily due to a fundamental problem with these systems: they can be fooled by decoys and other countermeasures. These defenses are designed to intercept missiles during the “midcourse” of their flight when they are above the atmosphere. Since warheads and lightweight decoys follow the same trajectories in the vacuum of space, the attacker can take steps to deny the missile defense sensors the information the defender needs to distinguish the warhead from large numbers of decoys. The defense would have to try to intercept all the objects it sees—decoys and warhead—but would not have enough interceptors to do so. The recently completed study by the National Academies of Science concurs that “There is no effective ballistic missile area defense that does not require dealing with midcourse discrimination.”
In its 1999 assessment of missile threats, the U.S. intelligence community noted a list of readily available technologies and stated that countries developing long-range missiles “could develop countermeasures based on these technologies by the time they flight test their missiles.” It makes no sense to assume that a country developing missiles would not equip them with decoys or other countermeasures to make them effective. This fundamental technical problem of missile defense has been known for decades, but has not been solved despite efforts to build more sophisticated sensors.
The testing programs of these defenses in no way indicate that the systems would be effective against real attacks. Since the June 2002 withdrawal from the ABM Treaty, the United States has conducted only nine intercept tests of the GMD system, and only four of these—fewer than half—were successful. The Aegis system has had more tests and a higher success rate in those tests, but all of those tests have been under scripted conditions without realistic countermeasures and therefore say essentially nothing about how the system would perform against a real attack. The Government Accountability Office stated this in its February 2008 report, concluding that the GMD tests have been “developmental in nature, and do not provide sufficient realism” to assess the system’s potential effectiveness.
Not only do these missile defenses not provide effective defense, they are counterproductive. U.S. missile defense plans currently are a major irritant in U.S.-Russian relations. While Russian and Chinese countermeasures could fool U.S. missile defenses, conservative military planners in those countries would likely recommend still keeping larger number of missiles in response to defense deployments than they otherwise would. So deployment of missile defenses is likely to be a barrier to steps toward deep reductions in nuclear weapons and their delivery systems. This makes the U.S. less safe, not more.
That was the logic behind the ABM Treaty when it was negotiated 30 years ago: limits on missile defenses are important to limiting offensive missiles. That logic still applies. Withdrawing from the treaty has led to the United States buying expensive hardware but has not led to effective defenses.
There is little prospect that the United States will develop a system that could defend against real-world long-range missiles in the foreseeable future. If U.S. attempts to gain security this way block steps that could truly increase security by reducing nuclear arsenals, that is the worst of both worlds.