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Since the beginning of warfare, humans have sought defenses against offensive weapons. Not surprisingly, then, the deployment of nuclear-armed missiles by the United States and the Soviet Union early in the Cold War prompted each to begin building missile defenses to protect themselves against these extremely destructive weapons.

What is perhaps surprising is that both countries soon recognized that this undertaking would be destabilizing and pointless and agreed in the 1972 Anti-Ballistic Missile (ABM) Treaty not to defend their countries against each other’s ballistic missiles. The two superpowers both based their nuclear policies on the notion of deterrence-that maintaining the ability to launch a nuclear counterattack that would inflict massive destruction on the other side was necessary to ensure that the other country would not attack first.

Missile defense could weaken or even negate the retaliatory capability of the other side, since a retaliatory attack would be small and uncoordinated. Thus, it was believed, their deployment would provoke the other country to take measures to preserve its deterrent. One straightforward but dangerous response to a defensive system would be to build up the size of the offensive arsenal. Another would be to adopt a policy of “launch on warning,” which would permit missiles to be launched rapidly when sensors detected an incoming attack. This policy would prevent a country from being disarmed by a first strike but would increase the risk of accidental launch since the decision to launch would need to be made quickly.

Both responses would lead to a more dangerous world, while making the quest for effective defenses futile. It was to avoid this destabilizing dynamic that the United States and the Soviet Union signed the ABM Treaty.

In the mid-1980s, President Reagan, rejecting the logic of the ABM Treaty, launched the Strategic Defense Initiative. Under this program, often referred to as “Star Wars,” the Pentagon focused on advanced technologies such as space-based lasers to develop a multi-layered defense of the United States against a large-scale Soviet attack. The nation spent tens of billions of dollars on R&D. The program eventually lost political support, however, because opponents successfully argued that any advances in technology were irrelevant-that Soviet responses would still prevent defenses from being effective-and that building them would diminish, rather than enhance, U.S. security. The logic of the ABM Treaty ultimately prevailed.

But the United States is again moving toward deploying defenses against attacks by ballistic missiles. Iraq’s use of conventionally armed Scud missiles against Israel and Saudi Arabia in the 1991 Gulf War raised concern about the proliferation of ballistic missiles, and U.S. efforts shifted away from a system that would shield the entire country from large-scale Soviet attack toward “theater” defenses, designed to protect U.S. troops and allies abroad from shorter-range missiles. But after taking control of Congress in the 1994 election, Republicans put deployment of “national” defenses-this time intended to counter limited missile attacks against U.S. territory-back on the agenda as well.

Proponents of the new missile defense systems argue that the risks to national security of building defenses are lower than in the past, and the benefits higher. Most fundamentally, some argue, the United States and Russia are no longer enemies; Moscow would not be threatened by U.S. missile defenses and thus would not respond in ways that would hurt U.S. security. Other proponents argue that even if U.S. missile defenses did worry Russia, that economically strapped country could not afford an arms buildup in response.

Still other proponents note that today’s missile threats are different: their concern is no longer a deliberate large-scale Soviet nuclear attack but rather an accidental or unauthorized launch of missiles by Russia, an attack by China, or possibly threats from Third World countries that acquire long-range missiles. Guarding against these attacks, they argue, would require only limited national defenses that would not threaten Russia’s much larger nuclear deterrent. Moreover, this argument continues, U.S. deployment of theater defenses should not concern Russia since these systems would not be intended for use against Russian missiles.

Missile-defense advocates argue that the benefits of deployment are higher than during the Cold War because there is a real and increasing missile threat that it is possible to defend against. They argue that missile-defense systems are far more likely to work against the shorter-range missiles, and against attacks from a small number of long-range missiles, than against a massive assault by sophisticated, long-range missiles-the threat that motivated previous missile-defense programs.

Both political parties have, to varying degrees, bought into the idea that missile defense of some kind is a practical and wise idea; the United States has for the past few years been spending roughly $3 billion a year to study and develop such systems. While this total is down from the peak of some $4.5 billion a year at the height of the Strategic Defense Initiative in the late 1980s, it is far from clear that even this level of effort makes much sense. Thus far, this money has bought only research, development, and testing; building, deploying, and maintaining the systems would require much larger budgets.

Despite the breakup of the Soviet Union, things have not changed quite so much as missile-defense advocates suggest. Proponents overstate the missile threat and the ability of defenses to address what threat exists. Perhaps most importantly, they largely ignore the potential security costs of deploying many of the defenses being developed.


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