The terrorist attacks on New York and Washington on September 11, 2001, were both good and bad news for the Bush Administration's early commitment to the near-term deployment of defenses against ballistic missiles. The good news was that the vulnerability of the American homeland to devastating attack was demonstrated to be real, not merely a figment of the overactive imagination of Reagan-era strategists. The bad news, on the other hand, was that the method of attack utilized by the terrorists involved neither ballistic missiles nor nuclear weapons. Al-Qaeda's largely unanticipated concept--the use of fuel-laden commercial airliners in suicide missions to produce enhanced conventional explosive effects--inflicted less damage than might be anticipated from most so-called weapons of mass destruction, but it was well suited to a technically constrained and low-budget terrorist organization.

Critics of ballistic missile defense (BMD) were quick to seize on 9/11 as proof that the real threats of the future were likely to come not from intercontinental-range missiles with a recognizable "return address", but rather from a variety of possible weapons or devices clandestinely inserted into the United States, or even from aircraft or cruise missiles originating within the country or not far from its borders. They argued that states capable of attacking the United States with long-range ballistic missiles will continue to be deterred from such a step by America's overwhelming retaliatory capabilities. And missile defense is technically problematic and enormously expensive compared to other pressing defense needs.

But the debate over missile defense, nuclear strategy, and arms control ignited some twenty years ago by Ronald Reagan's Strategic Defense Initiative (SID) and sustained since then in well-worn paths is now winding down. The president's announced commitment at the end of last year to deployment of a limited BMD capability beginning in 2004 has made clear to all concerned that BMD in some form is shortly to become a reality. And yet bad habits contracted in the course of that debate continue to color much commentary on this subject. Perhaps the fundamental point is that missile defense must not be narrowly viewed in technical or purely military terms. The various technical problems and limitations of the BMD systems that the United States has had under development over the last two decades have figured prominently in the critics' case. While these challenges should not be underestimated, one would be foolish to bet against American technological ingenuity in the military realm, so spectacularly demonstrated in our recent demolition of Saddam Hussein's armed forces and regime; this is even more true now that the political constraints that hobbled BMD development in past years have been removed by American withdrawal from the Anti-Ballistic Missile (ABM) Treaty of 1972. Nor can the issue be reduced to a calculus of exchange ratios of the kind that so often dominated analyses of hypothetical nuclear conflict in the Cold War, though there are certainly abundant operational and tactical issues concerning BMD that remain to be addressed. Rather, missile defense needs to be analyzed as a strategic capability that is part of the larger tool kit of American power, one with an important psychological and political dimension that can generate benefits but also holds potential risks. Above all, missile defense must be considered not merely in relation to adversaries but as an instrument for reinvigorating existing alliances and forging new ones--indeed, as a central component of the "new world order" that is now being shaped by American global activism in the war on terror.

Getting Serious

In December 2001 the Bush Administration took a long-anticipated step away from the Cold War nuclear arms control regime by providing notice to Russia that the United States intended to withdraw from the venerable ABM Treaty. Critics of the Administration's commitment to BMD had predicted it would cause a diplomatic uproar, but Russian reactions were surprisingly muted, and previously vociferous European critics were as a result largely silenced. Indeed, the Russians began to talk increasingly of developing or enhancing their own defenses against rogue-state missiles, perhaps in cooperation with the Europeans or with the United States itself. Immediately following the treaty's expiration, the United States began aggressive testing of missile defense radars and interceptors in ways that would not have been permitted under the treaty regime. By the end of the year, enough progress had been made in various BMD technologies that the president felt confident in taking the next step, formal commitment to the deployment of a rudimentary BMD capability beginning in 2004.

In a statement released by the White House on December 17, 2002, the president emphasized the importance of missile defenses in the new strategic environment, where hostile states or terrorist groups not subject to the traditional calculus of deterrence can threaten the United States with catastrophic destruction. He also made clear that the commitment to develop viable BMD systems was not a narrow commitment to the integrity of the American homeland, but extended as well to American military forces deployed abroad and--not least--to the nation's friends and allies, and he declared obsolete the distinction between "national" and "theater" defense systems that the United States had previously observed in the context of the ABM treaty. He also called on other nations to join the United States in a common effort to develop advanced technologies for missile defense.

The detailed plan released by the Pentagon in conjunction with the president's statement distinguished initial capabilities from additional measures to be taken by the end of this decade. Initial capabilities were said to include up to twenty ground-based interceptors designed to destroy intercontinental ballistic missiles (ICBMs) in the mid-course phase of flight, with 16 of them to be based in Fort Greely, Alaska, and four at Vandenberg Air Force Base in California; up to twenty interceptor missiles based on U.S. Navy Aegis cruisers and destroyers with a capability to counter ballistic missiles in the boost or ascent phase; air-transportable pac-3 (advanced Patriot) systems geared to counter shorter-range ballistic missiles in the terminal phase of their flight; and upgrades to various sensors, including early warning radars located in the United Kingdom and Greenland. Additional measures to be pursued after 2005 were said to include additional ground- and sea-based interceptors; the Theater High Altitude Area Defense (THAAD) interceptor geared to shorter-range missiles; the Airborne Laser, a Boeing 747 equipped with a high-energy chemical laser capable of destroying missiles in their boost phase from hundreds of miles away (seven of these aircraft are slated for eventual procurement); enhanced radars and other sensor capabilities; and the development and testing of space-based defenses, including kinetic-energy interceptors. This program built on the BMD development effort of the Clinton years, but went beyond it in several ways, notably in its new emphasis on sea- and space-based systems, previously proscribed by the ABM Treaty.

Defense Department officials have emphasized that it is too early to predict the exact mix of capabilities to be deployed after 2005, but the intent is to create a multi-layered missile defense system capable of providing protection against the full range of potential "limited" ballistic missile attacks, whether on the homeland or on American forces or allies abroad. In this respect, the president's program differs dramatically from the original SID concept, which was directed to countering a massive Soviet nuclear attack. It is not designed to thwart an attack by contemporary Russia, with its much reduced but still very large strategic missile inventory. Nevertheless, robust BMD capabilities, actual or prospective, will necessarily have implications for America's strategic relationship with Russia and other current nuclear powers, as well as for international security more broadly. We will return to these important issues in a moment. First, though, it may be useful to restate the case for a limited American BMD system in our current security environment.

Why We Need It

Former Director of Central Intelligence George Tenet recently warned of the growing appetite of second-tier states for nuclear weapons and the weakening of international controls on them. Most dramatically, North Korea's break with the international non-proliferation regime in January 2003 and its preparations for resuming plutonium production in early March of that year seemed to make inevitable--barring unilateral military action by the United States, which seems highly unlikely at the present time--Pyongyang's emergence in the very near future as the classic "rogue state" possessed of nuclear-armed, long-range ballistic missiles with at least some capability to threaten the continental United States. Iran also appears determined to acquire weapons of mass destruction (WMD), in particular nuclear weapons, and the United States and its allies have become increasingly alarmed about the scale of the clandestine nuclear program it is pursuing in contravention of international safeguards.

In addition, only recently has it become clear to what extent the nuclear programs of North Korea, Iran and also Libya benefited from the technical assistance they received over many years from the putative renegade Pakistani scientist A. Q. Khan, the founder of Pakistan's own long-standing nuclear program. There is also some evidence that the Pakistanis may have worked out a secret agreement with Saudi Arabia to share nuclear weapons technology or missile systems.