There is also the danger that Pakistan's existing nuclear arsenal could fall into the hands of Islamic radicals should that country undergo a revolution or coup, a scenario that is far from outlandish given the internal turmoil created by the government's cooperation with the United States. The acquisition of such capabilities by a revolutionary Islamist regime would be most worrisome for the United States, especially given Al-Qaeda's efforts to obtain such weaponry on its own. And let us not forget the continuing danger of leakage of nuclear weapons, materials and expertise to rogue states and terrorists from Russia and other parts of the former Soviet Union.

Many continue to find comfort in the fact that no rogue states or entities currently possess ballistic missiles of true intercontinental range, even though North Korea is fast approaching such a capability. Yet shorter range missiles could be equally devastating if fired close to the United States. This is, after all, the lesson of the October 1962 Cuban Missile Crisis. Latin America and the Caribbean remain strategically important. The extensive presence in Panama today of a Chinese corporation with links to the People's Liberation Army has attracted little notice, but should at least raise some eyebrows in this context. Hizballah has for some time maintained a significant presence in the hemisphere. Finally, there is the scenario of shorter-range ballistic missiles launched against the United States from nondescript commercial vessels near its shores. We would be defenseless against such an attack.

Yet the greatest immediate threat to American interests posed by ballistic missiles is in fact not to our homeland, but to American forces and friends overseas. In recognition of this fact, as noted earlier, the Administration has formally ceased to draw a distinction between "national" and "theater" missile defense. Defenses against shorter-range, conventionally armed ballistic missiles are an increasingly integral aspect of American overseas power projection capabilities and therefore also of American alliance commitments. By the same token, effective protection of the American homeland against ballistic missile attack, far from encouraging a withdrawal to "Fortress America", can only strengthen the willingness of the American political leadership and general public to take risks on behalf of overseas allies and interests menaced by regional ballistic missile powers.

Two sorts of objections continue to be made to American BMD deployments from the standpoint of what might be called orthodox Cold War-era nuclear strategy. One is that such a step will only stimulate a new arms race either in numbers of offensive missiles or in technical countermeasures that would help them penetrate defenses. The other is that BMD is fundamentally unnecessary because even leaders of rogue states will continue to be deterred from attacking the United States by the threat of U.S. nuclear or conventional retaliation.

The answer to the first objection is that rogue states will have little ability or wherewithal to challenge American defenses, while major powers will not feel sufficiently threatened by the United States to invest large resources in what could well prove a futile competition in any case. It is by no means clear, as critics often assume, that cost considerations will continue to favor offensive over defensive systems--technological developments on the horizon, such as miniature autonomous mid-course interceptors, may well provide a significant cost advantage to the defense. More generally, the Bush Administration's oft-repeated argument that BMD will devalue ballistic missiles and discourage states from expanding their arsenals or acquiring them at all is in fact compelling.

To the second objection, several rejoinders are in order. First, it ignores the possibility of acquisition of ballistic missiles by terrorists lacking a return address and culturally and psychologically resistant to deterrence. Second, it may well overestimate the probability of success of pre-emptive attacks, as well as the likelihood of deterrence failure in the case of a rogue state leader who is actually under attack or has reason to believe an attack is imminent or fears for the demise of his regime. Finally, it ignores the possibility of accidental or unauthorized launch--something that should not be ruled out given the recent history of disastrous accidents in the Russian and Chinese submarine forces. BMD is the strategic equivalent of an insurance policy against unlikely catastrophes.

Costs and Tradeoffs

Persuasive as this case may be overall, there are still legitimate concerns, especially the costs and tradeoffs. As is the case with many experimental military programs, research and development (R&D) and projected operating costs for ballistic missile defense have tended over the years to outpace initial estimates, sometimes by very large amounts. Current spending for BMD R&D, at around $9 billion per year, is relatively modest by Pentagon standards, but acquiring and operating certain BMD systems will in some cases prove very expensive. Space-based systems raise particular questions, especially considering the technical risks, vulnerabilities, and political baggage associated with them. Just the new space-based infrared radar system for missile warning and tracking (STSS, formerly SBIRS-Low) will require a constellation of more than twenty satellites costing upward of $10 billion.

The costs of any defense systems can only be meaningfully analyzed by comparing the costs of systems performing similar missions or meeting other defense priorities. Ballistic missile defense necessarily competes with homeland security requirements that were scarcely on the national agenda before 9/11. Some of these requirements--defense of ports, for example--respond to threats that are at least as plausible as foreign ballistic missiles and could levy very substantial costs in force structure and operating expenses on the U.S. Navy and Coast Guard in the decades to come. BMD also competes with other forms of so-called active defense that meet plausible threats from cruise missiles, unmanned aerial vehicles, and small aircraft--increasingly potent threats even when armed with conventional explosives, due to the spread of precision-targeting technologies.

BMD has never been especially popular within the U.S. military because it has been seen as a competitor for scarce defense dollars, particularly at the expense of the strategic nuclear forces. Though theater BMD has gradually gained acceptance in military ranks as a critical enabler of American forward presence and attack operations, there is still substantial resistance to committing significant resources to national or homeland BMD.

This brings us to the second area of concern. From the 1980s onward, national missile defense in the United States has been driven by an unhealthy combination of technological and political factors. Without denying the necessity of political leadership here, it has to be recognized that the ideological controversies over BMD and the absence of a stable and vested BMD constituency in the military and in industry have resulted in a history of erratic and politically inspired decision-making. At the same time, and paradoxically, they also led to a certain abdication of strategic direction in favor of bottom-up technological experimentation, in an effort to fly under the radar of intellectual and political controversy and to kick key decisions as far as possible down the road. To his great credit, George W. Bush has been willing to take crucial political decisions concerning the future of BMD. It is hard to quarrel with his decision to begin fielding some capability as soon as possible in spite of technical and programmatic risks, given the sorry history of procrastination in this matter, especially during the Clinton years, as well as the gathering threat. At the same time, it is also difficult not to wonder whether technology remains too much in the driver's seat. There is as yet no clearly articulated strategic framework that would provide a basis for doing the appropriate cost-tradeoff analyses and--what is perhaps most important--for reassuring allies and adversaries alike about American intentions in this sensitive and contentious area of international security. Other nations are unlikely to make substantial financial or political commitments to joint technology development with the United States absent a reasonable strategic roadmap.

International Complications

While America's present global dominance will almost certainly rule out classic, Cold-War style arms races, there can be little doubt that Russia and China, as well as other possible adversaries, will explore avenues that offer asymmetric advantages relative to the American defense posture generally. Elements of the Russian military and political elite, for example, view any substantial American BMD effort with foreboding, and are actively seeking to develop ways to counter or neutralize it in order to preserve the viability of their ballistic missiles, which remain the sole effective instrument of Russian global power projection.

Yet, the Russians have already recognized that they have a substantial interest in common with us in discouraging and defeating missile attacks originating in the Middle East--to which they are of course much more directly exposed at present than is the United States. There are interesting possibilities for collaboration with Russia in theater missile defense, and perhaps especially in boost phase systems situated on Russian territory. But we also have to recognize the continuing sensitivity of the Russians to the prospect of a global missile defense capability monopolized by the United States--something that would in their eyes give the United States an unparalleled ability to threaten the security of the Russian state. Accordingly, in the near term we need to explore the possibility of forming a special security relationship with Russia centering on some sort of limited missile defense cooperation, while at the same time demonstrating prudent restraint in the reach of the BMD architecture we decide to develop. This might involve a more or less formal understanding relative to space-based BMD or space-based weaponry in general (on which more in a moment). Over the longer term, when a new generation has taken the reins in that country, the time may arrive when Russian attitudes in these matters are more relaxed.