Missile Defense Systems

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Experts have long debated the idea of defending national territory against airborne strategic attack. These debates often conflate feasibility, morality, strategy, and politics, so that each observer must independently weigh such factors even in arguments that seem to be purely technical.

BMD (ballistic missile defense) supporters tend to draw on early strategic theory developed by Wohlstetter (1958) and others from the RAND Corporation (for example Kahn 1970). They generally suggest the following: Nuclear strategy is neither easy nor impossible. It requires repeated analysis and improvement. It should serve national policy, such as deterring enemies (or the nation should change its policy). National leaders have a commitment to preserve and protect the people and the political system as well as they can, which no technical advice can abrogate. Deterrent systems should maximize human control over weapons. Deterrence based on the threat of retaliation against civilians is immoral if targetting enemy weapons is possible. Furthermore, the strongest supporters of BMD tend to have more faith in large-scale technology development and system predictability and performance.

BMD critics, in contrast, generally believe the following. Nuclear weapons are so awful and so difficult to stop that their development should freeze in place and that arms control diplomacy should be relied on to reduce them. Even one or a very few nuclear weapons detonated in war would be as bad as many, so that targeting a few against cities is enough to threaten assured destruction (AD) to any potential attacker, thereby achieving deterrence and stability. No defense is likely to prevent some attackers from getting through to cause unacceptable damage.

In this view, offense dominates defense. Defenses undermine stability and encourage useless competitive arms procurements ("arms races"). Measures to reduce the consequences of nuclear war will only encourage it. These critics accept mutual deterrence based on the threat of retaliation, to the point in the 1970s of considering a policy of [immediate] "Launch-On-Warning" or "Under Attack" (Garwin 1989, pp. 189–198). Therefore, they advocate cooperating with adversaries against a greater and common enemy, the danger of nuclear war, by accepting mutual vulnerability (Carter and Schwartz 1984).

Whatever the value of any of these views on either side, they often have combined technical, strategic, political and ethical beliefs in ways difficult for observers to evaluate. This problem caused one professional society to conduct a formal—and critical—review of the professional standards at work (ORSA 1971).

Historical Development of Arguments

While the debate from the 1960s to the present has focused on ballistic missile threats, strategic defenses may target any air-borne attacker. Strategic defense may use active means such as interceptor weapons and passive means such as hardening (protecting), hiding, and dispersing assets against enemy targeting. After German dirigibles bombarded London during World War I, thinkers from the English writer and futurist H. G. Wells to the U.S. Army Air Corps predicted that future wars would be dominated by air power, which would be "strategic" more than "tactical": It would aim at national will, not forces, by attacking the enemy cities to force the population to demand that its government sue for peace. Defenses could not stop "the bomber always getting through," and only a few bombs would be enough to achieve the strategic goal. Therefore, nations should ignore defenses and rely for security on their own bombers to threaten retaliation. Yet in 1940 the Battle of Britain saw Royal Air Force fighter defenses stop enough German bombers to defeat their strategic purpose, even if many bombs indeed "got through."

The atomic bomb revived the idea that devastating attack was unavoidable, and therefore the only means of stabilizing relations was to threaten retaliation. Some even argued that the analysis of the military use of nuclear weapons was immoral and "unthinkable" because it might make nuclear war seem rational.

After World War II, many technologists involved in the development of atomic weapons helped pioneer this debate (Kimball Smith 1965). Radar expert Louis Ridenour, in a collection (Masters and Way 1946) for the nascent Federation of American Scientists immediately after the war, described the great difficulty of countering each aspect of an airborne attack, making defense hopeless. Such arguments have become standard, as in those made by leading assured destruction theorists and BMD critics such as Richard L. Garwin (1989) and others (for example UCS, 1984).

This view reached its peak in 1972, when the United States and the Soviet Union pledged in the Anti-Ballistic Missile Treaty (ABMT) not to defend against each other's missile threat, arguably making further offensive weapon development superfluous. The two powers accompanied the ABMT with a Strategic Arms Limitation Agreement capping offensive forces at some 1,700 U.S. missiles and almost 2,500 Soviet missiles, numbers that diplomats expected to reduce in future negotiation.

These missile levels were more than enough for AD theorists. They saw the only rational use of strategic forces as pure deterrence (threatening cities, if not expecting actually to attack them). They saw military use (targeting forces) as irrational. Cities were good targets because the destruction of enemy cities was easy and of our own, unacceptable. This scenario eliminated both the targeting side's temptation to upgrade its weapons and the targeted side's temptation to make useless, yet still provocative, defenses. A balance of deterrence ensued—"mutual assured destruction" (MAD). Neither side could envision a nuclear war scenario from which it could escape intact. While leaders' acceptance of vulnerability, especially of civilians, might turn ethical traditions on their head, proponents believed they had a better analysis of the dynamics of nuclear peace. With the election of Jimmy Carter to the Presidency in 1976, these views achieved their peak in U.S. policy.

The Soviets, however, frustrated expectations. By 1979, Harold Brown, President Carter's Defense Secretary, told Congress that "Soviet spending has shown no response to U.S. restraint—when we build they build; when we cut they build" (Brown 2003). The Soviets also improved the accuracy of their warheads, which they now mated to their very large boosters. The combination raised the possibility of a disarming first strike—against not U.S. cities but the land-based deterrent forces themselves. Few enough might survive that retaliation would then fall to the submarines and the bombers, in which defense supporters (but not the AD theorists) saw major problems.

BMD Proposals

In 1980 the election of Ronald Reagan to the Presidency signaled a new U.S. skepticism on arms control and assured destruction. President Reagan accepted advice that new technologies based, for example, on directed energy, might create systems that could destroy Soviet missiles, and thereby move zthe basis of deterrence away from mutual threat, toward mutual security. In March 1983, he supported BMD by asking, "Would it not be better to save lives than to avenge them" by countering "the awesome Soviet missile threat ... before they reached our own soil or that of our allies"? Was it not "worth every investment necessary to free the world from the threat of nuclear war?" (Reagan 1983).

Despite strong Reagan Administration support, BMD development programs did not receive similar priority from Congress, the military services, or the subsequent presidencies of George H. W. Bush and (especially) Bill Clinton. In December 2001, however, President George W. Bush announced U.S. withdrawal from the ABM treaty and the intention to develop layers of short-, medium-, and long-range interceptors—air-, sea- and space-based—and the systems to manage them (White House 2001).

BMD nevertheless continued to be controversial. U.S. technical experts, pro- and especially anti-BMD, have often demanded that any BMD system reach extremely high levels of effectiveness. Yet often beneath their arguments there lurk basic questions of technology (will it work?) mixed with policy (should it?). These should be made explicit. For example, BMD "effectiveness" makes sense only in terms of some policy goal. A 100-percent-effective shield may be impossible but also strategically excessive. Alternatively, a defense of three independent layers of say 50-percent effectiveness each, defending retaliatory forces, might make any incoming attack prohibitively expensive if not suicidal. It depends on the strategy.

Attitudes outside the United States

The Russian, Chinese, and North Korean governments oppose BMD because it reduces their threat to the United States and its allies. Beginning in the early 1990s Japanese governments, perhaps as worried by their own pacifists as by China and North Korea, engaged in a delicate and muted dance of cooperative BMD development efforts. The problem is that, if Japan lacks both defenses and a tie to a United States that can credibly defend it, it may well face a choice of acquiescence to its neighbors or developing its own retaliatory forces. Either could be a global disaster.

European experts worried that a U.S. defense system might "decouple" the United States from NATO, make nuclear war more thinkable, or remove constraints on conventional war. Yet lacking a Soviet threat to deter in Europe, the United States relies more on conventional forces to support stability, globally. At the same time rogue states and terrorists have pursued their own mass destruction weapons to deter the Unites States from using its forces. Further European objections to U.S. defenses, therefore, seem more related to intra-alliance political jockeying, resentment at the association of BMD with Presidents Reagan and George W. Bush (neither popular in Europe), and a belief that the ABM treaty is worth preserving as a precedent for arms control.

It nevertheless appears that U.S. BMD work will continue, if only to deny future missiles—from China, North Korea, or anywhere else—an unimpeded ride into the United States. Whatever the validity of AD theory that governed U.S. policy during the cold war, the United States is unlikely to continue to pursue that course alone. While seeking peaceful relations with other powers, it is difficult to see how U.S. leaders will not consider protection against the possible worst case, if only to make it less likely. Missile defenses cannot solve all problems. That they nevertheless try to address some significant ones is likely to capture the attention of leaders.

If these trends hold, the role of the scientists and engineers who have challenged BMD will be essential to ensure that missile defense programs achieve technical, programmatic, and strategic soundness. If both the hopes of BMD supporters and the critiques of BMD detractors are more task-focused and less millennial, their debates will be more transparent, professional, and indeed ethical.


SEE ALSO Computer Ethics;Military Ethics.


Brown, Harold. (2003). Paul C. Warnke Lecture In International Security. New York: Council on Foreign Relations.

Carter, Ashton B., and David N. Schwartz, eds. (1984). Ballistic Missile Defense. Washington, DC: Brookings Institution. See Leon Sloss, "The Strategist's Perspective," 24–48.

Garwin, Richard L. (1989). Richard Garwin on Arms Control, ed. Kenneth W. Thompson. Lanham, MD: University Press of America.

Kimball Smith, Alice. (1965). A Peril and a Hope. Chicago: University of Chicago Press.

Kahn, Herman. (1963). Thinking About the Unthinkable. Croton-on-Hudson: Hudson Institute.

Kahn, Herman. (1970). Why ABM? New York: Prentice-Hall.

ORSA [Operations Research Society of America]. (September 1971). Operations Research 5. "Guidelines for the Practice of Operations Research."

Ridenour, Louis. (1946). "There Is No Defense." In One World or None, ed. Dexter Masters and Katharine Way, 33–38. New York: Whittlesey House, McGraw-Hill.

UCS (Union of Concerned Scientists). (1984). The Fallacy of Star Wars, ed. John Tirman. New York: Random House.

White House. (2001). ABM Treaty Fact Sheet: Statement by the President. Announcement of Withdrawal from the ABM Treaty. Washington, DC: White House Office of the Press Secretary.


Reagan, Ronald. (1984). Announcement of the Strategic Defense Initiative. Available from http://www.nuclearfiles.org/redocuments/1984/841228-reagan-sdi.html.

Wohlstetter, Albert. (1958) "The Delicate Balance of Terror." P-1472. Santa Monica: The RAND Corporation. Available from www.rand.org.

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