That shield, not a sword: how goes Ronald Reagan's goal of anti-ballistic-missile defenses?(DEFENSE)

THE uproar over the expected North Korean missile test brings the question of missile defense, once again, to the fore. Before Ronald Reagan gave his 1983 "Star Wars" speech, both Democrats and Republicans believed that the only way to counter the USSR's nuclear threat was to deter aggression with an arsenal of our own while negotiating (dubious) arms-control agreements. Since then, the GOP has been the pro-missile-defense party, and the Democrats have remained mostly opposed.

After launch, a nuclear missile is most vulnerable in its boost phase, when moving at relatively slow speeds and releasing a huge amount of heat that makes it easy to target. But it can also be intercepted in its mid-course phase, when the warheads, along with any decoys, have been deployed; and in its terminal phase, when the warheads dive toward their targets and the decoys burn up in the atmosphere. Reagan's Strategic Defense Initiative included ideas that would intercept missiles in all three phases.

In spite of limited budgets and the ABM treaty's restrictions on testing and development, the Strategic Defense Initiative Organization (SDIO) made impressive progress. It found that a space-based defense that could hit a missile in its boost phase was technologically possible. This project, known as Global Protection Against Limited Strikes, was ready to move into testing and production in 1993, when it was canceled by Bill Clinton's first defense secretary, Les Aspin, who reportedly boasted that he was going to "take the stars out of Star Wars."

The 1994 midterm election changed everything. GOP leaders, now in the majority, pushed hard for Reagan's vision. Clinton, recognizing the political futility of openly opposing missile defense, decided to let the SDIO (now renamed the Ballistic Missile Defense Organization) proceed with plans to build a basic missile defense while keeping within the limits of the ABM treaty. The primary focus of this project was to be a ground-based interceptor that would hit warheads in mid-course, the phase in which they are hardest to target.

George W. Bush took office in 2001 committed to building a missile-defense system "as soon as technologically possible." His new secretary of defense, Donald Rumsfeld, had chaired two panels on missile defense and military space activities. One of those, the Commission to Assess the Ballistic Missile Threat to the United States, had concluded in 1998 that "the threat to the U.S. posed by [enemy missiles] is broader, more mature and evolving more rapidly than has been reported in estimates and reports by the intelligence community." The commission estimated that North Korea's Taepo Dong 2 missile could reach Alaska and parts of Hawaii. It also wrote that a lightweight version of the same missile could place at risk "western U.S. territory in an arc extending northwest from Phoenix, Arizona, to Madison, Wisconsin." It noted that Iran was moving forward rapidly with both missile and nuclear-weapon technology. Finally, it said that these states had the ability "to deceive the U.S. about the pace, scope and direction of their development and proliferation programs."

After 9/11, it became clear that the U.S. could not take any chances. It is sometimes said that missile defense has nothing to do with terrorism, but that claim loses plausibility as Iran, the world's greatest terror sponsor, pursues both nuclear weapons and advanced missile technology. In December 2001, Bush decided to scrap the ABM treaty and proceed with an unrestricted version of Clinton's missile-defense plans. Despite a number of test failures, the Ballistic Missile Defense System is now in place in rudimentary form. It includes ground-based interceptors in Alaska and California under the Army's 100th Missile Defense Brigade. A number of highly effective SM-3 sea-based interceptors, which can be launched from Aegis cruisers and destroyers, are also part of the system. Meanwhile, we are making good progress on the Terminal High Altitude Area Defense system, which will supplement our Patriot missiles. Also promising is an airborne laser, mounted on a Boeing 747, that will be able to hit Scud-type missiles in their boost phase. But it's unlikely that either of these systems will be ready before 2010.

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