Good news from Europe this week. The cause of missile defense took a significant step forward when Secretary of State Condoleezza Rice landed in the Czech Republic to sign an agreement for the Czechs to host a radar system that will become part of the U.S. missile defense system. The agreement signed in Prague represents progress toward a more secure world, and the Czech government has to be commended for its steadfastness in following through on its commitments to the United States.

Another piece of the system, a battery of 10 anti-missile interceptors, is still being considered by the Polish government, on whose territory they would be housed. Negotiations with Poland have been more difficult, as it has persisted in driving an ever harder bargain, including a major package of aid for Polish military transformation and a billion-dollar mobile air defense system.

Statements in June by the Polish defense minister indicated that a deal had been struck with Washington, but the signals have been ambiguous, suggesting another impasse. Meanwhile, the government of Lithuania, next door to Poland and an old historical rival, has suggested that it might be willing to offer its territory if the deal with Poland falls through. This prospect offers a viable alternative.

For the outgoing Bush administration, entering its last half-year in office, progress toward a third missile defense site in Europe is a significant moment. The first two missile defense sites in Alaska and California, which protect the U.S. West Coast, were also hard-won against political opposition here at home, and indeed against skeptics that still contend the system will never work.

The fact that this cause has been advanced at all is to the credit of the Bush White House. As one of its first steps in office, it withdrew from the anachronistic Anti-Ballistic Missile treaty (ABM). It was a courageous political act. After the initial work done by the Reagan administration, the cause of missile defense was abandoned by the administration of the first President Bush and deeply buried during the Clinton years.

The treaty, signed with the Soviet Union during the Cold War, prohibited both signatories from building missile defense systems in the interest of preserving the absoluteness of nuclear deterrence through mutually assured destruction (MAD). (The Soviets never actually abided by the treaty, anyway.) However, as the Soviet Union was long gone by the time President Bush took office, he very reasonably argued that the United States was no longer bound by the treaty provisions.

Why is all this still relevant in today's world, many ask in Europe, now that the prospect for a shield that would also cover them has come a little closer to reality? As is often the case these days, threat perceptions in the United States and in Europe are vastly different.

Unlike the United States, there is little if any debate in Europe about the dangers posed by terrorism, weapons of mass destruction, or ballistic missile proliferation. Though beset by declining demographics, low economic growth and major cultural and social problems attending growing Muslim populations, Europeans generally feel contented and at peace with the world, having entered what many believe to be a final stage of enlightenment within the cozy embrace of the European Union. For Europeans, they are the model for the rest of the world - which in reality, of course, does not bear a lot of resemblance to their well-tended garden.

Quite the contrary. The proliferation of ballistic-missile and nuclear technology is one of the major problems facing the world in the 21st century. Missile defense systems - which have no aggressive aspects and carry no warheads - are reasonable, indeed farsighted, attempts to deal with growing international complexity and instability. The ambitions of countries like Iran, North Korea, and potentially even Venezuela, are a major concern. Furthermore, Russia and China both are investing in their nuclear arsenals - remaining therefore highly critical of U.S. missile defense plans.

How Mr. Bush's legacy will fare under the next U.S. administration is critical as well. Congressional demands for further testing of the system could push deployment back as far as 2013. And while John McCain has indicated that he supports missile defense, Barack Obama has at most stated uncertainly on the issue. It is therefore imperative that the Bush administration continue to push forward on missile defense during its last months in office. Celebrating the progress made in the Czech Republic this week is certainly in order.

Helle Dale is director of the Douglas and Sarah Allison Center for Foreign Policy Studies at the Heritage Foundation.