The decision by NATO members last week in Bucharest to endorse American plans for a third missile-defense site located in Europe represents a huge step forward for the alliance and for American and European security. It is an achievement for American diplomacy that many thought was beyond reach.

Russia, which is not a member of NATO but has a "partnership" agreement, fiercely opposed American missile-defense plans, but its bluster was ineffective. It did succeed in pressuring Europeans to oppose Georgian and Ukrainian membership action plans for NATO, but on missile defense, the Russians lost big.

At the ensuing Black Sea Summit between President Vladimir Putin and President Bush, Mr. Putin snippily turned away Mr. Bush's offer to share missile defense with the Russians. Let him be offended. The Russians cannot do a thing about the decision of sovereign nations to defend themselves against the ever-growing dangers of worldwide missile and nuclear proliferation.

Russian opposition to missile defense is unjustified on factual grounds, but this does not mean it is irrational. Russians do not have anything to fear from the unarmed American missile-defense interceptors, which will be stationed in Poland with a new radar installation in the Czech Republic (in addition to existing U.S. radars in Britain and Greenland). Nevertheless, defeat on missile defense has huge symbolic value for the Russian government, as the same issue played a key role in the fall of the Soviet Union.

By coincidence, the NATO summit coincided with the 25th anniversary of then-President Reagan's announcement of the Strategic Defense Initiative. Critics here in the United States immediately derided Mr. Reagan's plans as so much science fiction. Yet, the news of SDI sent chills down the spine of the Soviet leadership. The situation back then was reminiscent of today's engagement in Iraq, which is understood to be the central battlefield by al Qaeda leaders, but derided at here at home as a diversion by many Democrats.

Just how seriously the Soviets took SDI was on display at the 1985 Reykjavik summit between Presidents Reagan and Mikhail Gorbachev. Mr. Gorbachev proposed the most drastic cuts in nuclear weaponry the world had ever known - a halving of the numbers of Soviet and American missiles - if only Mr. Reagan would give up SDI. At that point in time, SDI existed only on the drawing board, so the offer was startling. In fact, Mr. Gorbachev's offer was so dramatic that it immediately confirmed Mr. Reagan's faith in his own idea. If SDI meant that much to the Soviets, it should at least mean as much to Americans. Showing courage that few political leaders would have, Mr. Reagan walked away from the table.

Back at the Kremlin, the Soviet Politburo obsessed over SDI, even though Russia itself had built a limited missile defense around Moscow in contravention of the Anti-Ballistic Missile Treaty between the United States and the Soviet Union. The Soviet Union during the 1980s was spending 25 percent of its gross domestic product on its military and was bankrupting itself. It simply could not afford to spend more.

The United States, by contrast, thanks to Mr. Reagan's economic policies, was booming and was only spending 6 percent on its military and could easily afford to spend more. Mr. Gorbachev knew that the Soviet Union was facing an existential moment in its life. Only a few years later, the Berlin Wall came tumbling down.

Can anyone doubt that the current Russian leadership is mindful of this humiliating recent history? Mr. Putin has been looking over the writings of Russian political philosophers and historians to find a founding philosophy for his resurgent nationalist Russia, and he surely will not have missed the historical significance of SDI.

Not only does it mean that the United States remains in a leadership position in Europe, but it also points up the fact that the sheer size of the U.S. economy dwarfs that of Russia's, even in a time of booming Russian energy exports. We can afford to spend far more on missile defense than we do.

Some will argue that rubbing the Russian leadership the wrong way is a serious mistake. Yet at this point in time, it is clear that Russia under the influence of Mr. Putin - though he will not nominally hold the power of president - will look after its own interests. The United States and its allies should never shy away from doing the same.

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