It's easy to get a bit complacent on the security front these days. We've gone seven years without a terrorist attack on U.S. soil, and we're seeing progress in Iraq as well. But we still live in a dangerous world.

Russia's invasion of Georgia reminds us that the former U.S.S.R. still has plenty of military might and the will to use it against its neighbors. Meanwhile, Iran seems eager to obtain ballistic missiles that could threaten Europe, and nobody has any idea what may happen in nuclear North Korea.

Luckily, with the help of our allies, our military is responding to the growing threats.

In August Poland agreed to base interceptor missiles on its territory. These are completely defensive weapons, but could go a long way toward deterring a potential Iranian offensive. These missiles will work in conjunction with radars deployed in the Czech Republic.

The step comes just in time. Even though it's difficult to be sure how advanced the Iranian missile program is, we know it'll take about five years to get our defensive screen in place and fully operable. So it seems likely that, by the time Iran could be in a position to threaten our allies, we'll have a working defense to protect them.

Often, just having defense in place can prevent an enemy from bothering to invest in an offensive weapon. If Iran realizes that American land- and sea-based missile defenses could shoot down any missiles it launched, it may well decide not to bother going ahead with its missile-building scheme.

Iran wouldn't be the first country to decide nuclear weapons are more trouble than they're worth. Brazil, South Africa and Libya all had nuclear ambitions, once, but abandoned their programs. Even if Iran presses ahead, once the defensive missiles are in place, the United States and our European allies will have enough troops and missiles to deter Iran.

The missile-basing agreement also matters because it shows the U.S. is ready and willing to stand alongside the Poles and Czechs. After all, our own defense soon will be tied directly to their defense. Perhaps that cooperation explains is why Russia so adamantly opposes the missile-defense screen.

Of course, our missiles will pose no threat to Russia. They're defensive weapons, not ones that would be used in an attack. Moscow knows this. And Russia has so many hundreds of missiles, it could easily overwhelm a defensive screen, if it choose to launch a massive missile attack against Europe.

Still, by placing defensive missiles that Moscow opposes on Polish soil, NATO and Poland are sending a message that we're serious about the Iranian threat, and that we're willing to stand against Russia when it overreaches.

That's exactly what our old Cold War foe did last month by invading democratic Georgia and claiming to have annexed regions of it. And it's no coincidence that, almost immediately after that invasion, the Polish government officially agreed to allow the missile bases. There's no reason for anyone to expect Russian bellicosity to stop at the Georgian frontier, and the Poles are smart to want more secure ties with NATO and the U.S.

The U.S. needs to act, too.

Lawmakers here should show their support for expanding missile defense by passing a "sense of the Congress" statement that endorses the rapid deployment of missile defenses in Europe. They also should restore the cuts made to the Bush administration's annual appropriation request for missile-defense programs.

Yes, we live in a dangerous world. But a strong missile defense can make that world safer, by reminding untrustworthy regimes that unprovoked aggression won't stand.

Ed Feulner is president of The Heritage Foundation (heritage.org).