Russia is sending a message intended not only for Ukrainian ears. It’s a threat to all former Soviet nations. As such, it’s a challenge to the United States—and we need to be very clear about what that challenge is, and what it means.

Tell me if you’ve recently heard a pundit or strategist say something like the following:

Russia is a great power. It is entitled to a sphere of influence on its borders. NATO and the European Union pushed Russia too hard while Russia was weak. Russia is stronger now, and so naturally it’s pushing back. We have to understand Russia’s need for friendly governments on its border.

Familiar, right? Now let’s consider why it’s an awful thing to say.

Every great power, of course, wants friendly neighbors. But the surest way to secure friendly neighbors is to be friendly yourself. It didn’t just happen that Germany is bordered by a friendly France to the west and a friendly Poland to the east. Germany has earned that friendship with its constructive policies in the years since World War II. Germany doesn’t need to subvert French and Polish democracy to ensure French and Polish friendship. Nobody can win an election in France or Poland on a platform of hostility to Germany.

If Russia finds itself in a different situation, it’s because of Russia’s own actions. Russia’s neighbors are frightened of Russia because Russia is frightening. Rather than allay those neighbors’ concerns, Moscow tries to manipulate neighboring political systems and install stooge governments. Neighbors a little further away—Poland, for example, or the Baltic republics—have every reason to worry that Russia would do the same to them, if it could.

But it can’t. And that’s because of the security guarantees enjoyed by NATO members. As a result of that guarantee, Europe—from Estonia westward—is a more peaceful place than ever before in its history. Ukraine is not in NATO; the alliance’s leaders decided that was one extension too many, for reasons both good and bad. Among the good was the rationale that we couldn’t fully rely on the Ukrainian government and military to behave like a proper NATO partner. Ukraine’s officials were too corrupt and easily swayed by Russia; its population’s loyalties too uncertain; and its military capabilities too inadequate. Among the bad were the kinds of arguments summarized in the italicized paragraph above.

The events of the past two months have upended that calculus. A more honest and accountable government in Kiev may follow Viktor Yanukovych’s ousted regime, though reform in Ukraine is no sure thing. We owe this opportunity to an ironic benefit of Russia’s attack on Ukraine: a surge of nationalism. During my recent visit to the country, I met many Russian-speaking Ukrainians who regard Vladimir Putin as a tyrant and aggressor. One senior Ukrainian government official estimated that 40,000 Ukrainians had enlisted in the national guard, though others put the figure somewhat lower.

Realistically, though, Ukraine cannot successfully resist Russia on its own. It needs help, and the West should provide it. “I really think you are more afraid of Russia than we are,” said the same senior official who told me about the enlistments. NATO’s power vastly exceeds Russia’s, and Barack Obama is right to call Russia merely a “regional power.” Yet when it comes time to make policy, his administration seems to lose sight of the president’s insight.