It may seem that the response of the U.S. and European Union to Russian President Vladimir Putin’s Soviet revanchism is entirely ad hoc and reactive. There is, however, a logic to it that even Putin appears to accept, if not acknowledge, which is that Europe has in effect been divided into three castes.

The lowest of these castes, as seen from the capitals of Western Europe, consists of countries in the former Soviet Union’s southern underbelly. If Russia attacks or bullies these, the only reaction is dismayed noises.

This was the case, for example, when Russian troops invaded Georgia, in 2008. Similarly when Armenia, under intense Russian pressure, turned down an association agreement with the EU in 2013, there was no visible EU attempt to push back. So the ex-Soviet countries in Central Asia and the Southern Caucasus appear in practice to be recognized as part of Russia’s sphere of influence.

If, however, Russia meddles in a country that is considered fully European, even though it isn’t part of the EU or the North Atlantic Treaty Organization, that’s more worrisome. As Swedish Foreign Minister Carl Bildt, one of Moscow’s harshest critics, said in a speech in June in Berlin:

What we are facing is thus our vision of a Europe of peace and stability built on firm principles accepted by each and every one being confronted with a power seeking a revision of the order we have been trying to build. Revising the borders. Revising the principles.

On this interpretation, Europe as a geographical entity is different from those other, non-European places, because it has been the arena of conscious postwar efforts to build a security consensus. What Bildt calls Russia’s “macho nationalism” in Europe is, as we have seen, punishable by a major public relations offensive and a spate of ineffectual economic sanctions that end up hurting both sides.

Then there is the third and highest caste — “real” Europe, as defined by inclusion in the EU, NATO or both, and for which the U.S. and its closest allies are willing to fight.

So although in 1994, for example, the U.S. and the U.K., together with Russia, affirmed their commitments to Ukraine’s territorial integrity in exchange for Ukraine’s agreement to give up nuclear weapons, the wording of the Budapest Memorandum did not oblige them to do anything if the newly disarmed country should be attacked. NATO’s founding treaty, by contrast, clearly states that “an armed attack against one or more of them in Europe or North America shall be considered an attack against them all.”

True, the famous Article 5 clause doesn’t actually commit signatories to use military force to meet this all-for-one obligation — it requires each NATO member to take “such action as it deems necessary.” Still, U.S. President Barack Obama wants NATO members to believe they are reliably protected.

“We’ll be here for Estonia,” he said in Tallinn last week. “We’ll be here for Latvia. We’ll be here for Lithuania. You lost your independence once before. With NATO, you’ll never lose it again.”

This three-caste system is the common ground between Putin on one side, and the EU and U.S. on the other.

While Putin feels free to interfere as he pleases in the southern part of the former Soviet Union, in Ukraine he has felt compelled to play the deniability game, opting for hybrid warfare to obfuscate his intentions.

Putin could have done to Latvia what he’s doing to Ukraine. The Baltic country, which lost 15.5 percent of its population between 1990 and 2010, mostly to emigration within the EU, is home to a 40 percent ethnic Russian minority.

Of Latvia’s 2 million population, 281,000 are disenfranchised “noncitizens,” whose families moved to Latvia during the Soviet era and can only acquire citizenship if they pass language and history tests.

Fomenting unrest among this disenfranchised population, and perhaps even starting an armed rebellion as in eastern Ukraine, would have been possible with the right investment. Putin, however, has chosen not to do that, perhaps recognizing the red line NATO has established.

Whether he will test NATO’s commitment depends on the degree of practical commitment on the part of alliance governments. They must make sure that whatever “spearhead force” or bases they put in the Baltics are sufficient to convince Putin that U.S. and German soldiers would go to war should he attack, including through hybrid tactics. Almost as important is to quickly integrate the “noncitizens” — Estonia has 93,000 — into the Baltic nations and the EU market.

Only then will these countries become safely birthed in Europe’s charmed third circle.

Leonid Bershidsky is a Bloomberg View contributor. He is a Berlin-based writer, the author of three novels and two nonfiction books. Bershidsky was the founding editor of Russia’s top business daily, Vedomosti, a joint project of Financial Times and the Wall Street Journal, and the first publisher of the Russian edition of Forbes.

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