On Sept. 5, 2014, Russian agents crossed into Estonia and kidnapped an Estonian security official. Last week, after a closed trial, Russia sentenced him to 15 years.

The reaction? The State Department issued a statement. The NATO secretary-general issued a tweet. Neither did anything. The European Union said it was too early to discuss any possible action.

The timing of this brazen violation of NATO territory – two days after President Obama visited Estonia to symbolize America’s commitment to its security – is testimony to Vladimir Putin’s contempt for the American president. He knows Obama will do nothing. Why should he think otherwise?

• Putin breaks the arms embargo to Iran by lifting the hold on selling it S-300 missiles. Obama excuses him, saying it wasn’t technically illegal and adds, with a tip of the hat to Putin’s patience: “I’m frankly surprised that it held this long.”

• Russia mousetraps Obama at the 11th hour of the Iran talks, joining Iran in demanding that the conventional-weapons and ballistic-missile embargos be dropped. Obama caves.

• Putin invades Ukraine, annexes Crimea, breaks two Minsk cease-fire agreements and erases the Russia-Ukraine border. Obama’s response? Pinprick sanctions, empty threats and a continuing refusal to supply Ukraine with defensive weaponry, lest he provoke Putin.

The Eastern Europeans have noticed. In February, Lithuania decided to reinstate conscription, a move strategically insignificant – the Lithuanians couldn’t hold off the Russian army for a day – but highly symbolic. Eastern Europe has been begging NATO to station permanent bases on its territory as a tripwire guaranteeing a powerful NATO/U.S. response to any Russian aggression.

NATO has refused. Instead, Obama offered more military exercises in the Baltic States and Poland. And threw in 250 more tanks and armored vehicles, spread among seven allies.

It is true that Putin’s resentment over Russia’s lost empire long predates Obama. But for resentment to turn into revanchism – an active policy of reconquest – requires opportunity. Which is exactly what Obama’s “reset” policy has offered over the past 6½ years.

Since the end of World War II, Russia has known that what hinders westward expansion was not Europe, living happily in decadent repose, but the United States as guarantor of Western security. Obama’s naïveté and ambivalence have put those guarantees in question.

It began with the reset button, ostentatiously offered less than two months after Obama’s swearing-in. Followed months later by the unilateral U.S. cancellation of the missile shield the Poles and the Czechs had agreed to install on their territory. Again, lest Putin be upset.

By 2012, Obama mocked Mitt Romney for saying that Russia is “our No. 1 geopolitical foe.” After all, he explained, “the Cold War’s been over for 20 years.”

Obama’s own top officials have been retroactively vindicating Romney. Last month, Obama’s choice for chairman of the Joint Chiefs of Staff declared that “Russia presents the greatest threat to our national security.” Two weeks ago, the retiring Army chief of staff, Raymond Odierno, called Russia our “most dangerous” military threat. Obama’s own secretary of defense has gone one better: “Russia poses an existential threat to the United States.”

Turns out the Cold War is not over, either. Putin is intent on reviving it. Helped immensely by Obama’s epic misjudgment of Russian intentions, the balance of power has shifted – and America’s allies feel it.

And not just the Eastern Europeans. The Saudis, congenitally wary of Russia but shell-shocked by Obama’s grand nuclear capitulation to Iran, recently invited Putin to Riyadh. The Russians reciprocated by inviting the new King Salman to visit Czar Vladimir in Moscow.

Even Pakistan, a traditional Chinese ally and Russian adversary, is buying Mi-35 helicopters from Russia, which is building a natural gas pipeline between Karachi and Lahore.

As John Kerry awaits his upcoming Nobel and Obama plans his presidential library (my suggestion: Havana), Putin is deciding how to best exploit the final 17 months of his Obama bonanza.

The world sees it. Obama doesn’t.

Charles Krauthammer is a columnist for The Washington Post. He can be contacted at:

letters@charleskrauthammer.com