The Post reports: “Several hundred armed men in green camouflage, without insignia and carrying military-style automatic rifles, entered and secured areas of the civilian airport in Crimea’s regional capital of Simferopol early Friday. Video taken at the scene showed the men patrolling inside the airport and standing guard outside. Flights continued to operate; no shots were fired. In Kiev, Ukraine’s new interior minister, Arsen Avakov, said the armed men were Russian troops.”

This is a sobering turn of events. After repeated public warnings from the Obama administration not to move militarily against Ukraine, Vladimir Putin appears to have done just that. And why wouldn’t he? One can imagine in that hour-long conversation between President Obama and Putin last week, Putin took the measure of the man and found him to be a push-over.

The president keeps telling the world that he doesn’t see this as a Russian problem. The idea of returning to the Cold War — when we checked Soviet expansion and stood up for free peoples — is anathema to Obama. With massive Pentagon cuts, the withdrawal of U.S. troops from Afghanistan, a prominent senator decrying efforts to brush back Russia (“tweak”) and evisceration of the Syrian “red line,” Putin has made an entirely rational calculation that he can destabilize Ukraine or, at the very least, exert Russian domination over Crimea, with very little if any consequence.

Some context is useful here. Former U.S. ambassador to the United Nations John Bolton reminds me that when President George W. Bush tried to get Ukraine and Georgia on a clear path to NATO membership, “Europe balked because of … fear of the Russian reaction.” He says, “That’s a fine irony.” Obama, by contrast, strong-armed Georgia into dropping its objections to Russia joining — condition-free! — the World Trade Organization.

Russia, of course, has a long history of moves like this. Anne Applebaum writes, “Russian agents successfully undermined the sovereignty of Georgia by offering Russian passports and other inducements to the residents of South Ossetia, a Georgian province, and then carrying out a de facto invasion. The same kinds of tactics were used to create the semi-autonomous province of Transnistria. Technically part of Moldova, Transnistria lives its own post-Soviet life under de facto Russian control.” Staged provocation, association with local pro-Russian elements calling for Crimean “separatism” from Ukraine and economic bullying can and likely will be used to sweep Ukraine into Russia’s orbit. (“The destabilization of Ukraine may only have just begun. The events in Crimea might only be the first act,” writes Applebaum.)

Many critics of the president assume that he will do next to nothing about Russian aggression. We are not without tools, however. A more deft administration could lead the Europeans in devising an economic package to keep Ukraine afloat (including the supply of energy). We can and should expose Russian meddling; some leaked phone calls between the Kremlin and Ukraine might be quite appropriate here. And we could actually take Russia provocation seriously and take limited but noticeable economic or diplomatic action against Russia. (How about finally taking Russia to task for violating existing arms agreements?)

Other foreign policy gurus stress that we should prevail upon Ukraine to reassure Moscow that it is ready to build a decent relationship with the Kremlin. Ukraine is just too weak and has so many internal problems that it cannot afford, as one expert put it, “a full-scale geopolitical rumble with Russia.”

All too frequently, Obama has things entirely wrong. This is about Russia and whether the West has the will and ability to keep Europe free and whole. Every president since George H.W. Bush has been committed to and has succeeded in that objective. Obama may be the first to fail. The list grows ever longer: Who lost Syria, Ukraine, Iran (stiffing the Green Revolution and allowing that country to go nuclear), the states of the Arab Spring and maybe Venezuela? Obama, whose presidency would go down as an “historic” and utterly failed one.

UPDATE: Another foreign policy and human rights expert remarks that Russia likes to undertake these things “in the dark.” Public discussion at the United Nations Security Council and elsewhere, with participation by the French, British and other key allies would force Putin’s skullduggery into the open. Likewise a high level visit from the secretary of State would be a morale booster.