Since a commercial airliner crashed in eastern Ukraine on Thursday — brought down, in all likelihood, by a pro-Russian militants — Russian president Vladimir Putin has cast the blame solely on Ukraine’s government, saying it “bears responsibility” for the deaths of close to three hundred passengers and crew.

With the separatist insurgency seemingly at an impasse and Russia’s most important European trading partner, Germany, warning on Saturday that this is Putin’s “last chance,” after it previously resisted sanctions, why won’t the Russian leader back down?

Since Russia invaded Ukraine and annexed the Crimea in March, following mass protests in Kiev that toppled the relatively pro-Russian president Viktor Yanukovich, it has accomplished little more than uniting the vast majority of Ukrainians and world opinion against it.

In the months leading up to Yanukovich’s resignation, Russia had tried to dissuade Ukraine from entering into an association agreement with the European Union, hoping to lure the former Soviet republic into its own Eurasian Union with Belarus and Kazakhstan instead. When Yanukovich budged to Russian pressure, he was promptly ousted. His successor, Petro Poroshenko, who was elected in May on a promise to put down the uprising in the east, signed the European treaty last month, putting Ukraine on a track to membership.

The separatists in southeastern Ukraine, inspired by what happened in the Crimea, still hope Russia will annex them. But Putin has given no indication he intends to. Rather, he formally renounced the right to intervene militarily in Ukraine last month, a permission he had been given by the Russian Senate, although Russian support for the rebels appears to have continued since.

To what end?

Daniel Berman, a PhD candidate at the London School of Economics, argues at The Restless Realist that Putin finds himself trapped. “There is no clear political objective behind the separatist campaign that Moscow can sell as a victory,” he suggests, “but their abandonment would almost certainly lead to a clearcut defeat.”

A defeat for the rebels, or a withdrawal of Russian support, would be seen as a defeat for Russia as well, “roughly equal in significance to the victory in Crimea,” writes András Tóth-Czifra, a political scientist who blogs about Russian politics.

Russian propaganda has so strongly made the separatists’ case, claiming they are rightly fighting for their identity and language in the face of a “fascist” regime in Kiev bent on oppressing them, that one in four Russians would support military intervention in Ukraine — up from 31 percent in May.

Western condemnations are unlikely to change those numbers. Many Russians support Putin’s policy because they see him as standing up to their old enemy, the United States.

As Tóth-Czifra puts it, “Vladimir Putin has no choice, internationally, but to immediately and distinctly cease supporting separatism in eastern Ukraine. And he has no choice, domestically, but to cling on to it.”

The Malaysia Airlines crash has only put Putin in a tougher spot, adds Berman. He must now decide “between appearing callous and strong or compassionate and weak.” His statements blaming the Ukrainian government and Russian media’s conspiracy theories suggest he has opted for the former. Putin might know it were the rebels who shot down the plane but there is nothing he can do about it. Russia has lost control over the insurgency it helped create.

“What he can do,” according to Berman, “is give the impression that Russia neither cares nor can be touched by the fury of foreigners, which will serve the purpose of focusing the Russian public’s anger at the Western countries who will condemn Russia’s actions rather than on the policies that brought about the downing.”