Russia's grievances define its view of Europe

"France and Germany are used to seeing Russia as one of the major powers in Europe." She says they are used to thinking that, ultimately, "European security matters are settled and decided among the big powers."

But NATO didn't follow that principle after the breakup of the Soviet Union. Russia insists the U.S. promised not to expand NATO and then went back on its word. Many analysts say NATO failed to take Russia's historical anxieties into account.

"If the United States had not spent the past ... 14 years openly declaring that Ukraine would become a member of NATO one day, and not spent the past several years openly talking about Ukraine as if it were a de-facto ally, I think we wouldn't be here right now," says Zach Paikin, a researcher at the Centre for European Policy Studies, a Brussels think tank.

Paikin expresses horror at Russia's brutality in Ukraine, but also says the vast country is a geographic reality that has to be a part of any lasting peace.

"Whether we like it or not, at some point, we will have to address the question of finding an adequate place for Russia in Europe that provides Russia's declared security concerns with a modicum of legitimacy," Paikin says. "Otherwise, we may be forced to inhabit an unpredictable and uncontrollable escalation spiral in our relations with Russia for years to come."