The drumbeat of war is sounding at the doorstep of eastern Ukraine. In Poland, desperate migrants from the Middle East and Afghanistan had to flee from tear gas and water cannons. And Hungary’s right-wing dictator is cracking down on any hint of dissent. Liberated from the grip of authoritarian rule 30 years ago, Eastern Europe has become a tinderbox — and a headache for U.S. diplomats. Two seasoned experts on the region discuss the latest on these dilemmas, and what America’s role in solving them might be.