"So far, Mr. Putin has indicated that his goal for Ukraine is a federal structure in which the provinces would have considerable autonomy from Kiev, plus some constitutional guarantees that Ukraine would not join NATO. The secessionist turmoil in Donetsk and elsewhere may be intended to pressure Kiev into an arrangement suitable for Moscow. There is a danger, of course, that Russia would seek to dominate the eastern and southern provinces that were the industrial core of the Soviet Union, but Ukrainian leaders have agreed that some degree of constitutional decentralization is needed, and it is for Ukraine to decide its organization.
Mr. Putin has awakened passions that even he may not be able to control. It is easy to imagine how secessionist demands in Donetsk, Kharkiv or Luhansk could turn violent, compelling Mr. Putin (or giving him a pretext) to make good on his pledge to “defend” Russians in Ukraine. The next Western response must be ready and credible, and that means, above all, that the Europeans have to look beyond their internal problems and join Washington in agreeing to a package of extensive and strong sanctions that can be put in place immediately should that be necessary, including restricting the access of Russian banks and corporations to Western financial markets.