Risk of a Ukraine war spreading in Europe rests on unknowns

A Russian invasion of Ukraine would be devastating, and a wider European war even worse. Whether a larger war happens would depend partly on President Vladimir Putin's ambitions, partly on the West's military response, and partly on plain luck.

Although U.S. and European officials have said for days that a Russian invasion appeared imminent, Putin's government on Tuesday publicly welcomed further security talks with the West. It also announced that some of its forces bracketing Ukraine will be returning to their regular bases, although U.S. and other Western officials said it was too early to tell whether the invasion threat had receded.

War by its nature is unpredictable, and the stakes are enormous, not just for an overmatched Ukraine but for Europe and the United States. At risk, arguably, is the European security order established after World War II and then altered peacefully with the reunification of Germany, the demise of communism in Eastern Europe, the collapse of the Soviet Union and the expansion of NATO.

President Joe Biden has said he will not fight Russia in Ukraine, nor would America's NATO allies. So a Russian invasion would not automatically trigger a wider war. But if Putin took his offensive beyond Ukraine's borders onto NATO territory, the United States could get drawn into it. That's because Washington is obliged by the North Atlantic Treaty to defend its allies, some of whom fear they are Russian targets.

"Make no mistake. The United States will defend every inch of NATO territory with the full force of American power," Biden said Tuesday. "An attack against one NATO country is an attack against all of us."