The allure of the West has helped shape Russian history since Peter the Great three centuries ago. Now it’s shattering even older bonds with Russia's neighbor, Ukraine. In 2013, a rebellion sparked by pro-European Ukrainians seeking a decisive break from the nation’s Soviet past set in motion a chain of events that created the tensest standoff between Russia and the West since the Cold War. Russian President Vladimir Putin annexed Ukraine’s Crimean peninsula in March 2014, proclaiming a duty to defend the ethnic Russians who dominate the population there and sending shockwaves through the post-World War II order.