As Russia masses tens of thousands of troops on its border with Ukraine, along with tanks, artillery and missiles capable of striking the capital, officials in Washington, Kyiv and across Europe are debating the likelihood and timing of an invasion.In one camp, officials in Washington, London and within Ukraine’s national security establishment are convinced that a Russian strike is imminent. But Ukraine’s president, Volodymyr Zelensky, is not persuaded that the intelligence Western nations have shown him backs up their dire assessments.Somewhere in the middle, U.S. allies including France, Germany and Norway think Russia could strike but remain unsure of the...