Russia has sent almost 100,000 troops near the Ukraine border in recent weeks. Observers believe the state is trying to extract certain concessions from Europe, particularly assurances from NATO that Ukraine will never be able to join the security group. Janice Gross Stein was a founding director of the Munk School of Global Affairs in Toronto. She argues that NATO’s "strategic ambiguity" toward Ukraine gave the country false hope we had its back — so now, we’re partly seeing the fallout of promises we couldn’t keep.