Why has the post-Cold War era given way to a world in which Russia challenges the United States in every corner of the globe? And how as Russia again become such a toxic and divisive subject in US politics? After the break-up of the Soviet Union it looked all so promising: a pro-west and open Russia seemed to be possible. Russia expert Angela Stent examines the country's turbulent past, how it has influenced Vladimir Putin, the Russians' understanding of their position on the global stage and their future ambitions.