Can a frantic round of international diplomacy deliver a de-escalation of the Ukraine crisis? The immediate aim is to avoid a shooting war; the long-term challenge is to persuade Russia to accept a new political landscape in Kiev. Can it be done? Stephen Sackur speaks to Ukraine's ambassador to Nato Ihor Dolhov and recently retired US ambassador to Nato Ivo Daalder. In this battle of wills between Putin and the West, who wins?