Though the fear of imminent war has receded, the Middle East has been profoundly destabilised by the American assassination of Iranian General Qassem Soleimani. The unfolding US-Iran conflict will impact the whole region, not least Iraq, where the Iranians are intent on hastening the end of America\u2019s military presence. Stephen Sackur interviews Douglas Silliman, former US ambassador to Iraq until a year ago. Does Trump have a strategy - and if so, what is it?