Foreign correspondent Ruth Michaelson explains how President Bashar al-Assad’s government lost Aleppo, Syria’s second-biggest city, and who the Islamist militants are who have taken control there Because of industrial action taking place by members of the National Union of Journalists at the Guardian and Observer this week, you may notice some disruption to the availability of new episodes in your Guardian podcast feeds in the coming days. All the work on this episode was done before the strike action began. Help support our independent journalism at theguardian.com/infocus