In June last year the world's attention became fixed on the progress of so-called Islamic State, or IS. They had just captured Mosul, Iraq's second-largest city. Since then a reported 20,000 fighters from all over the world have joined them. They have killed and enslaved thousands. They have captured towns, oil fields and dams. They control vast swathes of Iraq and Syria. IS are more brutal, sophisticated and enduring than anyone could have predicted. We test the argument that stopping IS will ultimately mean talking to them.

(Photo: ISIS Propaganda image)