So the liberation of Mosul won't happen soon, certainly not in 2016. Meantime, it is possible to imagine how Raqqa could fall much sooner, with a cataclysmic impact on ISIS. That's because Raqqa is the theological capital of the caliphate, where its leadership is based, along with the bulk of foreign fighters; its demise would deal a crippling blow to the ISIS story line of building a transnational Islamic state.