The posters of President Bashar al-Assad once hung proud in Syria’s capital. Supporters of the regime would confidently predict the defeat of the “terrorists” - the accepted term for the rebel opposition. In the last few weeks, however, the the insurgents have turned the tide of the civil war by winning a string of battlefield victories against Mr Assad’s forces. In the north, a newly unified rebel coalition called the “Army of Conquest” managed to capture Idlib, a provincial capital, and much of the surrounding territory.