Largely peaceful protests in Syria have turned increasingly violent as army defectors fight back against government troops in what some analysts worry could be the beginnings of a sectarian civil war. Forces loyal to President Bashar al-Assad on Tuesday tried to take back a central town from opposition troops. Details of the attack remain scant. Few experts rate the opposition’s chances of Libya-style revolt very highly. Many, however, worry that sectarian violence could spread, possibly even beyond Syria’s borders.