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Jabhat al-Nusra does count Syrian veterans of the Iraq war among its numbers, men who bring expertise — especially the manufacture of improvised explosive devices (IEDs) — to the front in Syria. Still, Jabhat al-Nusra is not the only rebel outfit to use IEDs and other groups — some so-called moderates operating under the loose umbrella of the Free Syrian Army (FSA) have also allegedly used suicide bombers who were either willing or unwilling (i.e prisoners). Like Jabhat al-Nusra, a number of other Islamist groups also want to install an Islamic state in Syria, while even secular rebel units increasingly speak in ugly sectarian terms that demonize minorities, particularly members of Assad’s Alawite sect. Yet only Jabhat al-Nusra’s tactics were designated as “terrorist” by...