Nearly a year later, however, Jabhat al Nusra, which U.S. officials believe has links to al Qaida, has become essential
to the frontline operations of the rebels fighting to topple Assad. Not only does the group still conduct suicide bombings that have killed hundreds, but they’ve proved to be critical
to the rebels’ military advance. In battle after battle across the country, Nusra and similar groups do the heaviest frontline fighting. Groups who call themselves the Free Syrian Army and report to military councils led by defected Syrian army officers move into the captured territory afterward.
Among Nusra fighters are many Syrians who say they fought with al Qaida in Iraq, which waged a bloody and violent campaign against the U.S. presence in that country and is still blamed for suicide and car bombings that have killed hundreds of Iraqis since the U.S. troops left a year ago.