Northern Syria — U.S. intelligence has confirmed ISIS was responsible for a an attack at a restaurant in the city of Manbij Wednesday that left four Americans and more than a dozen others dead. Manbij had been considered a relatively safe place. Now, the bombing has underlined how ISIS remains a lethal force with widespread reach.

The attack happened around 150 miles from where U.S. troops and their allies have ISIS pinned down. As far as the terror group is concerned, any street in Syria is the front line.

Even as ISIS is diminished on the battlefield, sleeper cells have increased attacks away from it, morphing from a territorial force to an insurgent terror network, launching hit and run attacks. A drive-by assassination of a Kurdish commander took place in broad daylight along a road miles from any front line.

Ahmed Omar, a political adviser to the Kurdish government, said the decision to withdraw 2,000 U.S. forces from Syria has only emboldened the terror group. ISIS would not be finished — instead, they would just change their strategy and tactics, he said.

While commanders here believe the final push against ISIS may be over in less than two months, no one dares predict what comes after that.