engel. reporter: isis today hit back with a sneak attack on a government complex in the city of kierkuk where they exchanged fire with security forces. isis may be trying to slow down the assault on mosul. it doesn t seem to be working. iraqi troops say they pushed within just four miles of the city. the isis capital in iraq. the biggest battle was for control of the town of bartella on mosul s eastern doorstep. to reach the front, we climbed into an iraqi special forces old american humvee shot and nearly blown up by isis bomb. iraqi troops brought in the heaviest weapons. isis fought back with suicide bombers. but all this was music to the iraqi soldiers ears. we ll win, god willing. be in mosul in days. isis does seem to be retreating from some of its positions.