Battered and in retreat over much of northern Iraq, Islamic State has launched a surprise counterattack far from its last redoubt of Mosul, taking over three districts of Kirkuk, killing dozens and holding perhaps hundreds hostage. Friday’s pre-dawn assault on the northern oil city, which is contested byArabs and Kurds, was designed to show the terrorist group’s enemies that it was still able to launch spectacular assaults at will and that it remained far from defeated despite a five-day push to oust it from Iraq’s second city and nearby areas that it seized two years ago. Kurdish forces rushed to Kirkuk to defend the city and, in doing so, at least partly fulfilled another of the group’s goals: relieving pressure on it in the main battlefield, where Iraqi and peshmerga forces continue to face intense resistance as they grind towards Mosul.