KHAZER, Iraq — The long-awaited offensive to retake Mosul from the Islamic State group began Monday with a volley of U.S.-led coalition air strikes and heavy artillery bombardments on a cluster of villages along the edge of Iraq’s historic Nineveh plain east of the militant-held city. Iraq’s Kurdish peshmerga fighters led the initial assault, advancing slowly across open fields littered with booby-trapped explosives as plumes of black and orange smoke rose overhead — the opening phase of an unprecedented campaign expected to take weeks if not months, and involve more than 25,000 troops. Aid groups have warned of a mass exodus of civilians that could overwhelm refugee camps. After a string of victories by Iraqi ground forces over the past year, the extremists now control less than half the territory they once held, and Iraqi Prime Minister Haider al-Abadi has pledged the fight for Mosul will lead to the liberation of all Iraqi territory from the militants this year.
