“To those of you who were intrigued by the ISIS ideology,” said one of the leaflets, using the group’s acronym. “This is your last opportunity to quit your work with ISIS and to leave those foreigners who are in your homeland. Stay at home, raising the white flags as the forces approach.”

On state-run television, Prime Minister Haider al-Abadi of Iraq announced the beginning of the offensive, describing it as “a new dawn” and calling on his troops “to move bravely forward to liberate what is left of the city.”

The assault is taking place amid new concerns about the condition of hundreds of thousands of civilians still trapped in the western part of the city. Food, water and cooking fuel have all been reported to be in short supply, and residents have described increased harassment from Islamic State fighters preparing for the attack…

The fight for Mosul’s western half could be even more protracted than for its east. The west is home to neighborhoods of narrow streets, some so small that it will not be possible for Iraqi troops to enter them in their fortified Humvees. That may make the Islamic State’s signature suicide bomb attacks even more effective.