On the first day of what could be a long campaign to liberate Mosul from the grip of the Islamic State, Iraqi forces are on track to achieve their military objectives, and the offensive is going according to plan, the Pentagon said Monday.

“We are in the first day of a difficult campaign that could take some time,” said Peter Cook, a Pentagon spokesman, adding, “Early indications are that Iraqi forces have met their objectives so far and that they are ahead of schedule for this first day.”