Iraqi forces are "ahead of schedule", the Pentagon has said, as they begin the second day of the battle to retake Mosul from so-called Islamic State. <br/><br/>But spokesman Peter Cook warned that the campaign could take some time as it remained to be seen whether the jihadist group would stand and fight. <br/><br/> Fighting continued overnight, with IS militants attacking Iraqi army tanks. An army unit says the southern frontline is still some 40 kilometre from the city. <br/><br/>IS militants overran Mosul in June 2014, before taking control of much of northern and western Iraq. <br/><br/>According to Mr Cook, their leader, Abu Bakr al-Baghdadi, chose a mosque in the city as the place to proclaim the establishment of a caliphate, so retaking the city would be symbolic.<br/><br/>A coalition of about 30,000 Iraqi security personnel, Kurdish fighters, Sunni Arab tribesmen, and Shia paramilitary forces began their advance on the jihadists' last major urban stronghold in the country yesterday.<br/><br/>The Kurds seized several villages in the first few hours of the operation, and announced yesterday evening they had achieved all their key objectives, including recapturing 200 sq km and nine villages in under 24 hours. <br/><br/>They also secured an additional significant stretch of the road from the Kurdish city of Irbil to Mosul.