Six months since Iraqi forces launched a vast operation to oust the Islamic State group from second city Mosul, they have recaptured its east and are battling for the west. Here are key dates in offensive: - The battle begins - - October 17: Iraqi forces launch the assault. The jihadists had declared an Islamic "caliphate" there in June 2014 after seizing much of northern and western Iraq. Tens of thousands of army, police and counter-terrorism troops are thrown into the long-awaited offensive with air and ground support from a US-led coalition. Kurdish militias also take part in operations north and east of the city. By late October, the army is within 15 kilometres (10 miles) of Mosul. - Entering Mosul - - November 1: The army says it has entered Mosul city for the first time since 2014. - November 3: IS chief Abu Bakr al-Baghdadi breaks a year-long silence, urging followers to fight to the death for Mosul. The Iraqi advance begins to slow. - November 13: Iraq says it has recaptured Nimrud, an ancient city southeast of Mosul. - November 23: Shiite-dominated paramilitary units known as the Hashed al-Shaabi say they have cut IS supply lines between Mosul and the jihadists' Syrian stronghold Raqa, 400 kilometres (250 miles) to the west. - Change of tactics - - December 29: Government troops end a two-week pause and launch the second part of their assault on east Mosul. - Tigris River bank - - January 8: Iraqi units reach the Tigris River that divides Mosul and take up positions near one of the city's five bridges, all now destroyed. - January 14: Elite Counter-Terrorism Service forces seize Mosul University. - East Mosul taken - - January 18: The head of special forces announces the "liberation" of Mosul's east bank, but sporadic fighting continues for several days. - January 24: The Joint Operations Command coordinating the fight says the east has been "fully liberated". - Battle for west begins - - January 24: As Iraqi forces prepare to attack Mosul's west, the UN warns that 750,000 civilians there are at "extreme risk" and a quarter of a million Iraqis could flee their homes. Western Mosul, home to the densely populated Old City and a traditional jihadist bastion, is expected to offer stiffer resistance than the east. - February 19: Prime Minister Haider al-Abadi announces the start of the campaign for western Mosul, with Iraqi forces backed by coalition air power and increased support from coalition advisers. - February 20: New Pentagon chief James Mattis makes his first visit to Baghdad as Iraqi forces retake Al-Buseif village overlooking the airport and south Mosul. - February 24: Iraqi forces seize full control of Mosul airport and enter their first west Mosul neighbourhood. - February 27: They take control of the fourth bridge over the Tigris, the southernmost of the five bridges partly destroyed by air strikes or IS. - March 7: Government forces take key buildings including the Nineveh province headquarters and Mosul museum. - March 12: More than a third of the city's western side has now been retaken, a top military official says. March 25: Iraqi officials say air strikes in west Mosul killed scores of civilians. The coalition says it bombed an area where civilians were reportedly killed, later saying it "probably" played a role in the civilian casualties. March 28: The UN says more than 300 civilians have been killed since the start of the west Mosul operation. April 11: An Iraqi military spokesman says IS now controls less than seven percent of the country, down from 40 percent in 2014.