A diverse coalition of Iraqi forces launched a long-awaited offensive against Islamic State in Mosul, one of the last major cities still controlled by the militant group.

In a nationally televised announcement early Monday, Iraq time, Prime Minister Haider al-Abadi announced the start of the push to take back Iraq’s second-largest city.

Reclaiming Mosul is seen as essential to the broader battle against Islamic State. The group has suffered a string of losses lately in its self-declared caliphate, including on Sunday, when Syrian rebels backed by Turkey and the U.S. drove the militants from the Syrian town of Dabiq.