MOSUL, Iraq - Perched atop a mound of rubble, Abdelsattar al-Hibbu surveyed what remained of his second-floor office: twisted iron and centuries-old stone reduced to dust by an airstrike.

Extremists have overrun Iraq’s northern city of Mosul, highlighting the weaknesses of government security forces. CNN looks at how things got to this point.

When Islamic State fighters swept through Iraq and Syria, their biggest prize was Mosul, a city of 1.2 million that is Iraq's second-biggest. In weeks, the fight to retake it will likely commence.

It captured Mosul in June 2014, butchered thousands of people and prompted an exodus from Iraq’s second largest city. Harrowing accounts of suffering and survival surfaced in the ensuing months.

A long-awaited offensive to recapture the Iraqi city of Mosul from the Islamic State began early Monday morning, with U.S. forces involved in their largest operation since withdrawing from the ...

Today, we are facing another massive military operation (the fall of Mosul and the final "defeat" of ISIS in Iraq), and once again we do not yet have a Phase IV plan.

The following is a script from “The Battle for Mosul,” which aired on Nov. 6, 2016. Lara Logan is the correspondent. Max McClellan and Richard Butler, producers.

Mosul is perhaps the group’s last major stronghold in Iraq. A Looming Humanitarian Crisis As many as 1.2 million people could be displaced by the fighting in Mosul, according to the United Nations.

MOSUL, Iraq-- Between 9,000 and 11,000 people were killed in the nine-month battle to liberate the Iraqi city of Mosul from Islamic State of Iraq and Syria (ISIS) militants -- a civilian casualty ...

Omar Turki defied Islamic State and fled the city of Mosul on foot last month with his family of five, the youngest just 6 months old. The battle for Mosul: How to free 1 million residents without ...