This article is from the archive of our partner .

Iraq is on very precarious footing after Islamic militants essentially rolled over the city of Mosul today, driving out security forces and causing 150,000 residents to flee.

The capper to a 48-hour assault on the city by the group the Islamic State of Iraq and the Levant (known, confusingly, as both ISIS and ISIL) is sending shockwaves through the region. Iraqi Prime Minister Nouri al-Maliki declared a national "state of emergency" and the U.S. State Department weighed in, calling the situation "extremely serious."

This development, an emblem of the deterioration of the security situation in Iraq, is particularly noteworthy because it was hardly expected to happen in Mosul. As Foreign Policy noted:

Earlier this year, ISIS seized control of the restive city of Fallujah, but their conquest of Mosul represents something very different. Fallujah had long been a hotbed of the anti-American insurgency and a homebase for large numbers of Islamist militants. U.S. forces, even at the peak of their powers, had trouble holding the city. Mosul, by contrast, has never been seen as a militant hotbed. In earlier years of the war, Iraqis even visited the city for vacation."

For some perspective:

This rout of police stations, government buildings, and other security installations will bring new focus on ISIS, a group that was linked to al-Qaeda until earlier this year when the groups officially split after a long power struggle. 

By evening, there were reports that group, now armed with American-made weapons and humvees that had belonged to Iraqi forces, is continuing on north to Kirkuk. 

This article is from the archive of our partner The Wire.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.