Sunni rebels are preparing to make a major assault on the capital city of Baghdad with the help of thousands of sleeper cells inside the city already who only await the go code to be unleashed.

The scenes in Baghdad are reminiscent of the worst of the sectarian bloodletting that occurred in 2006-07. Then, as now, Shia militias are roaming the streets, picking up Sunnis who are then never heard from again. The number of those who disappear is climbing while government security forces conduct massive sweeps in the city in order to foil the sleeper cells.

Reuters:

Iraqis speak of a "Zero Hour" as the moment a previously-prepared attack plan would start to unfold.

A high-level Iraqi security official estimated there were 1,500 sleeper cell members hibernating in western Baghdad and a further 1,000 in areas on the outskirts of the capital.

He said their goal was to penetrate the U.S.-made "Green Zone" - a fortified enclave of government buildings on the west bank of the Tigris - as a propaganda victory and then carve out enclaves in west Baghdad and in outlying areas.

“There are so many sleeper cells in Baghdad,” the official said. “They will seize an area and won’t let anyone take it back... In western Baghdad, they are ready and prepared.”

A man who describes himself as a member of one such cell, originally from Anbar province, the mainly Sunni Western area that has been a heartland of the insurgency, said he has been working in Baghdad as a laborer while secretly coordinating intelligence for his group of Sunni fighters.

The attack on the capital will come soon, said the man, who asked to be called Abu Ahmed.

“We are ready. It can come any minute,” he told Reuters during a meeting in a public place, glancing nervously around to see if anyone was watching.

“We will have some surprises,” he said. He pulled his baseball cap down tight on his face and stopped speaking anytime a stranger approached.

A portly man in his mid-30s wearing a striped sports shirt, the man said he fought as part of an insurgent group called the 1920 Revolution Brigades during the U.S. occupation and was jailed by the Iraqi government from 2007-2009.

He gave up fighting in 2010, tired from war and relatively optimistic about the future. But last year, he took up arms again out of anger at a crackdown against Sunni protesters by the Shi'ite-led government, joining the Military Council, a loose federation of Sunni armed groups and tribal fighters that has since emerged as a full-fledged insurgent umbrella group.

While it was not possible to verify all details of his story, Reuters reporters are confident of his identity.

Those enclaves that will be carved out will act as buffer zones between Shia forces and the caliphate. It is doubtful that the Sunnis can take the entire city. But they can certainly establish strong points and dare the Iraqi army to try and dislodge them. As the Syrian army discovered in Aleppo, the rebels make good use of innocent civilians, using them as human shields. It remains to be seen if the Iraqi government will be as pitiless as President Assad in going after rebels hiding behind civilians.

It appears that a major battle is about to erupt in a city of 7 million. It's hard to see how massive bloodshed can be avoided.