Some analysts said during the Second Gulf War that al Qaeda would be trading up from Afghanistan if it secured a base in Iraq. It was a prescient thought, but perhaps premature: between 2007 and 2010, Iraqis by and large rejected that fate for their country and dealt a body blow to the foreign Sunni jihadists who entered the country. But then the Syrian Civil War began. Non-Syrian jihadists entered Syria in numbers - though so too did foreign brigades sponsored by Iran and Hezbollah - and many of the Sunnis among these fighters came from nearby Iraq to fight in solidarity. Ironically, some had once been agents of Syrian state-sponsored terrorism. The most significant of these "new" groups has been the Islamic State of Iraq and the Levant (ISIS), which over the past year has spent as much time fighting other Syrian rebels groups as the Syrian Arab Republic's forces. ISIS was once aligned with al Qaeda's central command, but has since gone its own way. Though increasingly a multinational conglomeration after absorbing many of the Nusra Front's foreign fighters, it has only one strategic goal today: that of gathering all Sunnis living in "Greater Syria" under its rule.

"Many [ISIS fighters] have come from Afghanistan and Iraq," says Syrian activist Abu Ibrahim Ar-Raqqawi, describing their rule in his country's northern reaches as an effort to build a state, "cleanse" it (especially of rival anti-Assad actors), and only then begin the fighting against Assad in earnest. "Our Syrian fighters are farmers and masons, they don't have that experience." Indeed, and ISIS has delivered on what Abu Musab al-Zarqawi could not. It has set down foundations for an emirate in the Sunni heartland abutting Turkey, Iraq, Syria, and the Caucasus Mountains. ISIS is not al Qaeda. And because of this difference in priorities, it has done what al Qaeda failed to do: secure, as Aymenn Al-Tamimi tweeted, "contiguous territory, [a] series of linked strongholds, [and] provision of services." For much more than mere shakedowns of rich merchants and handing out candy to children is planned for northern Iraq in the coming weeks.

Just days ago, ISIS pushed forward from its safehouses and camps in the Nineveh Governorate, which it had won control over in the past months, to take over the city of Mosul. It has attacked several other cities in northern Iraq as well, and disrupted the siege that federal forces in Iraq brought against it and its allies in Al Anbar Governorate this Spring. Mosul was living under a state of siege with the government resorting to an air bridge due to the danger ISIS ambushes posed to highway traffic. The group has for over a year now been following a strategic campaign it dubbed "Soldier's Harvest": the aim has been to retake the territories lost by al Qaeda-aligned jihadists during the final years of the U.S. Occupation by terrorizing the local authorities into quitting the fight. ISIS would then fill the resulting vacuum caused by their retreat. "This started in rural sections of Iraq such as the desert regions of Anbar and the Hamrin Mountains that stretch across Diyala and Salahaddin [Saladin]," wrote Iraq watcher Joel Wing, and "now ISIS is moving into urban areas."

Its other effort - "Breaking the Walls," so termed because it involved freeing captured Sunni militants from Prime Minister Nour al-Maliki's jails - is also doing well in Mosul, with over 1,000 detainees freed this week after their guards fled. With Mosul mostly secured - its banks and military depots have been emptied by the jihadists for redistribution to its forces in Iraq and Syria - and tens of thousands now jamming the roads out of the region, ISIS is simultaneously staging offensives into the nearby Saladin Governorate and points further south, heading towards the capital. There has as yet been no significant armed government response to the crisis in Nineveh, a province that is also home to many of Iraq's remaining Assyrians and other Christian minorities. In Syria, ISIS has closed down churches to set up indoctrination centers (Da'wah) for youth: darker charges of kidnapping and execution have followed.

Disillusionment with Maliki's sectarian agenda, power-grabs, and refusal to reign in the abuses of federal forces has been coupled with a worsening economic situation in the area as ISIS and its sometimes-allied fellow insurgents milked Iraq's second largest city for all it was worth: Iraq is, after all, the treasury of several Islamist militias fighting in Syria thanks to smuggling, Islamic charities, and plain old-fashioned extortion, theft, or ransom demands. Local media reported that, trusting less in the Iraqi Army than in protection money, Mosul's well-to-do chose to pay ISIS not to attack over paying the security services to defend. Unfortunately for them, ISIS's Mosul organization was not the Italian 'Ndrangheta. The local governor, Adheel al-Nujaifi, did not acknowledge such unpleasant details in his post-loss tirade against the security forces. But mass desertion and retreat was the result of this ill-advised trade off: the roads out of the city are littered with discarded army and police uniforms.

The Mosul area is home to Kurdish peshmerga now gearing up to fight ISIS where the security services have not. Despite an announcement from ISIS that it has no beef with the Kurds, clashes have been reported and the road to Kirkuk is in ISIS's hands. The Kurds are not fighting for Maliki's sake, though, but for their own autonomous region. Militarily, the federal government may only really be able to rely on the U.S.-trained Special Operations brigades - which did force ISIS to retreat from the city of Samarra, hometown of ISIS's leader Abu Bakr al-Baghdadi, with heavy losses - air force, and a handful of regular army divisions.

None of these well-trained and politically reliable units were on hand in Mosul this week, though, and a large chunk of the Iraqi military is tied up in Al Anbar in a reprisal campaign against anti-government militias that took over the major towns there earlier in 2014. Shortages plague the regular army, and the national police have little stomach for enduring the constant assaults on their stations. The city effectively fell overnight: the main government offices, the northern dams supplying power and water to central Iraq, the airport, and the oil fields are all in ISIS's hands now. Watching the loss - and the militants parading around in captured Humvees - must be especially galling for the U.S. military because the 101st Airborne Division's initial occupation of Mosul a decade ago was hailed as an exception to the rule of anarchy in the rest of the country. Mosul was actually a "model" for the Surge and the "Awakening" that followed the worst of the internal violence in Iraq under the U.S. Occupation (2003-2011), especially in Fallujah, to the southwest.

For its part, Fallujah - site of two bloody battles after 2005 - has been outside of Baghdad's control for some months. Not that it was ever fully under federal or even U.S. authority during the Surge. Though ISIS is present, the city's loss is far more the result of the "Awakening's" politics being well past their sell date in the region. The Sunni Arab "Sons of Iraq" tribal movement could have been a significant moment in Iraqi state building there. But it was ultimately compromised by the inability of Maliki's government to accept the legitimacy of the movement. Prior to the Sons' formation, the incessant attacks on Sunni communities by Shia militias and terrorists meant that many Sunnis decided not to trust the new authorities: as Phil Williams wrote in 2009, "the very force that was designed to protect them [the Iraqi national police] preyed on them instead, engaging in sectarian killings, extortion, robberies, and kidnapping." In response to this, and the depredations of al Qaeda, Iraqi Sunnis began organizing themselves into self-defense leagues and soliciting U.S. assistance (mainly in the form of air support and monies that Iraqi officials either did not have or were hoarding). Eventually, these militias were turned on the nebulous "al Qaeda in Iraq" jihadists, men who were led by foreigners and had displayed again and again a complete inability to govern the Sunni areas they took over. By 2011, when the U.S. left the county, most Iraqis had turned on this bandit coalition and (with sufficient U.S. "inducement") many influential tribal leaders put their men on the barricades to repulse the terrorists, rather than ordering them to mortar checkpoints alongside them.

When Sunni leaders went to Baghdad cap in hand to obtain official blessing for their militias during the Surge, the Maliki government very reluctantly granted it, and then stalled on implementing the understandings that had been reached. This was due to the Shia leaders' fears of arming groups that only weeks before had been fighting in the anti-government camp, something that the U.S. did not seem to grasp on its way out of Iraq. This federal recalcitrance, in turn, convinced some of the Sons of Iraq that they were better off keeping their arms and rejecting vague promises of official recognition and salaries. And after the contested 2010 elections that returned Maliki to power - before the U.S. even left the country, it is worth noting - Al Anbar found itself heading back to where it was before the "Awakening" began.

The catalyst for the (third?) Battle of Fallujah in January 2014, though, was not spillover from Syria but a disastrous raid on a Sunni protest camp by federal forces. The two "Arab Spring-style" protest camps set up in that city and nearby Ramadi were set upon by the federal authorities; Sunni clerics began calling for open revolt against Baghdad to defend the protestors. ISIS took advantage of the chaos to organize in the city, yet the initial revolt - and the people the government and local sheiks have been trying to talk down from the barricades - was staged by fed-up local militias who had formally been the guarantors of a cold peace. Maliki's deputy PM Saleh al-Mutlaq contends that the typical heavy-handed response of Baghdad to an assassination in the province - unrelated to the demonstrations - killed the cold peace that had been maintained by the "Sons of Iraq."

Sunni grievances against the government are real and legion: job discrimination, undue prosecution of activists, human rights violations by the police, welfare cuts that "punish" the Sunnis for their collaborationist role in past dictatorships. Well before this uprising, "the Sunnis [had] lost faith in the political process and the jihadists were once again able to make inroads among them." Hence the castle-building Iraqi political factions all continue to engage in, because it is one death squad or another if you try to play honestly by constitutional rules the Maliki government itself doesn't respect. "State collapse produces sectarianism - not the other way around," as James Fromson at the Middle East Institute writes. ISIS and the federal government agree on one thing implicitly: there is an Iraqi nation, but there is only a weak state grafted onto it, and representatives of different factions should seek to capture it for their own in-group. This mistrust, and not the Syrian Civil War alone, ultimately collapsed the uneasy power-sharing arrangements the "Awakening" had brokered between local (predominantly Sunni) and provincial authorities. Sunnis are also angered by Maliki's alliance with Iran, which in practical terms allows the IRGC to fly men, material, and money over the country into Lebanon or into Syria to back Assad.

Iraq's Shia leadership, on the other hand, generally accepted such crackdowns on the Sunni community leaders because they saw the virulent rhetoric aimed at them by some Sunni politicians or media personalities (notably Al Jazeera's Arabic service, now banned in Iraq), rhetoric which evoked the worst promises Saddam Hussein and al-Zarqawi made to destroy them. The Shia see their association with Iran as necessary to counter Saudi and Gulf influence among Sunni insurgents. Yet Sunni politicians like the Mosul governor, says Kirk. H. Sowell of the Uticensis Risk consultancy, have been "feckless": Sowell notes that he and army command in Mosul spent more time fighting each other than ISIS or other anti-government groups such as the (pro-ISIS) General Military Council and Naqshbandi Army or (anti-ISIS) Jamaat Ansar al-Islam. Such incitement and infighting, and the ongoing car bombings and shootings carried out by antigovernment terrorists, was taken as cause enough to disregard Sunni complaints about Shia heavy-handedness. So, in Fallujah, ISIS was able to set up a sphere of influence - but one it has had to share with local groups, including many who are uninterested in grand Levantine designs, but instead want more local autonomy.

In Mosul, it seems ISIS has the stage more to itself, the work of diligent base-building in the previous months. Al-Tamimi notes that in the north, ISIS dominated the military effort (its casualty figures suggest as much as well) and gained the most ground and material, unlike in Fallujah. Surely, then, ISIS will consider power-sharing arrangements in Mosul only by promising unity now and later entrenching itself at the expense of its so-called "friends," many of whom - like the Free Syrian Army - realize too late why the armory doors are now locked and guarded against them. As Ar-Raqqaqi chillingly notes of his experience with them in Syria, "ISIS found its place by dismantling the rebels there one by one." This will be their immediate aim, as it has been in Fallujah, even before they finishing mopping up what is left of the security services in the north.