Ever since ISIS captured Mosul in June 2014, political and military leaders in Iraq and the United States have regarded the liberation of Iraq’s second-largest city as a sine qua non for rolling back the caliphate. The campaign against ISIS has made progress on many fronts, but predictions that the army of terror would soon be dislodged from Mosul appear premature at best.

The primary reason why the assault on Mosul has been repeatedly postponed rests with Iraq’s feeble and fractured central government. Recently, demonstrators loyal to radical Shia cleric Muqtada al-Sadr raucously occupied the parliament in Baghdad. As lawmakers fled the scene, the demonstrators – chanting “you are all thieves” – called for the dissolution of the government. Prime Minister Haider al-Abadi ordered the arrest of the protesters and declared a state of emergency, but the latest crisis reveals the intensifying power struggle within the political system. In the recent past, such instability has nurtured the jihadist threat.

Under Abadi’s predecessor, political dysfunction in Baghdad set the conditions for the rise of ISIS. Iraq’s central government had welcomed Iranian assistance because of its fear of abandonment by America, and this hardened the Shiite character of the regime. Nouri al-Maliki’s tenure was marked by relentless marginalization of the Sunni minority. First, the Sons of Iraq – the force that with the U.S. had vanquished ISIS’s forerunner, al-Qaeda in Iraq – were disbanded and harassed. The Iraqi army was gradually transformed into a de facto Shia militia. Sunni opposition politicians - including the deputy prime minister - were arrested, and elections were manipulated.

The Shia-dominated government’s chronic misrule now represents the greatest threat to Iraq, according to Emma Sky, a former advisor to the Coalition Provisional Authority. Sky observes that the destructive politics of the “green zone” – the walled-off enclave on the Tigris river where Iraq’s political class divvy up state largesse, generally for themselves and their clients – has put in jeopardy Iraq’s entire post-Saddam order. It has alienated crucial constituencies, not least the Sunni and Kurdish minorities whose support is crucial to the liberation of Mosul.

While stationed en masse in Iraq, the U.S. army was dubbed “the defense militia for those [Iraqis] without a militia.” Today, Sky writes, “the sad reality is that Iraq has become ungovernable, more a state of militias than a state of institutions.”

Whatever its costs, the robust U.S. presence in Iraq – political as much as military – ensured a degree of Iraqi social and political cohesion that prevented the consolidation of power in Baghdad under one sect at the expense of others. It is precisely this tyranny of the majority that arose in the wake of America’s withdrawal, and that ISIS has exploited to its advantage among the aggrieved and alienated Sunni minority ever since. Unfortunately for ISIS’s enemies, this state of affairs shows no signs of abating.