An Iraqi flag now flutters over government buildings in the city of Ramadi. After seven months in the hands of the Islamic State, Iraqi troops once again control the city.

But unless the Iraqi government is prepared to make some dramatic changes, the victory will be fleeting. Iraq’s religious and ethnic divides foster instability and create fertile grounds for Islamic State resurgence. Impending decisions by the government—should it seriously wish to destroy the Islamic State—could significantly reshape Iraq’s geopolitical climate in 2016.

One way or another, if the Islamic State is to be eradicated from the nation, the Iraqi government must be prepared to relinquish some power. To drive the Islamic State out, the government must gain the help of the Sunni populace or find some way to replace it.

The Sunni Necessity

Sunnis make up less than 40 percent of the demographic in Iraq. But despite being a minority, they are key players in the war on the Islamic State.

Consider what happened back in June 2014. The predominantly Sunni city of Mosul fell to the terrorists. But as Islamic State terrorists waltzed into Iraq’s second-largest city, they were met with barely any resistance. The population of the city had grown tired of Iraqi Prime Minister Nouri al-Maliki and his pro-Shiite policies. For years the pro-Iranian prime minister had been shunning and ostracizing the Sunni minority across the country.

There is little wonder then that the Sunnis in Mosul didn’t bat an eye as the Iraqi forces were driven over the Tigris River and back to Baghdad.

In an article titled “Bombs Can’t Defeat ISIS, but Iraq’s Sunnis Can” the Independent pointed to the Islamic State gaining strength “from an established web of interpersonal and inter-organizational links.” That web is woven through the Sunni populace.

Islamic State: A Political Partner

That isn’t to say that all Sunnis are cut from an identical ideological cloth as the Islamic State. Not all Sunnis who support the Islamic State do so because of its conduct. In the New York Times bestseller ISIS: Inside the Army of Terror, coauthors Michael Weiss and Hassan Hassan explain how some Sunnis are motivated by politics more than religion.

Many Sunnis consider themselves hard done by. First they lost power in Iraq when Sunni leader Saddam Hussein was overthrown and Maliki—a Shiite—was installed by the United States. His pro-Shiite, pro-Iranian policies led to deep sectarian rifts and violence.

Jumping forward to today, Iran has troops stationed in Iraq, it has heavy sway in Iraq’s political sphere, and it enjoys burgeoning popularity among Iraq’s Shiite communities.

Further enraging Sunnis, reports of Qassem Suleimani and his heavy-handed brigades are becoming widespread. Sunnis are suffering more and more as Shiite forces “liberate” towns from the Islamic State. The militias take the Sunni population from one subjugation to another.

Over the border in Syria, more atrocities are carried out on Sunnis by Shiite leader Bashar Assad and his pro-Shiite allies.

With little leadership shown by neighboring Sunni nations and the U.S., the Sunnis in Iraq are left with very few options when it comes to countering Iranian hegemony and the surging power of Shia Islam in the Middle East.

As Weiss and Hassan state, “They [the Sunnis] view the struggle in the Middle East as one between Sunnis and an Iranian-led coalition, and they justify ultraviolence as a necessary tool to counterbalance or deter Shia hegemony.”

A Rift Too Wide

When you look at the damage to Sunni-Shiite relations in Iraq, coercing the Sunnis to support Shiite military action in northern Iraq looks improbable. The Shiite government might want to bring the Sunnis on board, but the chasm in relations has been edging larger and larger with every allegation of bias decisions against Sunnis over the last decade.

Creating a remedy for the Sunni population’s many grievances could prove exceedingly difficult, if not impossible. It would mean acquiescing on demands for more Sunni power in the government. This alone would be a bitter pill to swallow for most Iraqi government officials.

Iran wouldn’t look too kindly on handing more power to the Sunnis either. While current Iraqi Prime Minister Haider al-Abadi doesn’t appear as deep in Iran’s pocket as his predecessor Maliki was, Iran’s sway over the nation cannot be ignored. Abadi owes a great debt to Iran. Tehran has led, funded and trained the Shia militias that now guard the roads to Baghdad. Without them, the Islamic State might well have pushed to the gates of the capital.

Iran doesn’t want to see Iraq fall to the Islamic State. But neither does it want to see years of work infiltrating and manipulating the government undermined if the Iraqi government tries to appease the Sunnis.

Nobody wants to lose power. It is as simple as that. After the recapture of Ramadi, Abadi may decide that victory is achievable without the support of local Sunnis—thereby avoiding the need to kowtow to the Sunnis. This may signal a far more dangerous turn in Iraq for 2016.

If Abadi doesn’t try to gain Sunni support, the sectarian rift may widen further. And there is still the matter of the Islamic State to be dealt with. Without the Sunnis, Abadi must look elsewhere for help.

And who is offering air and ground support, training, armaments and funding? Iran.

Tehran has already been given far more leeway in Iraq than ever should have been allowed. With both Fallujah and Mosul being larger, more densely populated, and better defended than Ramadi, Iraq will be in need of more troops, more tanks, more air cover.

Without the aid of the general population, Abadi will need to use force of arms to keep the Islamic State from returning. Right now Iran looks to be the only likely source.

Keep watching, because the Iraqi government will play a dangerous game in 2016. If it refuses to cooperate with the Sunni population and gain its aid in the fight against the Islamic State, then the government will need to forfeit more sovereignty to a military force willing to step in and help. Iran is ready and waiting.