There's a huge wild card that could cripple Obama's plans to defeat ISIS in Iraq

At least 80 people were killed in Baghdad on Wednesday in the worst wave of Islamic State-linked suicide bombings to hit the Iraqi capital yet this year.

Further north, meanwhile, Kurdish Peshmerga forces and the Iraqi army are trying to figure out how they can recapture Mosul - Iraq's second largest city - from ISIS, without getting in each other's way.

For many, the tension is symbolic of the extent to which Iraq has been irrevocably fractured politically and ethnically. And it represents what will ultimately be the biggest challenges in recapturing Mosul: deciding who will lead the offensive and what will happen after ISIS is driven out.

But a huge wild card remains in any plan to retake the city: the role that will be played by Iraq's Popular Mobilization forces (Hashid Shaabi), a group of predominantly Shiite militias that has contributed to, rather than eased, the kind of sectarian tensions that made Mosul susceptible to an ISIS takeover in the first place.

"Sunnis see ISIS as their protection - their wall against Shia revenge," a US official told The Daily Beast's Nancy Youssef on Thursday.

Warzer Jaff is a photojournalist from Sulaymaniyah in Kurdistan who has been embedded with the Iraqi army and, most recently, with Iraq's Special Forces. He told Business Insider that Mosul can't be recaptured before the Sunnis are promised that they will have a part in it - and have something afterward.

"The difficulties in liberating Mosul have as much to do with politics as with military strategy," Jaff said.

That's why a predominantly Sunni unit within Iraq's much more capable special forces will need to drive the offensive, Jaff noted, while the Peshmerga and Shiite militias remain well in the background.

If the Shiite militias have any part in retaking the city itself, "it will be a bloodbath," he added.

'There is no such thing as Iraq any more'

In February, Iraqi Prime Minister Haider al-Abadi announced that the militias would join in the operation to retake Mosul. During a visit to Al-Sadr Teaching Hospital in Basra one month later, Steve Walker, the US consul general there, said the administration would not try to veto Abadi's decision.

"The Obama administration is wed to its current policy, which is much more about messaging than about forging actual victories," Ali Khedery, the longest continuously serving US official in Iraq, told Business Insider on Wednesday.

That messaging often does not correspond to realities on the ground, where Sunnis, Shiites, and Kurds have become more worried about self-preservation than the preservation of a unified Iraqi state. In April, 22 fighters were killed in clashes between the Peshmerga and Shiite militia members in the northern Iraqi city of Tuz Khurmatu.

"Whoever says there is still an Iraqi state - ask them if they can drive through Kurdistan to Mosul and on to Baghdad," Jaff said. "There are borders. The Iraqi government doesn't even control Baghdad."

Capt Shawqat, a Kurdish Peshmerga captain, put it bluntly.

"There is no such thing as Iraq any more," he told The Guardian's Martin Chulov. "There never was, but now it is clear to everyone. Even to the Americans up in the hills."

If it is clear to the American advisers embedded with Iraqi forces, however, it does not seem clear to the administration that sent them there.

President Barack Obama has said repeatedly that he intends to "tighten the noose" around ISIS by training and supporting the Iraqi army. A US defense official told Voice of America last month that "Mosul is the end game in Iraq." And eight Apache attack helicopters were deployed to Iraqi security forces in March.

But few believe that will be enough to halt ISIS' momentum in the country, which continues to be driven in large part by Baghdad's political instability and the perception that Abadi is beholden to Iran.

"Abadi was and is a weak compromise candidate heavily influenced by Iran and its proxies," Michael Pregent, a former embedded adviser with a Peshmerga battalion operating in Mosul and former US Defense Department adviser, told Business Insider earlier this month.

That is largely because of the financial support Abadi's Dawa Party continues to receive from Tehran, Pregent said, despite some of its policy differences with the Islamic Republic.

"The US has no leverage in Baghdad, which has long since been ceded to Tehran," Pregent said.

Khedery - who served as a special assistant to five US ambassadors and as a senior adviser to three heads of US Central Command - agreed that there isn't much under Abadi's control, and that a radical new formula will be needed to defeat ISIS in a society that is so deeply polarized.

"You need another tribal awakening that will allow moderate Sunni Arabs to retake their own areas," Khedery said. "And you need to promise them a stake in their own future. Otherwise, this will never end."

In Iraq, 'things often take longer than expected'

Still, some analysts think the role of Iraq's sectarian tensions in hindering a potential victory over ISIS has been overstated.

"The push to retake Mosul would only be delayed because the Iraqi army is not ready yet," Wladimir van Wilgenburg, a Kurdish affairs analyst and freelance journalist who has been on Mosul's front lines, told Business Insider on Wednesday. "Not because of sectarian tensions."

As one defense official explained to The Daily Beast's Nancy Youssef, "they [the Iraqis] don't have the forces right now. It's not going to happen. They cannot sustain it."

Michael Knights, an expert on Iraq at the Washington Institute, said he'd anticipated delays.

"People who know Iraq know that things often take longer than expected," Knights told Business Insider last week. "But those people should also admit that sometimes they happen shockingly fast - so we all need to be ready for a lurch forward by the coalition and/or some kind of implosion of ISIL control."

The Iraqis have slowly been retaking territory around Mosul and are now positioned 50 miles south and 20 miles north of the city.

"My assessment would be that we'll have Mosul surrounded by year-end," Knights said.

Maj. Gen. Gary J. Volesky, a commander of the US anti-ISIS operation in Iraq, told reporters in a Wednesday press briefing from Baghdad that Iraqi forces are putting "more and more pressure" on ISIS around Mosul.

"We get indications of their challenge to resupply their forces, move in men, weapons and equipment throughout Iraq," Volesky said. "We get indications that every time they hear an aircraft or one of our platforms, they go to ground. They don't want to move because they know they're about to get struck."

The role of Hashid Shaabi in retaking the city was not mentioned during the press conference. When asked directly if he thought Mosul would fall by the end of this year, Volesky said only that the US is "supporting their [the Iraqis'] plan to get to Mosul and defeat Daesh." (Daesh is an alternate name for ISIS.)

Peshmerga captain Lt. Col. Srud Barzinji, for his part, told The Guardian's Chulov that he doesn't expect a meaningful push for Mosul to happen by the end of this year. The US Director of National Intelligence, James Clapper, evidently doesn't expect it to, either.

"We will retake Mosul, but it will take a long time and be very messy," Clapper told The Washington Post. "I don't see that happening in this administration."