DIBIS, Iraq – The parched hills outside Kirkuk are one of the last front lines against Islamic State in Iraq. Here, Kurdish Peshmerga checked the extremist advance in 2014 and, with the aid of coalition air support, pushed ISIS back to the gates of the city of Hawija. Today, Iraqi security forces, including Iranian-backed Shi’a militias, are assaulting Hawija from the west, while the Kurds hold the line to the east.Yet the aftermath of Monday’s Kurdish independence referendum has now moved the focus to Baghdad’s threats to send armed forces to Kirkuk.The Kirkuk region has been disputed between Kurds and Baghdad for decades. Saddam Hussein tried to depopulate the Kurdish residents from areas around the city. One taxi driver told how his village lay empty until the US-led invasion of 2003, when his family was able to come back. “We saw how the Iraqi Army left Kirkuk to ISIS in 2014 without firing a bullet,” a senior Peshmerga officer told reporters on the eve of the referendum. Now the message from the Peshmerga is that the city is part of the Kurdistan Regional Government and will stay that way.The Iraqi Parliament voted on September 14 to remove Kirkuk Gov. Najmaldin Karim, but he has stayed at his post. Eighty percent of Kirkuk’s residents turned out to vote in the independence referendum. The vote has angered Baghdad, which ordered the airports in the Kurdish region closed. The day after the referendum, the Iraqi Parliament also called on Prime Minister Haider al-Abadi to send the army to Kirkuk and retake its oil fields. This is no small matter, as the fields hold some 4% of the world’s oil and produce hundreds of thousands of barrels a day.In response, Kurdish Peshmerga have been deployed in large numbers to the province. The problem the Iraqi army has with contesting Kirkuk is that the Peshmerga, US-led coalition and Iraqi Army are coordinating the campaign to defeat ISIS in Hawija.It is unlikely that regular army troops, with their American advisers, would get mixed up in a battle with Kurdish troops who are also close to the US-led coalition. However, the Shi’a militias, backed by Iran and officially part of the Iraqi security forces since 2016, could be used to create “provocations,” say Kurdish leaders. The militias number almost 100,000 men and are called Hashd al-Shaabi or Popular Mobilization Forces. They have been instrumental in most of the battles against ISIS and run checkpoints throughout central and parts of northern Iraq. Fighting has flared in the past in Tuz Khurmatu and Khanaquin, which lie on the fault line between control of Baghdad and the Kurdish Regional Government.“There is no Iraq, it is a militia state,” says Hussein Yazdanpanah, a Peshmerga leader and member of the Kurdistan Freedom Party who has fought on the Kirkuk front for years. “We are ready [to face] the Hashd and Iran and Iraq.”In the coming days, populist pressure from the Iraqi Parliament will try to force Baghdad to move against Kirkuk. However, countervailing pressures by the US-led coalition, Russia, and others will encourage Baghdad to engage in dialogue rather than spark a conflict.The Peshmerga, Shi’a militias and Iraqi Army have all fought ISIS for three years, but each force wonders what will happen when they come to blows. Kurds say they are ready for the eventuality and that without air cover from the coalition, the Iraqi forces cannot advance. But the Iraqis have also forged a strong force in battle in Mosul and Tal Afar.For now each side is eyeing the other and they know that the area around Kirkuk will play a major role in any future conflict.