“I am overwhelmed,” writes Don Lemon, leaving the American cable news network after 17 years on the job.

JUDY WOODRUFF: A long-standing rivalry between vital American allies has flared up in Iraq today.

Iraqi forces and militias have moved in to push Kurdish forces out of the disputed northern city of Kirkuk.

Lisa Desjardins starts our report.

MAN (via interpreter): Commander-in-Chief of the Armed Forces Dr. Haider al-Abadi ordered the people of Kirkuk to be protected and the city to be kept safe.

LISA DESJARDIN: After months of mounting tensions, Iraqi federal troops moved to retake the disputed city of Kirkuk from Kurdish forces.

The effort began before dawn. By noon, Iraqi soldiers, along with state-backed militias, quickly took control of several large oil fields north of the city. The Iraqis also took over Kirkuk’s military airport and various government buildings. They flew at half mast what was a symbolic Kurdish flag on the governor’s territory.

Journalist Rebecca Collard from Erbil was in Kirkuk this morning.

rebecca COLLARD, Journalist: There were some clashes, shooting in the distance, but for the most part the city seemed more or less abandoned. So, by the end of today, the Iraqi army actually controlled the entire city and many suburbs of Kirkuk.

LISA DESJARDIN: A spokesman for the Iraqi Shiite militia said they achieved all their goals without much resistance.

AHMED AL-ASSADI, Al-Hashed al-Shaabi spokesman (via interpreter): As the troops approached the area, they encountered several insurgents who were trying to block the advance of the advancing units. Our troops returned fire and drowned out its source.

LISA DESJARDIN: It comes three weeks after the Kurds held a non-binding independence referendum involving the disputed province of Kirkuk.

More than 90 percent of the inhabitants of the Kurdish region voted for secession from Iraq. The Iraqi federal government, Turkey, Iran and the United States have rejected the desire for independence.

The multi-ethnic region of Kirkuk is located near the autonomous Kurdish region in northern Iraq. Kirkuk, which is called the oil capital of the country, produces about 500,000 barrels per day.

In 2014, during an ISIS offensive into Northern Iraq, the Kurds took control of Kirkuk and the Iraqi military fled the city. Three years later, the Kurds, led by their president Massoud Barzani, sought to consolidate their power despite tensions with the central government.

Kurdish officials today accused Iraq of carrying out a major complex attack.

MAY. GENE. AYUB YUSUF SAID, Peshmerga Commander (via interpreter): I don’t know exactly what’s going on because we’ve been in this fight since 4:00 am. We have suffered losses, including martyrs, and have now withdrawn to this position. Some of the other Kurdish forces left. They didn’t fire a single shot.

LISA DESJARDIN: While the Kurdish forces withdrew from their posts south of the city, some residents vowed to die in battle. Thousands of others fled north.

REBECCA COLLARD: In the past few years, Iraqi forces, primarily the Shiite militias, Hashed Shaabi and Kurdish forces have been focused on fighting ISIS. Now this fight is coming to an end, and there are fears that now these internal divisions in Iraq will become more obvious and perhaps more violent.

LISA DESJARDIN: In these clashes, one armed force, mostly armed by the Americans, is opposed to another. Both Kurdish forces and Iraqi government forces are part of the coalition fighting ISIS. The US sought to downplay the fighting, calling the shootout a misunderstanding.

And in the Rose Garden, President Trump tried to remain neutral.

PRESIDENT DONALD TRUMP: We don’t like the fact that they clash. We don’t take sides. But we don’t like the fact that they clash.

LISA DESJARDIN: For the PBS NewsHour, I’m Lisa Desjardins.

JUDY WOODRUFF: Emma Sky joined me to learn more. She served as an adviser to General David Petraeus when he was commander of US forces in Iraq from 2007 to 2010 and to Faisal Istrabadi. He is a former Iraqi ambassador to the UN and was involved in the drafting of Iraq’s interim constitution.

Welcome to both of you.

Let me start with you, Emma Skye.

It happened so fast. What exactly did the Iraqi government do?

EMMA SKY, Yale University: The Iraqi government moved its forces north to Kirkuk.

And since 2003, the Kurds have made it clear that they want to include Kirkuk in their territory in order to continue gaining independence, which has always been their goal. But Kirkuk is important to Iraq itself, and no Iraqi prime minister can afford to lose Kirkuk.

So you can see this reaction after the September 25th independence referendum, which also covered the disputed territories and the city of Kirkuk.

JUDY WOODRUFF: Faisal Israbadi, what can you add to why the Iraqi government is so determined to take over the city?

FAISAL ISTRABADI, Former Deputy UN Ambassador to Iraq: Well, several reasons.

First, as Emma just said, this is part of the disputed territories that are legally and constitutionally under the jurisdiction of the federal government in Baghdad. The PKK expanded into these disputed areas at a time when ISIS was expanding its territory and then began taking steps to unilaterally announce that these areas are now included in Kurdistan, including during the referendum Emma referred to.

It provided for a referendum to be held in these disputed territories. Now, as long as Iraq — as long as we’re talking about one country, it doesn’t really matter who controls Kirkuk, but after the referendum, that gave rise to the second reason why Baghdad decided to act now.

As Emma said, Kirkuk is an important oil producing area in Iraq. And this is vital to the economic viability of an independent Kurdish state and an important part of the economic viability of the Iraqi state. Thus, I think there will never be a scenario in which Baghdad allows the Kurds to unilaterally exercise control over Kirkuk while independence is on the negotiating table.

JUDY WOODRUFF: Emma Sky, we heard President Trump say today that the US is taking no sides in this.

Is it true that the US does not take sides? What is the US role here?

EMMA SKY: Well, the US has said over and over again that its policy is to support a unified Iraq.

So you see the US has supported the Iraqi security forces as well as the Kurdish Peshmerga in the fight against ISIS. US policy in the past few years has indeed been focused on ISIS, not the day after ISIS.

But what we are seeing at the moment is that various groups are already moving over the next day, which is a power struggle for control of various territories in Iraq.

And Barzani believed that during the fight against ISIS, he became stronger because he received weapons directly from the international community. And, as Faisal said, he was able to extend his control over the disputed territories.

He also faces internal problems in Kurdistan. Tensions exist between various Kurdish groups, and some believe that Barzani has outlived his presidential term.

JUDY WOODRUFF: Which reminds us how difficult it is, Faisal Istrabadi.

What does the Iraqi central government want here? They are not going to get rid of the Kurds. What do they want?

FAISAL ISTRABADI: Oh, well, I mean the Kurds are, of course, a vital part of Iraq. They are a vital part of the political process and they were introduced in Baghdad. The President of Iraq has been a Kurd since 2005.

I think that should happen, and I hope that the government of Iraq wants a negotiated settlement in which neither side dictates terms to the other, but a negotiated settlement.

Look, Erbil has legal agreements regarding Baghdad. Baghdad has legitimate arrangements for Erbil. I think we may need a mediator or someone to call a roundtable – I mean the United States of course – to address some of these issues.

Most of the problems on Erbil’s side are related to the economic issues of payments, and on Baghdad’s side, the transparency of how much oil Erbil produces and exports, which Erbil has never reported to Baghdad.

I think that if these issues are resolved, perhaps some of these other issues can be put off until at least another day. But in the end, neither the government – nor the regional government, nor the federal government in Baghdad – can truly tolerate the dictation of terms by the other side. I hope that a settlement agreement will be reached through negotiations.

JUDY WOODRUFF: Emma Sky, where do you think it’s going to go next? Do you see the peace that various parties in Iraq have worked hard to create is crumbling as a result?

EMMA SKY: I think there is room for a deal, and I think that such a deal that could be negotiated is about the special status of the city of Kirkuk and the agreed terms for secession of Kurdistan, be it confederation or independence.

But there must be negotiations. Consideration needs to be given to where the border between Iraqi Kurdistan and the rest of Iraq should actually be, and this requires mediation between areas in these territories.

JUDY WOODRUFF: Well, we know that there are other players that are playing an important role here in Iran and Turkey, and it all plays out very strongly as we watch, watch it happen in Iraq.

Emma Sky, Faisal Istrabadi, thank you very much.

FAISAL ISTRABADI: Thank you.

EMMA SKY: Thank you.

The post “Why Kirkuk is in the middle of a power struggle” first appeared on the PBS NewsHour.