When Iraq's Popular Mobilization Units (PMU), which are supported by Iran, showed up at Sinjar five months ago and began taking over control of villages from Yazidi forces known as the Sinjar Resistance Units, it became clear that Iran was interested in the area.

The PKK's main headquarters is in the Qandil Mountains in northeast Iraq near the Iran border. Sinjar — known to the Kurds as Shengal — is home to the Yazidis, a Kurdish religious minority, and is in northwest Iraq near the Syria border. Erdogan is interested because when the PKK came to the region in 2014 to fight the Islamic State (IS) and defend the Yazidis , they then refused to leave despite strong reactions from Turkey and the Kurdistan Regional Government (KRG) in Erbil, Iraqi Kurdistan. This eventually made Sinjar a prime target for Turkey.

He has followed up the threats with a series of air raids. The pro-government Daily Sabah reported Turkish forces killed 96 PKK fighters in the mountains of Qandil and Zap and destroyed or seized caches of PKK explosives. Turkey, the United States and the European Union consider the group to be a terrorist organization.

Turkey is working to make good on its threat to demolish PKK strongholds in Iraq by continuing to bombard the group's positions. Though such operations have been ongoing for years, Turkish President Recep Tayyip Erdogan stepped up the rhetoric earlier this month, vowing, “If the authorities there don’t solve the problems of Qandil and Sinjar and if [Iraq] does not undertake what is to be done, then we will raze those places to the ground."

DIYARBAKIR, Turkey — Sinjar, Iraq, is shaping up to be the essential gem in someone's crown, but there are several contenders. Turkey, Iran and the Kurdistan Workers Party (PKK) are all vying for control of the strategic area — all for different reasons.

The PMU also became the driving force of the Iraqi army's operation last month to recover Kirkuk from the KRG. Kurds said there were Iranian soldiers in the predominately Shiite PMU who, after helping to take over Kirkuk, headed north to Sinjar.

Turkey’s interest in Sinjar because of the PKK presence was understandable, but why was Iran, which had no religious or ethnic ties to Sinjar, suddenly so interested?

In 1991 during the first Gulf War, Iraq under Saddam Hussein had fired Scud ballistic missiles into Israel from Mount Sinjar. Some people are wondering if that's what Iran has in mind now.

Others, such as Mehmet Alkis, a doctoral student at Marmara University who closely monitors the Middle East and Iraqi Kurdistan, said Iran is also seeking to realize its dream of a Shiite crescent.

“Strategically and politically, Iran wants access to the Mediterranean. That's the best way to export its oil and gas. It is also true that it wants to secure itself against Israel. Iran wants to control a line from Sulaimaniyah, Kirkuk, [Sinjar] [all in Iraq], Rojava [northern Syria], Deir ez-Zor [Syria], Damascus and Lebanon that will be both its strategic corridor and the base of the Shiite crescent. [Sinjar] is right between Iraq and Syria,” Alkis told Al-Monitor. “This is a vital connection for Iran that will also enable it to sever the links between the Kurds."

Iranian control of Sinjar could be considered a threat to some, but Tehran is building strength to act as a deterrent force and isn't likely to engage in a direct war easily, according to Alkis.

Alkis attributes Turkey’s keen interest in Sinjar to the roles of both the PKK and Iran. "Turkey doesn’t want Sinjar to become a new Qandil to be used by the PKK [as a stronghold]. Turkey will not allow a Kurdish corridor to emerge, even if it is controlled by Iran, which could also be a threat against Turkey. Turkey’s goal is to sever the Kurdish links or control the area itself."

Alkis said he doesn't know if Turkey could manage to control the area or whether it has developed such a plan. But he does know Turkey doesn’t want Iran in the area any more than Erdogan wants the PKK there.

Mohammad Keyani, who was a deputy of the Kurdish Gorran movement in the Iraqi parliament from 2010 to 2014, is among those who see a potential Iranian angle. “Turkey and Iran are [vying for] Sinjar. For Iran, [Sinjar] is the key to an Iran-Syria connection via Iraq. If Iran can control [Sinjar], it will have easy access to Iraq, Syria and Lebanon. Also, don’t forget there are Sunni areas in [Sinjar]. To keep Sunnis under observation is important for Iran.

He added, "Syria believes that if Sunnis become stronger and Turkey continues supporting them, it could create trouble for Iran. To sever the ties between Sunnis in Iraq and those in Syria, border control is essential for Iran. As for the KRG, to control the Kurdish movements, especially the Syrian Kurds, Iran has to control [Sinjar]. The United States is sending weapons to Kurds via the Semalke crossing of [Sinjar]."

Keyani believes Turkey has additional reasons to be concerned with Sinjar: “First, it is close to the Syrian border. Syrian Kurds are now controlling a large territory. Turkey wants to end this. It doesn't want a [situation] similar to Iraq to emerge. Second, [Sinjar] is close to Tal Afar, where Turkmens live. Turkey still has historical interest, even ambitions, in Ninevah province. If it can’t physically control it, it will want to have a proxy" to do it, such as the Barzani family or former Ninevah Gov. Atheel al-Nujaifi, who is now commander of the Turkish-backed Ninevah Guard Sunni militia. "If you ask me, Barzani will regain his status with Turkey by preventing the other Kurds from gaining prominence.”

Keyani said that in the short run it won’t be possible for Iran to threaten Israel with missiles from Mount Sinjar. “It will not be easy to deploy those missiles, to bring them over. [However], a threat that can materialize in Iraq is a total takeover by Iran. But the United States will not allow that. That's why the United States opposed the [Kurdish independence] referendum. Americans wanted a strong Kurdish region that will have a strong influence on the central government. The United States didn’t want Iraq to fall under [Iran's control], but sadly the Kurds didn’t understand it,” he added.

Iran and Turkey, which had differences over Syria's civil war, found themselves on the same front when the issue became a Kurdish one. Yet these two countries, which have been competing for hundreds of years, can't agree to stay on the same line of action forever, even when the issue is the Kurds. At the end of the day, they will confront each other at Sinjar, if not militarily, then politically. Turkey, Iran or the PKK — whoever controls Sinjar — will have an indisputable advantage in Iraq and Syria. The domination of Sinjar will be vitally important to the future of the region's Kurds.