On Sunday, clashes broke out in northern Iraq between a group of Yazidi paramilitaries and members of the Iraqi army. The Iraqi army claims that a force of the Kurdistan Workers Party (PKK) attacked a checkpoint, resulting in deaths on both sides. The serious incident – in the Sinjar area where ISIS attempted genocide against members of the Yazidi minority – will raise concerns about instability but it is also part of a larger regional attempt to crackdown on groups connected to the PKK.On March 6, Turkey and Iran said they were planning to work more closely to confront the PKK. “God willing, we will carry out a joint operation against the PKK, together with Iran,” Turkish interior minister Suleyman Soylu said, according to the Kurdish media outlet Rudaw. At the same time, Iraq and Iran are talking about implementing a 1975 agreement that aims to cut down on each country’s supporting Kurdish groups in the other country. Turkey is also pushing for Syria to adhere to the 1998 Adana agreement that would require Syria to work to expel the PKK.To understand why these historic agreements are suddenly in the news, it is important to look back over the last several years in the region. The PKK is one of several important groups that operate among Kurds in the Middle East. Although it has historically been active primarily in Turkey, it has branches in Iraq, Syria and Iran. Founded in the 1970s the far-Left group fought a long war against Turkey in which thousands were killed. Turkey confronted what it saw as an existential terrorist threat with heavy-handed military operations. Eventually, in the 1990s, Turkey also sent troops into northern Iraq to seek and destroyed PKK bases. The PKK has had bases in the Qandil Mountains in northern Iraq, and Turkey has frequently launched raids against them. Turkey also sought to stop Syria from hosting the PKK in 1998 with an agreement that led to the expulsion of PKK leader Abdullah Ocalan. He was captured in Kenya in 1999.Turkey and the PKK attempted a ceasefire in 2013. This came amid rising instability in Iraq and Syria. In Syria, the People’s Protection Units (YPG) – which is linked to the PKK – became a key player in eastern Syria and was a major driving force behind the Syrian Democratic Forces which helped defeat ISIS. The YPG also ran Afrin in northwest Syria, a Kurdish mountains area on the border with Turkey. For a variety of reasons, the ceasefire broke down in 2015 and Turkey decided that it would seek to destroy the PKK in Turkey and in neighboring countries. The aftermath of the ceasefire breakdown was a brutal and difficult conflict in Kurdish cities in eastern Turkey in 2015 and 2016. The PKK was defeated in Turkey and Ankara began jailing members of the People’s Democratic Party (HDP), the left-wing Turkish party which Ankara now accuses of being linked to the PKK. It arrested Selahattin Demirtas – the HDP leader – and numerous other HDP lawmakers. Growing centralization of power in Ankara after the 2016 attempted coup has meant more flexibility in how Ankara uses the armed forces against the PKK.Since then, Ankara has launched two major military operations in northern Syria, both designed to reduce the YPG’s power. Its operation in Jarabulus was ostensibly against ISIS, but it was also to prevent the YPG from moving beyond the town of Manbij and linking up with Afrin. Turkey has said it will not allow a “terrorist corridor” along its border. Turkey also launched the 2018 Afrin operation for the same reason. Ankara has warned the US that eventually, Turkey will also seek to push the SDF and YPG out of Manbij and other border areas, where it has demanded control over a “safe zone.”This Turkish policy is linked to US President Donald Trump’s decision to withdraw from Syria. The US has sought to balance its close work with the SDF against ISIS with telling Ankara it is concerned about its security also. Towards that end, the US announced $12 million bounties on three PKK leaders in the fall of 2018. But Turkish pressure has not prevented the US from continuing its work with the SDF.Meanwhile, Turkey has been launching more raids into northern Iraq in April 2017 and August and December 2018. Turkey has struck areas in northern Iraq, where Yazidis who joined PKK-linked units are present. For instance, Zeki Shingali – a Yazidi leader returning from an event memorializing the ISIS genocide – was struck by Turkey in August 2018. He was accused of being a senior PKK leader.Turkey has demanded that the Iraqi government remove the PKK from Sinjar. This is a complex issue because it was the YPG in 2014 and PKK fighters who helped stop the ISIS genocide against Yazidis. But from Turkey’s point of view, Sinjar is “another Qandil” and it wants Iraq’s cooperation to remove the PKK. In April 2018, the PKK claimed to have left Sinjar.From Ankara’s perspective, the PKK was able to flourish in the years 2015-2018 because of the instability in the region. This is why Turkey routinely says it is fighting ISIS and the PKK, trying to link both groups as those who flourished under instability.With the conflict against ISIS winding down, Turkey has decided it will work closely with all its neighbors to destroy the PKK. This has meant that Turkey is willing to compromise with the Syrian regime – which it had previously opposed. Turkey had backed the Syrian rebels, now it has curtailed them and sought to redirect the Turkish-backed Free Syrian Army to fight against the YPG in Afrin and Manbij. It wants to co-opt the Syrian rebellion for its own anti-PKK policy, and it has been successful.Turkey also harshly condemned the Kurdistan independence referendum in northern Iraq in September 2017, even though the referendum was pushed by the Kurdistan Democratic Party (KDP) which is historically opposed to the PKK and closer to Ankara. Turkey didn’t want the Kurdistan Regional Government in northern Iraq to become more autonomous, at least in part because it doesn’t want the PKK to continue having bases there.Turkey has expanded its military operations in northern Iraq in the last two years. It has encouraged Iraq to control Sinjar and prevent any PKK members in Sinjar from transiting to Syria.Now, Turkey also wants to work more closely with Iran, prodding Tehran to conduct a joint operation. Iran has faced off against its own PKK-linked group called PJAK. PJAK has been cautious about launching any kind of an insurgency in Iran because it understands how precarious its situation is. But Turkey seems to think that it can get Iran to dismantle PJAK at the same time it gets Iraq to use a heavier hand in Sinjar. The clashes in Sinjar this week may have been related to this new policy.The last piece of the puzzle for Ankara will be to try to find a way to reduce US support for the SDF and to defeat the SDF in eastern Syria. This could also mean working more closely with Russia, the Syrian regime and Iran. It wants Iran and Russia to prod the Syrian regime to oppose the PKK. It successfully got Russia to not include any PKK-affiliated groups in meetings regarding Syria, even though other Syrian opposition groups are invited. It also hopes that if the US withdraws forces that it can agree with the Syrian regime to allow an operation along the border, similar to Afrin, removing the YPG from the border area.This is a driver of Turkish policy in the region and it is one reason Turkey is working so closely with Russia and Iran. Although the US is careful to continue to tell Turkey that the US relationship with the SDF is temporary and transactional, Turkey knows the US wants to stay in eastern Syria. For instance, when news broke on Sunday that the US might keep 1,000 troops in eastern Syria, the US Chairman of the Joint Chiefs Joseph Dunford tweeted that the US would continue to “conduct military planning with the Turkish General Staff to address Turkish security concerns along the Turkey-Syria border.”The last four years of Turkey’s policy in the region should be seen in the context of the decision by Ankara to destroy the PKK once and for all. It began with the 2015 crackdown after the HDP did well in parliamentary elections and after the ceasefire broke down. This continued into the Turkish offensives into Syria, largely designed to reduce the power of the YPG. Then Turkey began to reach out to Iraq regarding Sinjar and Iran regarding PJAK. At each step, the concept is to surround eastern Syria with close Turkish allies in Iraq’s Sinjar, in the Kurdistan Regional Government and Iran. Then, stifled, Turkey reasons that the SDF will be forced into a deal with the Syrian regime and the US will accept a Turkish offensive. With that, the last four years of PKK investment in eastern Syria – through its allies and linked-groups – will be ended, and the PKK will find itself under siege in what remains of its networks in Turkey, Iran and Iraq. This is what guides Ankara’s policy.