Turkish President Recep Tayyip Erdogan penned an op-ed in the Wall Street Journal on Monday calling on the international community to halt Syrian President Bashar Assad’s assault on Idlib province, the last major redoubt of insurgent forces in Syria. “The world must stop Assad,” Erdogan declared.

Erdogan made Turkey’s concerns clear up front, citing the 3.5 million refugees from Syria already living in Turkish camps and warning the Idlib operation will unleash a new flood of refugees, straining Turkey’s resources and jeopardizing its security. The United Nations on Monday reported 30,000 people have already been displaced by Russian and Syrian bombing on the outskirts of Idlib and another 800,000 could be driven from their homes by a sustained military campaign.

Erdogan also made a point of repeating his concerns about the threat posed to Turkey by terrorist organizations such as “the so-called Islamic State and the PKK.”

The latter organization is the Kurdish separatist movement that Erdogan invaded Syria to suppress. Turkey considers all armed Kurdish groups in northern Syria to be allied with the PKK, including the Kurdish militia supported by the United States as battlefield proxies against the Islamic State. Turkey’s war against the Kurds became a major diplomatic conflict with the U.S. that threatened to become a military confrontation, a situation the U.S. has been attempting to quietly defuse by convincing Kurdish militia to fall back from the Turkish border.

Having aired his own security grievances, Erdogan proceeded to blast Russia and Syria for claiming the invasion of Idlib is necessary to defeat terrorist forces such as al-Qaeda and ISIS:

The Assad regime seeks to legitimize its imminent attack on counterterrorism grounds. Make no mistake: No country appreciates the need to combat terrorism better than Turkey, which has suffered severely from terrorist attacks since the Syrian conflict began exporting insecurity throughout the region. But Bashar Assad’s solution is a false one. Innocent people must not be sacrificed in the name of fighting terrorism. This will only create new hotbeds of terrorism and extremism. The rise of ISIS was an outcome—not the cause—of what was happening in Syria. The international community must contain such violence to stop terrorism from taking root.

In Idlib, we face similar challenges. Certain designated terrorist organizations, including Hayat Tahrir al-Sham, remain active in this area. Yet those fighters account for a fraction of Idlib’s population. In order to eliminate terrorist and extremist elements in Idlib and to bring to justice foreign fighters, a more comprehensive international counterterrorism operation is necessary. Moderate rebels played a key role in Turkey’s fight against terrorists in Northern Syria; their assistance and guidance will be crucial in Idlib as well.

Preventing the assault on Idlib need not set back counterterrorism efforts. Turkey has succeeded in fighting terrorist groups, including ISIS and the PKK, without harming or displacing civilians. In order to restore some level of stability to affected areas, dozens of Turkish servicemen and servicewomen have lost their lives. Turkey’s ability to maintain order in Northern Syria is proof that a responsible approach to counterterrorism can win hearts and minds.

The Turkish president put his finger on the dispute that will shape the final stages of the Syrian civil war: Assad and his Russian patrons consider all rebel forces to be “terrorists” in need of crushing, including those who worked with Turkey, Europe, and the United States against ISIS. Turkey, in turn, disagrees with Europe and the United States about the Kurds.

Russia and Syria want to press ahead with the Idlib offensive because they want to hammer the final nails into the coffin of the “political solution” in Syria demanded for years by the Western world. The United Nations envisions a “peace process” in which the grievances of moderate rebels are addressed and the Syrian government is reconstructed without Bashar Assad in control.

Russia and Syria responded by sabotaging the U.N. peace initiative at every turn, running their own parallel “Astana process” out of Kazakhstan – a process that deliberately excluded enough major Syrian rebel groups to ensure it would never produce a comprehensive political solution – and industriously killing enough rebels to sweep unseating Assad off the table. Years ago, Moscow occasionally grumbled that perhaps Assad should think about retiring, but now there is no talk whatsoever of a post-Assad Syria.

Smashing the rebels in Idlib will turn the “political process” into surrender negotiations for the remaining insurgents, and the terms will not be generous. Killing civilians in Idlib who rejected Assad’s rule will be an objective for Russia and the Syrian military, not an unfortunate side effect.

Neither Moscow nor Damascus could possibly care less about triggering another refugee tidal wave that further weakens Turkey and Europe. Pro-Erdogan media in Turkey has been churning out ominous maps showing prospective Idlib refugees how they can march right through Turkey without stopping and settle in Europe.

Erdogan understands this – he is certainly no stranger to brutal authoritarian thinking – and said as much in his op-ed:

All members of the international community must understand their responsibilities as the assault on Idlib looms. The consequences of inaction are immense. We cannot leave the Syrian people to the mercy of Bashar Assad. The purpose of a regime offensive against Idlib would be indiscriminate attacks to wipe out its opposition—not a genuine or effective campaign against terrorism. A regime assault would also create serious humanitarian and security risks for Turkey, the rest of Europe and beyond.

It is crucial for the U.S., which has concentrated on chemical attacks, to reject its arbitrary hierarchy of death. Conventional weapons are responsible for far more deaths. But the obligation to stop the next bloodshed is not the West’s alone. Our partners in the Astana process, Russia and Iran, are likewise responsible for stopping this humanitarian disaster.

Idlib is the last exit before the toll. If the international community, including Europe and the U.S., fail to take action now, not only innocent Syrians but the entire world stands to pay the price. Turkey has done everything in its power to stop the bloodshed next door. To ensure that we succeed, the rest of the world must set aside narrow self-interest and throw its weight behind a political solution.

The hard truth about Syria is that all parties have made terrible miscalculations based on single-minded objectives and domestic political concerns, with one exception: President Bashar Assad. His goal was always to murder and purge rebel elements and resume unchallenged control over a smaller, more tractable population. Only one great massacre remains to achieve that goal. No one is going to talk Assad, Putin, or the tyrants of Tehran out of perpetrating it.