An imminent Turkish incursion into northern Syria appears to be redrawing the map of the Syrian conflict once again, expanding the territory under Turkish control and striking Kurdish forces along the border.
It will be Turkey's third incursion since 2016, after troops have already been deployed on the ground across a sector in northern Syria, mainly to contain Kurdish influence.
What does Turkey want?
Turkey has two main objectives in northeastern Syria:
1. Removal of the YPG from its borders, considering it a security threat.
2. Establishing an area inside Syria where two million Syrian refugees can be resettled.
Ankara has been pushing the United States to take part in a 32-kilometer "safe zone" in Syrian territory, but has repeatedly warned it could take unilateral military action, accusing Washington of dragging its feet.
More recently, Turkish President Recep Tayyip Erdogan has spoken of a deeper incursion into Syria beyond the proposed “safe zone” to Raqqa and Deir Ezzor, in order to allow more refugees to return to Syria.
The impact of the operation on the Kurds
The Kurdish-led Syrian Democratic Forces (SDF) have spent years expanding their control across northern and eastern Syria, with the help of the US-led coalition against ISIS.
The Kurds are a striking example of the gains made in the Syrian war, with their allies establishing governing bodies, with the assertion that their goal is autonomy, not independence.
But these gains could collapse altogether in the event of a major Turkish offensive that could plunge the region into war. The so-called Syrian Democratic Council said the attack would trigger a new wave of mass displacement.
The YPG is the largest faction of the SDF coalition and will depend on whether the United States will keep troops in other areas of the east and northeast of Syria.
A full US withdrawal would prompt the Turks to make further incursions, perhaps preferring the return of the Islamic State, or the attempts of the Syrian government, backed by Iran and Russia, to reclaim territory.
Last year, when the Kurds faced the prospect of a US troop withdrawal, they knocked on the doors of Damascus to talk to allow the Syrian government and its Russian ally to deploy at the border.
The talks have made no progress, but such negotiations could become an option again in the event of a larger US withdrawal.
How far can Turkey go?
Kurdish forces control the border area in the northeast, stretching 480 kilometers from the Euphrates River in the west to Iraq's borders in the east.
Turkey's military plans now appear to be centered around a border strip between Ras al-Ain and Tal Abyad, about 100 kilometers apart.
A US official said his country's troops had withdrawn from observation posts there.
Although under the control of Kurdish-led forces, it has historically had a strong Arab presence.
"This is an area inhabited by Arabs and Turkey has good relations with its prominent groups," said Ozgur Unlu Hisargikli of the German Marshall Fund.
He said the YPG, if it tried to keep land there, "would lose a lot of blood."
Turkey did not specify the scope or initial focus of the forthcoming operation. "The place, timing and scope of implementing measures to address security risks will be decided by Turkey again," a Turkish official told Reuters.
Russia and Iran
It is known that Russia and Iran strongly support Syrian President Bashar al-Assad strongly in contrast to Turkey and the United States, which called on him to step down and supported opponents fighting to overthrow him.
Russia says Turkey has the right to defend itself, but Kremlin spokesman Dmitry Peskov said on Monday that Syrian territorial integrity should be preserved and that all foreign military forces with an "illegal presence" should leave Syria.
If the United States withdraws all its troops from northeastern Syria, the Russian-backed Damascus government could try to regain control of most of the area that Turkey did not control.
There is no overt support from Turkey's Western allies for its plan to return 2 million Syrian refugees, and the main concern of the West is that the influx of Sunni Arab Syrians into the Kurdish-dominated northeast of Syria will change the demographics of the region.
The UN regional coordinator for the Syrian crisis said all sides should avoid displacement of civilians if Turkey launched the attack.
Assad and his opponents?
Although the territory in question is already outside the control of the Syrian government, the Turkish incursion will mean that the dominant entity in the region will shift from an unfriendly force (the Kurds) to Turkey and opposition fighters who want to overthrow Assad.
Damascus has long regarded Ankara as an occupying force with plans in northern Syria, and has sometimes signaled its willingness to strike a deal with the Kurds, although their recent negotiations have reached a dead end.
Chaos and state organization
The SDF has been conducting operations against the Islamic State's sleeper cells since the group seized control of its last stronghold earlier this year.
Kurdish leaders have long warned that the SDF may not be able to continue holding ISIS prisoners if the situation deteriorates in the event of a Turkish invasion.
According to the Foreign Relations Department of the Kurdish-led administration in northern Syria, the SDF is holding 5,000 fighters from Iraq and Syria, as well as 1,000 foreigners from more than 55 countries.
If there is chaos in the region, IS could seize the opportunity and rise again.