The United States is unexpectedly pulling its troops from the border between north-eastern Syria and Turkey, raising questions over the fate of the area.
It will allow the Turkish military to launch an operation there against a Kurdish-led militia alliance that Western powers relied on to defeat the Islamic State (IS) group.
We’ve boiled down why it matters.
Why is Turkey planning an assault?
One main reason: Turkey considers the biggest militia in the Kurdish-led alliance a terrorist group. It says it is an extension of a Kurdish rebel group fighting in Turkey.
Turkish leaders want a 32km (20-mile) deep “safe zone” along the Syrian side of the border clear of Kurdish fighters. They also hope to resettle up to 2 million Syrian refugees currently living in Turkey there.
The Kurdish-led alliance says it will defend its territory and that the US is “leaving the area to turn into a war zone” and risking the re-emergence of IS.