The Kurds are a stateless people who live primarily in Iran, Iraq, Syria, and Turkey, although some Kurds live in Europe and North America.
In Syria, the Kurdish YPG, meaning People's Protection Units, fought as a part of the SDF and alongside US forces to defeat ISIS in the territory the Kurds call Rojava.
The SDF, which included Arab fighters, took as many as 11,000 casualties but largely drove ISIS from Syria.
As retired US Army Gen. Joseph Votel, who led US Central Command during the campaign against ISIS, wrote in The Atlantic on Tuesday, "Eventually, the YPG became the backbone of the fighting force against ISIS in Syria. Without it, President Donald Trump could not have declared the complete defeat of ISIS."
Kurdish forces control the northeastern part of Syria, as well as a sliver of land north of Aleppo. However, after Trump decided to abandon Syrian Kurds, who are under imminent threat of attack by Turkey, that territory may change.