The headline is right, not you. They are "Syrian forces" - specifically, Kurds who make up the YPG, and they are doing the fighting along with U.S. bombing Still, it's a sort sighted move by the Trump administration - the YPG has been accused of ethnic cleansing among other atrocities and is not a Western ally. 
"The YPG is the Syrian arm of the Kurdistan Workers Party (PKK), which is designated by the United States as a terrorist organization for the acts of political violence it has been responsible for against NATO ally Turkey for decades."
 - https://www.lawfareblog.com/we-are-rushing-raqqa
 Trump's ill advised policies (like cozying up to this group) are alienating and angering their  (and our) allies.