A day after invading northern Syria, Turkish troops continued to launch more strikes against the US-backed Kurdish YPG forces in the area around Manbij. Though the invasion started with chasing ISIS out of the town of Jarabulus, Turkish officials have made clear the operation is mostly about the Kurds.

Turkey’s state media described the shelling of YPG targets as “warning shots.” Kurdish officials complained yesterday that the strikes were “blatant aggression.” Turkish officials don’t appear to be contesting that fact, and have reiterated they’re keeping the Kurds from expanding, deploying more tanks into the country.

Officials also issued an ultimatum against the Kurds, giving them one week to scale back their presence near the Turkish border or else. Turkey has maintained the troops will remain in Syria until the concern about the expansion of Kurdish territory has been resolved.

The YPG controls a substantial portion of northeast Syria, and over the past week also seized virtually the rest of the city of Hasakeh in fighting with the military. Turkey’s primary objection right now is Manbij, which the US helped the Kurds capture, and which is on the western side of the Euphrates River. Turkey has repeatedly insisted that the river is a “red line” for them.