Turkey has been complaining about US support for the Kurdish YPG for years, and this weekend, that has boiled down to an overt ultimatum, with Turkey’s Foreign Ministry demanding the US immediately withdraw from the Syrian city of Manbij.
The US helped the YPG capture Manbij early last year, and Turkey has been mad because their position is the Kurds can have no territory west of the Euphrates River. Though Manbij is on the river, it is primarily on the western bank.
With Turkey’s recent invasion of the Afrin District, they’ve made it clear that Manbij will be their second target in the invasion. This could be a potential problem, since the US has troops in the city, which were put there in the first place to preclude a Turkish invasion.
In recent days, Turkish officials have suggested they are willing to not only invade whether the US leaves or not, but suggested that US troops would be targeted if they continue to help the Kurds in the city.
This risks being a long-term issue for the US beyond Manbij, however, as Turkey has said all of Syrian Kurdistan is a target, and all US troops in Syria are deployed into Kurdish territory, meaning this could boil down to Turkey forcing a US pullout.
Turkey is claiming a US concession already made, in that the US supposedly has pledged a halt to all arms for the Kurds. This is a long-standing Turkish demand, but the US has yet to confirm that this indeed will be the case.