Turkish tank in Afrin
© UnknownTurkish hardware arrayed against the Kurds in Afrin
As Turkish military and Syrian Islamist rebels in their employ try to overrun the Kurdish-held Afrin enclave in northwestern Syria where there is no US presence, they have has also stepped up the pace of airstrikes, artillery barrages and ground skirmishes against the Kurdish YPG militia near the the northern Syrian city of Manbij where the Kurdish forces are closely intertwined with US troops.

It is almost certain that US troops are in some way involved in these clashes and occasionally imperiled by the rebels and the Turks, seeing how not only do we know that they are there, but that the Pentagon has confirmed earlier this month that US troops in that area are "regularly" fired upon and "occasionally" fire back.

So in fact, taking place in Manbij are acts of war of one NATO member against another. There is non-trivial chance this will degrade into a full-blown Turkish-American clash.

The Turkish leader, Erdogan has now promised that when the Turkish-rebel coalition is successful in Afrin he will launch another offensive to dislodge the US-backed Kurdish militias from Manbij as well:
"'Operation Olive Branch' will continue until it reaches its goals. We will rid Manbij of terrorists, as was promised to us before. Our battles will continue until no terrorist is left right up to our border with Iraq," Erdoğan said in an address to ruling Justice and Development Party (AKP) colleagues in Ankara on Jan. 26.
Meanwhile Erdogan's foreign minister has said Ankara wants to see US withdraw from Manbij immediately.

liveumap of turkish attacks near Manbij
© UnknownTurkish strikes on Kurdish-US held Manbij territory on January 26th
The Turkish leader being a notorious blowhard it would be easy to dismiss all of this as more of Erdogan's bluster. After all the promise to march onto Manbij was made in a speech to his party faithful. His minister likewise was speaking to a smattering of Turkish journalists.

Trouble is most people, including me, likewise dismissed his threats that he would invade Afrin, but finally he did. He is a blowhard who occasionally carries out his threats and isn't afraid to roll the dice as the Russian air force, Assad, ISIS, Gulenists, Turkish Kurds and others Erdogan has struck unexpectedly, often in the back, can attest to.

A NATO-on-NATO clash in Syria is perhaps not likely, but it would take a braver man than I to rule out completely.

The Kurdish YPG took Manbij from ISIS with extensive US help in the spring of 2016. At the time Erdogan threatened the YPG crossing over from Kobane to Euphrates' right bank was a red line for Ankara that would prompt a Turkish military intervention.

US backed the Kurdish offensive anyway, but assured Turkey that once the military part of the offensive was over YPG fighters would retreat back east across the river.

This never happened and the area, mainly populated by Arabs, continues to be heavily garrisoned by Kurdish fighters to this day.

The Kurdish offensive against Manbij then directly led to the Turkish Euphrates Shield offensive to take ISIS-held al-Bab in northern Syria and therefore eliminate the possibility the Kurd could link up Kobane and Afrin as was their strategic goal.