The Turkish Army appears to be preparing to throw some additional complexity into the already-eleventh-dimension-chess-game that is post-IS Syria by threatening portions of northwest Syria currently controlled by the Kurdish PYD Party "People's Protection Units" (YPG) armed forces.
The Erdogan government, much like the governments preceding it, sees the YPG as functionally indistinguishable from the Kurdistan Worker's Party, or PKK, and clearly now that the Islamic State is off the table and the endgame for Syria appears to be closing has decided to take action against the perennial bogeymen of the states of the Anatolian and the Fertile Crescent, the Kurds. Or, at least, one faction of that beleaguered people.
The YPG was central to the US drive to reduce the physical "state" of the Islamic State, providing the only really effective infantry for that campaign. On Tuesday a spokesperson for the "US-led anti-ISIS coalition" tossed the YPG in the Afrin region under the Turkish bus, noting that the YPG in northwest Syria were not within the coalition AO.
I'm not sure how this will work, given that the same article linked above claims that the Trump Administration's cunning Syria plan includes supporting some 30,000 "Syrian Democratic Forces" along the Iraq-Syria border, ostensibly to continue to hunt IS fugitives but strategically to interdict Iraqi and Iranian support for proxies inside Syria such as Hizbullah.
The SDF, however, is pretty much the YPG with ash-and-trash. The YPG fielded something like 50,000 troops, while the Arab portions of the SDF consist of two main groups, the Jaysh al-Thuwar that includes some Turkmen and Kurds but seldom put together more than 2-3,000 fighters, and the Jaysh al-Sanadid militia of the Shammar tribe centered in northeastern Syria and Anbar province in western Iraq. The Shammar could assemble 8-10,000 troops. If the YPG decide to grab their A-bags and beat cheeks there won't be enough "SDF" to provide an interior guard on a porta-potty.
And this is beside the whole "The Kurds get screwed again" meme which seems to be a Middle Eastern thing and one in which the U.S. plays it's own shameful part.
Leaving the YPG units in the northwest to be smashed by Turkish tanks after coopting them to help fight for U.S. political objectives would be in the great tradition of American expeditionary war; maybe the Kurds can find some surviving Vietnamese mountain tribe Mike Force guys who can teach them the Nung term for "buddyfucker".
Once again we're reminded, not so much of Trump Administration incompetence (although that certainly plays a role here), but of the fact that describing the United States' Middle Eastern policy as an actual "policy" - that is, as something developed with a thoughtful consideration of regional realities and American national interests - remains somewhere between risible and tragic.