Things are about to get very interesting and very uncomfortable for NATO.  President Trump has announced that Turkey is about to launch a unilateral invasion into Northern Syria… There is going to be a scramble amid many geopolitical interests.

First, the announcement:

[White House]  –  Today, President Donald J. Trump spoke with President Recep Tayyip Erdogan of Turkey by telephone. Turkey will soon be moving forward with its long-planned operation into Northern Syria.
The United States Armed Forces will not support or be involved in the operation, and United States forces, having defeated the ISIS territorial “Caliphate,” will no longer be in the immediate area.

The United States Government has pressed France, Germany, and other European nations, from which many captured ISIS fighters came, to take them back, but they did not want them and refused.
The United States will not hold them for what could be many years and great cost to the United States taxpayer. Turkey will now be responsible for all ISIS fighters in the area captured over the past two years in the wake of the defeat of the territorial “Caliphate” by the United States.  (more)

Next let’s establish the foundation for the scramble:
♦There was a 2014 Authorization for Use of Military Force (AUMF) voted and approved by Senate committee permitting military action in Syria against the backdrop of chemical weapon use and terrorism – it never went anywhere.  The Obama administration used the Bush-era AUMF directed at combating terrorism. With ISIS defeated by President Trump that sketchy 2002 interventionist authorization ends.
♦Also remember in October 2014 then Vice-President Biden accidentally told the truth when he told an audience that Recep Erdogan was specifically responsible for the rise of ISIS in Syria; and that Turkey had actually armed al-Qaeda, al-Nusra, ISIS, and provided assistance.

• Turkey is a member of NATO.
• Turkey has previously used its NATO membership as a shield to stop threats from Russia.  Remember Turkey shooting down a Russian fighter jet?
• Turkish President Recep Erdogan is a manipulative bad actor; a hostile dictator; and sympathetic to extremes within political Islam.  Erdogan has openly showcased his friendship with the Muslim Brotherhood.
• Europe draws exclusive benefits from NATO defenses.  Europe would not take back the ISIS fighters captured in Syria that were EU nationals.
• The ISIS prisoners we turn over to Turkey will be regarded less as prisoners, and more likely considered heroes by Erdogan’s govt. Remember, Erdogan gave the Muslim Brotherhood’s leadership safe harbor in Turkey after they were kicked out of Qatar.
• Unfortunately, it is likely Erdogan will attack the Kurdish forces in Northern Syria.
• The Kurds are U.S. allies; and this will be the point of contention for the neocons.
• Turkey will invade NE Syria, but -depending on current strength- Turkey runs the risk of a counter-attack by the Syrian Army, and potentially Russia.

With the European nations, NATO allies, refusing to take their ISIS fighters back as prisoners, President Trump has made a deal with Erdogan to take them.
In the announcement President Trump has made it clear that any action by Turkey into Syria is unilateral; there will be no assistance by the U.S. on any aspect; including if Turkey is counter-attacked by Russia/Syria or organized Kurdish forces.
Essentially, Trump is leaving Erdogan naked to a myriad of his enemies if Erdogan does cross the border.  The U.S. part of the NATO shield is removed.  The Europeans will likely not evoke the NATO defense treaty without the U.S.  Heck, the EU is essentially spineless without the power of the U.S. military.
President Trump is calling out the duplicity of the entire situation by calling all of their bluffs.  President Trump is calling-out: NATO, weak EU ‘allies’ and Turkey.
In essence, this White House announcement is a major Gordian knot being cut.
It is unlikely President Erdogan expected to have this framework made so public.  This rather loud declaration by President Trump seems strategic in that it could make duplicitous Erdogan think twice about the actual military invasion itself.
However, Erdogan is also a rabid ideologue and he wants to recreate the Ottoman empire… so he’ll likely go ahead regardless of cost.
Down the road…. instead of those ISIS prisoners being held in European jails; and considering the sympathetic Turkish handlers; those ISIS fighters will eventually make their way home without anyone knowing.   However, the EU has created that issue by refusing to step-up and take ownership.
That same weak European mindset could likely be facing another challenge surrounding what to do about NATO if Turkey loses this gamble.   However, again, another issue created by Europe.
FUBAR.
…But we’re out!