(CNN) As the mire in northern Syria deepens daily, what is the likely endgame or goal for Turkey? It's a NATO ally, but has just launched a military operation against a group the United States has trained and armed to fight ISIS over the past three years. Where does this go?

It is hard to imagine -- given the scale of forces the Turks appear to have deployed at this stage -- that they have the numbers to force their way into a huge swath of northern Syria, like the part-mountainous, Kurdish-controlled Afrin region, and hold it indefinitely.

That would be messy, result in some Turkish losses eventually and take a while. This is more likely about harassing the Syrian Kurds there into some sort of political arrangement.

Afrin is geographically an anomaly from the rest of Syrian Kurdish-controlled territory: stuck out to the west of the country, a significant distance from Syrian Kurds' traditional area of power and -- even since they took the town of Manbij from ISIS with US help -- still with a chunk of Syrian Arab rebel territory cutting it off.

Looking at the future geography and breakup of northern Syria post-ISIS, Afrin was a complex question to answer. Now it appears that Turkey's leaders -- as they see the Syrian regime consolidate control on Aleppo and move in towards Idlib, and as the Syrian Kurds get comfortable east of the Euphrates river with American backing -- want to define their terms.

Read More