Turkey followed on its words and invaded Syria, Afrin to create a buffer zone.
Apart the possibility of errors this situation begs some dig in.
It all started with the US idea of forming a 30,000 Kurdish force as a buffer to prevent Islamic State return (in reality it was done to carve a US – allied part of Syria).
Now we find a NATO-US ally attacking the YPG Kurds – US ally. This could have never have happened (a NATO ally member attacking a US ally) if President Obama did not respect the famous red line on Syrian gas attack.
It has forever weakened the US standing (well unless the US changes idea).
Afrin will fall (Turkey has the second largest NATO army), but things get complicated if then the Turks will try and seize Manbij. All the American strategy kind of pivot on Manjib and practically a fall of Manjib will be a fall of the US influence in Syria.
The US probably will not intervene unless shot upon and Syria will be lost.
Definitely the Turks made an agreement with the Russians (Russians owns the sky with missile defenses and it would be impossible for Turkey to attack without their consensus).
The Russians will not be super -happy, but it is better Turkey than the US and they had to pay back the US as President Trump authorized the sale of lethal weapons to Ukraine. They probably also helped carve some deal with Assad (Turkey is not really interested in invading Syria – they just do not want a US armed Kurdish force at their doorstep).