Better than anything else I have come across, the two quotes below sum up, in just a few words, the enormous clusterfuck into which the USA is entering in its mission to "degrade and destroy" the ISIS.
I wouldn't want my country to help the defendants of Kobani because Kobani is held by the PKK, and Turkey has been at war with the PKK for 30 years. Why should we stand in the way of Isis on this particular occasion? After all, Isis has already carried out untold massacres in just about every other Syrian and Iraqi town that it has invaded to date. Why extend a degree of mercy to Kurdish terrorists that has been denied to the Christians of Maloula or Shiite Turkomans of Iraq? Let Isis carry on with its grizzly work. Our soldiers cannot be placed in the line of fire to rescue the same Kurds who were exploding land mines under their feet. Ahmet T. (comment) - Financial Times
The Sunni states are unable to defend the region from the disciplined, aggressive, but relatively small, lightly equipped forces of IS. Despite lavish expenditures, extensive training programs, and impressive numbers of battalions and squadrons, Gulf armies are deeply flawed by corruption, tribal and sectarian fissures, and poor leadership. There is no reason to expect reform, especially when outside forces are available to provide security. Regional security is also limited by sectarian hostility, which has reached new highs with the demise of Sunni control in Iraq and the rise of Iran's nuclear program. Shia troops from Iran are unable to act decisively in Iraq without triggering fears and reactions from Sunni states. Sunni troops cannot intervene without triggering the same responses in Iran. Brian M Downing - Asia Times
If this war goes much further and it certainly looks like going much, much, further, it could turn out to be infinitely more dangerous and destructive, for all concerned: humanly, economically and politically, than the war in Vietnam ever was.
The ways that this could all spin out of control are too uncountable for any amateur Cassandra like me to number. Conventional wisdom is that after the demise of the USSR, World War Three is unthinkable, but I think that if anyone in Hollywood were trying to dream up a way of starting it, America's entering this whirlpool would make for quite a believable scenario. DS