The_Doctor The_Doctor:
If we leave from the middle east and central Asia. Things will be much calmer.
If we leave from the Middle East then the following will happen in short order:
Iran goes to war with *everyone*.
Israel will use one or more nuclear weapons in response to a similar attack likely on Haifa or Tel Aviv. Maybe even 200 of them as this is one of their not-so-secret policies about such attacks.
Turkey will invade northern Iraq and conduct a genocide against the Kurds.
Pakistan and India will go to war again and maybe even draw China into it.
If we fold in Central Asia then both China and Russia will need to go back in - as both of them want to do in order to control Muslim violence that's spilling across their borders. Maybe they'll do it peacefully, maybe it will be a bloodbath, in any case all either country will care about is the mission at hand and Western sensibilities will be meaningless to them.
In the long term our absence from the region will allow local nuclear programs to progress unimpeded. That an Iranian or Arab produced nuke could be used against the West is a near certainty. I keep a huge amount of iodine tablets at home against this probability.
That the West will settle for nothing less than retaliatory annihilation is an absolute fact of policy. No Western government could long endure that allows a city or cities to be immolated while sitting on its hands.