“I have my doubts that ISIS can take Baghdad...That city fighting takes a lot of lives.”
I agree that Baghdad should be a lot harder. It has been purged of a lot of Sunnis, and De-Ba’athification has left fewer potential turncoats there to turn things over to the attackers. The Iranians and the Maliki Government have had some time to muster for a defense or counter-attack. Whoever controls Baghdad has a claim on the whole country, so the stakes are higher.
If the rebels are going to take Baghdad, they better do it quick, because it will probably get harder with time. ISIS alone has no chance, only a large mobilization of Ba’athists and Sunni tribes could pull it off, but even that would be likely to degenerate into a Stalingrad-like bloodbath.
The Sunnis would probably be wiser to consolidate all the easy pickings and prepare to defend them.
If they are Bat-Shit crazy enough to go for it - stock up on popcorn, because we will probably be able to see the smoke from outer space.
The lesson in Iraq is, it’s a lot easier to conquer an area than it is to keep it.