I have no doubt they want to draw the US into a protracted ground war (and idiots like McCain and Graham want to help them) and Mosul would be a great spot, see earlier allusion to Stalingrad. But it did not work for them in Kobane because while air power alone can not win a war the lack of air power can cost you one. And I don't think Obama is stupid enough to play that game with them.
This is not a question of fanaticism or stupidity. Their greatest victory was capturing Mosul. Now that they have it they can either try to keep it or run away. Running away might be smarter but they would pay a heavy political price. But they will pay the same price if they fight and lose.
Were I commanding ISIS, I would order a phased withdrawal after filling the town with booby-traps and leave a small force of dedicated fanatics to die in defense of the town. What would you do?
This is not a question of fanaticism or stupidity. Their greatest victory was capturing Mosul. Now that they have it they can either try to keep it or run away. Running away might be smarter but they would pay a heavy political price. But they will pay the same price if they fight and lose.
Were I commanding ISIS, I would order a phased withdrawal after filling the town with booby-traps and leave a small force of dedicated fanatics to die in defense of the town. What would you do?