They've done it twice before. Fallujah and Ramadi were declared hot zones. When Marines pushed Falljuah in 2004, we basically said "If you want to play, stay, everyone else get out." They stayed, and everyone in that city was hot. We did the same thing in Ramadi in 2006. They stayed. They'll meet us in open combat, if we allow it to happen. We actually avoid the fight, by allowing civilians to remain in the city, and then use US military to "police."
To put it into more pointed terms... the only solution I can agree with: Call for a UN Resolution. Send in a reinforced MEU along with other members of the UNSC (a la ISAF). This is the same path we took for Afghanistan and is the only path I would agree with. No more "lone wolf F(*& the world" wars. Send in a reinforced MEU along with whatever folks the remaining UNSC send in. Let the UN take the reigns to stabilize the region. Perhaps a more moderate Iran (we can hope) will be the lynchpin that exists now that didn't exist in 2008. I can only see Iraq fracturing to a Sunni Iraq, Shia Iraq and Kurd Iraq.
When dealing with an enemy that only comprehends the language of violence, speak to them loudly in their chosen tongue.
You know, it sucks that they mostly kill our civilians and we can't even touch them unless they are actively sending projectiles in our direction.
Or, conversely, a bunch of randos in Iraq see Jihadist Jim plant the bomb and are terrified of him so they don't say anything to the US who killed a bunch of their relatives in a ")(@*& EM ALL" attack? Afghanistan resulted in a case study of relations between ISAF and the tribal leaders and we stopped indiscriminately shooting at them and killing them. We paid for damages we inflicted on their towns and, lo and behold, we started getting actionable intelligence and cooperation from them.
Which puts US back into a police role, because who is going to enforce UN resolutions in country? We are not good at policing. And we're terrible at politics.
I've been saying it since we began this entanglement in the sand and mountains of the Middle East. We have the tool to open the gates of Hell for those idiots. An army that can match any terrorist organization bloodlust for bloodlust is at our disposal. Barack Obama's next words should be "Turkey, it's time to justify your spot in NATO."
Which is exactly why we should just stay the hell out of the middle east. We can't just go in, take out ISIS and leave and expect there to be any ground gained. The middle east is a net loss shithole. It (not ISIS but what ISIS stands for... Shia/Sunni civil war that spans national borders) a problem the Middle East is going to have to solve for itself. This was always the problem in Iraq. There were Syrians and Saudis coming in to fight for Sunni groups and Iranians coming in to fight for Shia groups. They both fought the US and each other and have been doing this for decades before the US went in.
The fact we ignore the internal dynamics of the region is why we fail so miserably there. That's why one of the biggest stores of the last month or so, that Al Qaeda and ISIS are now essentially engaged in a war with each other, was lost in the American media. We take such a US centric view of the rest of the world that it renders us ignorant.