It would send an unbelievably terrible signal to reformers across the region. It would say we've abandoned our desire to change the conditions that create terror. It would give the terrorists a safe haven from which to launch attacks. It would embolden Iran. It would embolden extremists. That's why we're not leaving Iraq.
Radical Islamists are serious about killing in pursuit of their extreme objectives. Releasing their soldiers can only embolden them to take more Americans hostage. The deal for Sgt. Bergdahl may well turn out to have been a bargain with the devil.
I think we all wear some kind of mask. There are masks that shield us from others, but there are masks that embolden us, and you see that in carnival. The shiest child puts on a mask and can do anything and be anybody.
A failed Iraq in the heart of the Middle East will provide safe haven for terrorists and extremists. It will embolden those who are trying to thwart the ambitions of reformers.