Step back a pace, and that's actually good news.

The bottom line is to be in a situation where pulling out the ocuupation forces from Iraq does not lead to a bloody civil war, and this kind of incident is actually helpful in getting there.

The essential thing is to avoid thinking in terms of military victory and so forth. That just lead to a continuing and escalating war going on for years, which will end badly. Unfortunately those are the terms, pretty clearly, in which the people in charge do think.