Sorry I've been on a bit of an Iraq war kick lately. I was on the streets protesting this war before it started in '03, and I've been involved in many antiwar efforts since.
Anyway, this graph from a recent GAO report shows the monthly number of attacks by insurgents in Iraq from the start of the war up until last August. Even a Republican (well, most of them anyway) could tell that this is not exactly indicative of a successful war effort.
(Click on image to get a larger version)