The following is meant to provide an overview of the military situation in Iraq for non-experts.
Link:http://www.brookings.edu/blogs/up-fr...xm5MgY.twitter

Very good explanation and the caveat is well worth it too:
Caveat. It is exceptionally difficult to understand the dynamics of ongoing military operations. Oftentimes, the participants themselves do not know why they are winning or losing, or even where they are in control or where their troops are. For non-participants, it is often equally difficult to gain more than a rudimentary sense of the combat without access to the sophisticated intelligence gathering capabilities—overhead imagery, signals intercepts, human reporting, etc.—available to the United States and some other governments. As one of the CIA’s Persian Gulf military analysts during the 1990-91 Gulf War, I noted the difficulty that many outside analysts had in gauging the capabilities of the two sides and following the course of operations because they did not have access to the information available to us from U.S. government assets. Consequently, readers should bring a healthy dose of skepticism to all such analyses of the current fighting in Iraq, including this one.