The fighting with the Baath Party resistance is causing the coalition forces about six casualties a day. The Baath has managed to organize a loose coalition of Baath members, Iraqi Islamic conservatives (which the Baath has been supporting for the last ten years), al Qaeda followers and Arab nationalists. All these groups are comprised mainly of Sunni Arabs. In Iraq, the Sunni Arabs have always been opposed by Shia Arabs and Kurds (who are Sunni, but ethnically related to Iranians.) What is going on in Iraq is a continuation of the civil war between the Sunni Arabs and the other groups (who are 80 percent of the population), with coalition troops doing most of the fighting. The coalition prefers it that way, for the alternative is Shia, Kurd and Sunni Arab militias fighting it out.
Defeating the Sunni Arabs and its Baath Party organization won't be easy, for many Sunni Arabs have a major incentive to resist. They realize that once a democratic vote is held, the Shia will be in charge and they will proceed to insure that Shia get the economic benefits long monopolized by the Sunni Arabs. By attacking rebuilding efforts and oil production, Baath believes it can trigger an uprising by Shia militias, increased fighting throughout the country and eventual withdrawal of coalition forces. In a civil war, Baath could take over again. Now if this sounds far fetched, it's not much different than any of the other schemes Baath has gotten behind over the past half century.
Rooting out the Baath Party is rather more difficult than was eliminating Nazi Party influence in post-World War II Germany. Nazi party membership was not based on an ethnic and religious group as the Baath Party is, and the Nazis were thoroughly discredited politically and militarily, after World War II. But many European nations (France, Germany, Russia) would be happier if Baath (with a kinder, gentler, leader) were back in charge (and willing to honor French and Russian contracts and debts.) Baath does not see the 2003 war as a defeat, but a setback.
The Sunni Arabs will never fully accept democratic rule in Iraq, but a year or so of police work to round up the most active Baath Party leaders, and seizing most of the money and weapons Baath still holds in Iraq, will reduce Baath to the status of one of the many criminal gangs that have always made life miserable in the Baghdad area.
Most of Iraq is quiet, but the Sunni Arab areas, especially in the western suburbs of Baghdad, are the scene of most of the ambushes and attacks on coalition patrols and convoys.