The one remaining combat zone in Iraq is the 26,000 square kilometer "Sunni Triangle" north and west of Baghdad. The Sunni Arabs, about 20 percent of Iraq's population, compose nearly all the population in this area. There are dozens of tribes in the area, and the tribal chiefs and their henchmen provide much of the government services (especially settling disputes.) Saddam and the Baath party always tried to work with the tribal chiefs, murdering those who refused to negotiate (and then offering to talk to the replacement chief.) The tribes always expected to get paid, to get a piece of any economic action in their area. For the tribes on the border, this meant some control over smuggling, or a cut of the customs duties on goods that were not smuggled (usually stuff to bulky or heavy to sneak across the border.) The oil wealth changed everything, and the tribes in the areas where the wells were had to share, or else. Saddam and Baath used this oil wealth to keep key people paid off. But most of the payroll went to Sunni chiefs. Kurds and Shias were offered much less money, or lots of bullets, bombs and poison gas if they made trouble.
Now the Kurds and Shias control the oil, and the Sunni tribes are not getting what they see as their fair share. Thus the attacks on oil fields and pipelines, but only where they run through the territory of Sunni tribes. The U.S. 4th Infantry Division controls most of the Sunni Triangle, and is playing hardball with those chiefs who refuse to cooperate. Chiefs, or key aides (including religious leaders), are arrested. Tribes that provide information on Baath Party leaders and illegal weapons supplies, get rewarded with jobs, and fewer patrols and raids. Thousands of Sunni Arabs have joined (or re-joined) the police force or work as government officials or translators. These are considered a major danger by Baath Party diehards and more of their attacks are shifting from American troops (who often fight back very effectively when ambushed) to Iraqis working with the Americans. It's obvious to Baath that more Iraqis are talking, because the American raids are snagging more Baath Party leaders (along with their cash and weapons stockpiles.) Over three dozen men suspected of attacking American troops have been arrested in the last two days. American interrogators have gotten a lot better in the last six months. They have had plenty of experience and every new captive yields new information, which leads to another raid and more arrests. American troops are increasingly turning guard duty over to Iraqi para-military troops (selected and trained by US troops) and concentrating on the raids.
The 4th Infantry Division intelligence people believe that Saddam Hussein is in their area of operations, and that eventually their growing network of informers will provide sufficient information to nail him. More senior Baath officials are being arrested, indicating that the informer network is working.