The Baiji refinery, with its distillation towers rising against the Hamrin Mountains, may be the most important industrial site in the Sunni Arab-dominated regions of Iraq. On a good day, 500 tanker trucks will leave the refinery filled with fuel with a street value of $10 million.
The sea of oil under Iraq is supposed to rebuild the nation, then make it prosper. But at least one-third, and possibly much more, of the fuel from Iraq's largest refinery here is diverted to the black market, according to American military officials. Tankers are hijacked, drivers are bribed, papers are forged and meters are manipulated -- and some of the earnings go to insurgents who are still killing more than 100 Iraqis a week.
"It's the money pit of the insurgency," said Capt. Joe Da Silva, who commands several platoons stationed at the refinery.
Five years after the war in Iraq began, the insurgency remains a lethal force. The steady flow of cash is one reason, even as the American troop buildup and the recruitment of former insurgents to American-backed militias have helped push the number of attacks down to 2005 levels.
In fact, money, far more than jihadist ideology, is a crucial motivation for a majority of Sunni insurgents, according to American officers in some Sunni provinces and other military officials in Iraq who have reviewed detainee surveys and other intelligence on the insurgency.
Although many American military officials and politicians -- and even the Iraqi public -- use the term Al Qaeda as a synonym for the insurgency, some American and Iraqi experts say they believe that the number of committed religious ideologues remains small. They say that insurgent groups raise and spend money autonomously for the most part, with little centralized coordination or direction.