The backing of the regime by ancient clans is a relatively recent development, stemming from the aftermath of the 1991 Gulf War, a time in which Saddam was weakened at home.

The Iraqi leader turned to the tribes to help reinforce his slackened grip on power, according to Iraqi opposition members in exile.

The tribes were highly influential under the monarchy that ruled the country until 1958 but were brushed aside by the Baath Party which succeeded it and considered their customs backward and primitive.

But the first Gulf War changed everything by loosening the state command structure, leaving Saddam scrambling to shore up his domestic support.

Paradoxically, the international embargo slapped on the country after Iraq invaded Kuwait, aimed at undermining Saddam, ended up offering him a golden opportunity to re-establish his control over an increasingly impoverished society.

Faleh Jabber, a researcher at the School of Politics and Sociology at the University of London-Birkbeck, noted in a recent article that the food supply increasingly depended on Saddam’s good will, and on the tribes.

One of the consequences of the sanctions was also to make the tribes more dependent on government support.

To foster a reconciliation and establish himself as chief of the chiefs, Saddam invited tribal leaders to one of his palaces in 1992. He apologized for new land reforms that stripped them of resources and called for a rapprochement. In effect, he bought their allegiance by offering food, vital materials, money and in particular, the opportunity for them to exercise new influence.

The tribes were able to run their areas like fiefdoms, all the while working as cogs of the state. They were given authority over security, police forces, the justice system and tax collection and the scope to operate beyond their traditional areas of control into major cities including Baghdad.

Exempted from military service, the men of the tribes received light arms and means of transportation and communication to allow them to help Saddam Hussein crush any domestic unrest.

The government saw the utility of their support in 1991 when they assisted him in stamping out a rebellion in south of the country, which has a Shiite majority.

The ties binding the tribes to Saddam Hussein and their willingness to protect the status quo that operates in their favor are among the factors leading the tribes to oppose the current US-British invasion.

Aware that they could represent a secret weapon against the Americans, Saddam yesterday called on all Iraqis and the tribes in particular to continue to resist the enemy and congratulated them on their success in slowing the coalition advance.

“Even in the open desert, American and British soldiers are exposing themselves to civilians’ weapons,” he said.

Iraqi television showed images of a US Apache helicopter that had been shot down over Kerbala, 80 km (50 miles) south of Baghdad. Ali Obeid, an old peasant with a white beard and brandishing an elderly bolt-action rifle, proudly told the cameras that he had downed a second aircraft of the same type.