RAMADI, Iraq - Not long ago it would have been unthinkable: a Sunni sheik allying himself publicly with American forces in a xenophobic city at the epicenter of Iraq's Sunni insurgency.

Today, there is no mistaking whose side Sheik Abdul Sattar al-Rishawi is on. Outside his walled home, a U.S. tank is on permanent guard beside a clutch of towering date palms and a protective dirt berm.

The 36-year-old sheik is leading a growing movement of Sunni tribesmen who have turned against al-Qaida-linked insurgents in Anbar province. The dramatic shift in alliances may have done more in a few months to ease daily street battles and undercut the insurgency here than American forces have achieved in years with arms.

The American commander responsible for Ramadi, Col. John W. Charlton, said the newly friendly sheiks, combined with an aggressive counterinsurgency strategy and the presence of thousands of new Sunni police on the streets, have helped cut attacks in the city by half in recent months.

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Al-Rishawi, whose father and three brothers were killed by al-Qaida assassins, said insurgents were "killing innocent people, anyone suspected of opposing them. They brought us nothing but destruction and we finally said, enough is enough."

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But violence in some districts of Ramadi previously hit by daily street battles has dwindled to a degree so low that American soldiers can walk on the streets in some areas and hand out soccer balls without provoking a firefight — apparently a direct result of the sheik's influence.

U.S. Lt. Nathan Strickland, also of the 1-77th, said the sheiks were influenced by the realization that Shiite Iran's regional influence was rising, and "the presence of (Sunni) foreign fighters here was disrupting the traditional local tribal structure."

Al-Rishawi and other sheiks urged their tribesmen to join the police force, and 4,500 Sunnis heeded the call in Ramadi alone — a remarkable feat in a city that had almost no police a year ago...