BEIRUT -- Iraq's U.S.-trained military suffered a serious defeat on Sunday, chased out of the city of Ramadi by the Islamic militant group known as ISIS.
The U.N. says 25,000 civilians are fleeing the city of a half-million people, 70 miles west of Baghdad. It is the capital of a province once secured at the cost of 1,300 American lives.
It's the biggest military victory for ISIS since last summer, when the militant group swept Iraq's second-largest city of Mosul.
After four days of intense fighting, Iraqi authorities said that 500 people were left dead and thousands more fled as the black flag of ISIS was raised over Ramadi.
The fall of the city came in spite of intensified U.S. efforts to push back Islamic State fighters, with at least 180 airstrikes in the area over the last month.
AS ISIS militants flooded Ramadi, U.S.-trained Iraqi security forces appeared to flee. Policemen abandoned their stations, leaving behind their American-supplied weapons and equipment.
Ramadi is the largest city in the largely Sunni province of Anbar, which stretches from the western edge of Baghdad to Syria and Jordan.
Anbar was the heart of the insurgency against U.S. forces during the Iraq War, with nearly 1,300 Marines and soldiers killed there.
Last month, Iraq's prime minister promised a sweeping new military offensive in Anbar to root out ISIS militant. But with the retreat of Iraq's army, there are few appealing options.
Now the Iraqi government has mobilized its Shiite militias -- some supported by Iran-- to try and reverse its losses.
It's a controversial move: Many fear the presence of Shia paramilitary forces will reignite a religious war with Sunni residents and tribes.
The U.S. is also in an awkward position. The American military initially sat out the fight for Tikrit because the Shia militias which were fighting there.
Now, U.S. officials say that the militias have a part to play, if they operate under the control of the central Iraqi government.