From Informed Comment

Myth: The US troop surge stopped the civil war that had been raging between Sunni Arabs and Shiites in the Iraqi capital of Baghdad.
The civil war in Baghdad escalated during the US troop escalation. Between January, 2007, and July, 2007, Baghdad went from 65% Shiite to 75% Shiite. UN polling among Iraqi refugees in Syria suggests that 78% are from Baghdad and that nearly a million refugees relocated to Syria from Iraq in 2007 alone. This data suggests that over 700,000 residents of Baghdad have fled this city of 6 million during the US 'surge,' or more than 10 percent of the capital's popula...

From Informed Comment

Myth: The US troop surge stopped the civil war that had been raging between Sunni Arabs and Shiites in the Iraqi capital of Baghdad.
The civil war in Baghdad escalated during the US troop escalation. Between January, 2007, and July, 2007, Baghdad went from 65% Shiite to 75% Shiite. UN polling among Iraqi refugees in Syria suggests that 78% are from Baghdad and that nearly a million refugees relocated to Syria from Iraq in 2007 alone. This data suggests that over 700,000 residents of Baghdad have fled this city of 6 million during the US 'surge,' or more than 10 percent of the capital's population. Among the primary effects of the 'surge' has been to turn Baghdad into an overwhelmingly Shiite city and to displace hundreds of thousands of Iraqis from the capital.
Myth: The reduction in violence in Iraq is mostly because of the escalation in the number of US troops, or "surge."
Fact: Although violence has been reduced in Iraq, much of the reduction did not take place because of US troop activity. Guerrilla attacks in al-Anbar Province were reduced from 400 a week to 100 a week between July, 2006 and July, 2007. But there was no significant US troop escalation in al-Anbar. Likewise, attacks on British troops in Basra have declined precipitously since they were moved out to the airport away from population centers. But this change had nothing to do with US troops.