Sunnis moved out right before troop surge because of ethnic cleansing,

[Realitycheck]

hence less violence.

 

 

http://news.yahoo.com/s/nm/20080919/sc_nm/iraq_lights_dc_2

[Pangloss]

As I understand it, they came back to their neighborhoods, but the violence has not returned at this point in time. But yes, we've already agreed here that the Surge was not by itself responsible for the decrease in violence, though it was a major (arguably the major) factor.