Contrary to what John McCain was screeching about yesterday, the reduction in Iraqi sectarian violence wasn't really the consequence of our military escalation there. Robert Parry wrote an excellent takedown of the myth, beginning with the salient point:
...the “surge” sacrificed some 1,000 additional U.S. military dead (and killed countless innocent Iraqis) while contributing very little to the war’s outcome.
Any serious analysis of what happened in Iraq in 2007-08 would trace the decline in Iraqi sectarian violence mostly to strategies that predated the “surge” and were implemented by the U.S. commanding generals in 2006, George Casey and John Abizaid, who wanted as small a U.S. “footprint” as possible to tamp down Iraqi nationalism.