The strategy of taking the ground and holding it have made some difference. But obviously the two largest factions, the Sunnis and the Sadr army, deciding not to fight made a much much larger difference.

Coincidental with the "surge" was the idea that the US would leave if things became peaceful. Remember the loss of Congress by the war party in 2006? The Iraqis could read the writing on the wall. To say the least it is difficult to sort out the influence of "the surge" from other factors. It is also impossible to claim that there has been any real progress until the militias have been disarmed.