Bobo and various other neocons have been on a crusade to get liberals to “admit that the surge worked”. This is part of a larger effort to rehabilitate George W. Bush, the Iraq War, and neoconservatism.
Of course, there’s no doubt that violence did start to go down a great deal in Iraq about six months after the so-call surge began in Iraq. Bob Woodward (here; here) attributes this to strategic operational changes that had little to do with having more troops there. Juan Cole thinks that ethnic cleansing — of Badhdad Sunnis by Baghdad Shiites — played a large role.
Maybe it’s impossible to know for certain, but it seems very unlikely to me that a small increase, percentage-wise, in the number of troops in Iraq could have caused the decrease in violence. But maybe that’s because I hate freedom.