What is going to happen now in Iraq,when the U.S. attacks Sadr?

U.S. is attacking Shiite Militia and Sadr now that Saddam is dead. What will happen?.Is Bush focusing on personalities he doesn't like?They say it is in general against all the insurgents but the Kurdish Peshmergas in Baghdad will definitely have no problem attacking the Shiites.Anybody who has been there please answer.