Ruthless Liverpool produced a devastating display to march into the FA Cup semi-finals with their biggest win under manager Rafael Benitez and their biggest-ever away FA Cup victory.
Peter Crouch grabbed two goals in the first half, with a first-minute header from Sami Hyypia starting the rout at St Andrews.
Fernando Morientes, John Arne Riise – with a 25-yard cracker – an own goal from Olivier Tebily and a late effort from Djibril Cisse completed quarter-final humiliation for Birmingham in front of their own fans.