Why Boys Bully Other Boys
It has been established that boys bully other boys mainly for reasons related to power and control. A bully wants to mark his territory and make it known that he's the top dog in the classroom, in the grade level, or at the school. Power and domination are common themes in the pretend play of young children, and most young kids leave it in their pretend play world.
But some kids, the ones who become bullies, never seem to resolve this urge for power and domination. It might be because they feel powerless in an abusive home, they feel angry at being challenged in some way by life, or they may simply enjoy being the king of the hill.