Ancient Egypt was ruled by pharaohs who served as both political and religious leaders. They made laws, collected taxes, and oversaw construction of temples. Egypt was divided into provinces governed by officials. In around 2400 BC, these governors grew too powerful and overthrew the pharaohs' rule, establishing their own armies and taxes. The Old Kingdom collapsed around 2150 BC during years of low flooding and reduced food production, destroying the power of the centralized kingdom. Egyptian society was strictly hierarchical, with slaves on bottom and pharaoh on top to maintain government organization.