Ancient Egypt was ruled by pharaohs who served as both political and religious leaders. They collected taxes, performed rituals, and oversaw construction projects. The country was divided into provinces governed by officials. In around 2400 BC, these governors grew too powerful and overthrew the pharaohs' authority, establishing their own armies and taxes. The Old Kingdom collapsed around 2150 BC after several years of low flooding caused food shortages. Egyptian society was strictly hierarchical, with slaves on bottom and pharaoh on top.