Ancient Greek history, if we define it as the history of people speaking some form of the Greek language and living on the Greek mainland, begins with Mycenean culture. What we can reconstruct from oral tradition and archeology suggests that mainland Greece consisted of several kingdoms, each run by a leader known as a "wanax". There is evidence that although various mainland kingdoms may have cooperated on occasion, there was no unified Greek "nation" but instead various small kingdoms existing in relationships of temporary truce and ongoing conflict. The Mycenean culture ended (reasons are still unclear, civil war and invasions may both have contributed) in approximately the 13th century, to be replaced by independent cities led by kings or groups of nobles in the "geometric period". In the archaic and classical periods, Greece was divided into city-states or "poleis" with political structures varying from democratic to monarchical to oligarchic. The conquests of Philip, Alexander, and subsequently the Romans, led to Greece becoming part of larger empires, a political structure that lasted until Greek independence in the 19th century.