Though its archaeological record stretches back tens of thousands of years, Italian history begins with the Etruscans, an ancient civilization that rose between the Arno and Tiber rivers. The Etruscans were supplanted in the 3rd century bce by the Romans, who soon became the chief power in the Mediterranean world and whose empire stretched from India to Scotland by the 2nd century ce. That empire was rarely secure, not only because of the unwillingness of conquered peoples to stay conquered but also because of power struggles between competing Roman political factions, military leaders, families, ethnic groups, and religions.