The Roman Republic was the phase of the ancient Roman civilization characterized by a republican form of government. The republican period began with the overthrow of the Monarchy c. 510 BC and lasted over 450 years until its subversion, through a series of civil wars, into the Principate form of government and the Imperial period. The precise event which signaled the transition of the Roman Republic into the Roman Empire is a matter of interpretation. Historians have variously proposed the appointment of Julius Caesar as perpetual dictator (44 BC), the Battle of Actium (2 September 31 BC), and the Roman Senate's grant of Octavian's extraordinary powers under the first settlement (January 16, 27 BC), as candidates for the defining pivotal event.