The Roman emperors were the rulers of the Roman Empire dating from the granting of the title of to Gaius Julius Caesar Octavianus by the Roman Senate in 27 BC, after major roles played by the populist dictator and military leader Julius Caesar. Augustus maintained a facade of Republican rule, rejecting monarchical titles but calling himself (first man of the council) and (first citizen of the state). The title of Augustus was conferred on his successors to the imperial position. The style of government instituted by Augustus is called the Principate and continued until reforms by Diocletian. The modern word 'emperor' derives from the title , which was granted by an army to a successful general; during the initial phase of the empire, the title was generally used only by the . For example, Augustus' official name was "Imperator Caesar Divi Filius Augustus".