 By 48 BC , after having defeated the last of his major enemies , Julius Caesar wanted to ensure that his control over the government was undisputed . He assumed these powers by increasing his own authority , and by decreasing the authority of Rome 's other political institutions . Caesar held the office of Roman Dictator , and alternated between the Consulship ( the chief @-@ magistracy ) and the <unk> ( in effect , a military governorship ) . In 48 BC , Caesar was given the powers of a Plebeian Tribune , which made his person sacrosanct , gave him the power to veto the Senate , and allowed him to dominate the legislative process . After Caesar was assassinated in 44 BC , Mark Antony formed an alliance with Caesar 's adopted son and great @-@ nephew , Gaius Octavian . Along with Marcus Aemilius Lepidus , they formed an alliance known as the Second Triumvirate , and held powers that were nearly identical to the powers that Caesar had held under his constitution . While the conspirators who had assassinated Caesar were defeated at the Battle of Philippi in 42 BC , the peace that resulted was only temporary . Antony and Octavian fought against each other in one last battle in 31 BC . Antony was defeated , and in 30 BC he committed suicide . In 29 BC , Octavian returned to Rome as the unchallenged master of the state . The reign of Octavian , whom history remembers as Augustus , the first Roman Emperor , marked the dividing line between the Roman Republic and the Roman Empire . By the time this process was complete , Rome had completed its transition from a city @-@ state with a network of dependencies , to the capital of an empire . 
