Romans overran Syria, Macedonia, Greece and Egypt, all of which had until then been part of the decaying Hellenistic empire created by Alexander the Great. But such expansion was not without costs; tensions grew and civil war erupted. The ensuing period of unrest and revolution marked the transition of Rome from a republic to an empire. The later stages of these civil wars encompassed the careers of the brilliant Pompey, the orator Cicero, and the consul Julius Caesar, the conqueror of Gaul (58-50 BC), who eventually was given power over Rome as its dictator. After his assassination in 44 BC, it was not long before civil war again erupted; but following his victory at Actium (31 BC), Octavian, Julius' nephew, was crowned Rome's first emperor, Augustus 27 BC-14 AD). Although there were exceptions such as Caligula (37-41) and Nero (54-68), Rome was blessed with a series of able and brilliant leaders who expanded the frontiers until Rome's empire reached from Britain to Egypt and from Spain to Persia. Imperial Rome was distinguished not only for its military - the foundation upon which the empire rested - but also for its accomplishments in engineering and statecraft. The Romans were gifted in the applied arts of law, record-keeping and city planning, yet they also acknowledged and adopted the contributions of earlier peoples - most notably, those of the Greeks, much of whose culture was thereby preserved. Roman law was a complex body of precedents and opinions, which were finally codified in the 6th century as the Justinian Code. The empire's road network was without match in the ancient world, designed for rapid movement of commerce, agriculture, mail delivery as well as the army. Roman city planners achieved unprecedented standards of hygiene with their plumbing, sewage disposal, dams and aqueducts. Roman art and architecture, though often imitative of Greek styles, was boldly planned and lavishly executed. Roman science and culture, in short, became the foundations of the European world.