Augustus Caesar came to power after assassinating the last of his rivals, Cleopatra and Mark Antony. He was the first Roman Emperor.
Augustus restored the Senate, modeled after the old Senate, with democratically elected magistrates, ensuring no single individual holds power.
Or so it seems. The Senate was only a ceremonial gesture. In reality, Augustus essentially declared himself the sole leader of Rome. Thus began a long line of emperors for the Roman Empire. Augustus also created a professional standing army from the citizen levy. He established regular pay and terms of service for the military, and created a pension for retiring veterans,