At the top of the list is a very obvious choice – the founder of the Roman Empire himself, Augustus, who has the longest reign of 41 years from 27 BC to 14 AD.
The reign of Augustus initiated an era of relative peace that was known as Pax Romana or the Roman Peace. Yes, there were several wars at the Roman frontiers in the name of expansion and a year-long civil war too, but after the succession of Augustus to the throne, the Roman world was free of any large-scale warfare for more than two centuries.
