No other ancient empire—not the Assyrian, not the Persian, not the Athenian— had succeeded on such a scale at holding together in harmony so many peoples, faiths, and traditions. Historians commonly describe these two centuries as the period of the Pax Romana (“the Roman Peace”), an age when a strong central government engineered and maintained the social stability that allowed people to prosper. The sheer vastness of the empire was astonishing: It stretched over three thousand miles from west to east, from the Strait of Gibraltar to the sources of the
Tigris and Euphrates rivers, and reached northward