Always I am Caesar

Ancient Rome casts a long shadow over the world. It is the empire against which other powers are compared, its story one of vast expansion and ultimate decline and fall, and a mix of apparently “modern” sophistication and utterly alien cruelty. These days only a minority of people have ever studied classics or ancient history, so the Roman Republic is today largely forgotten. For most, Rome means emperors—men draped in sheets and wearing laurel wreaths. A cartoonist can draw a modern politician—albeit probably only a male one—like this, and invoke decadence in general: Nero playing the fiddle or lyre while Rome burns.

In truth, Rome carved out an empire while it was still a republic, destroying Carthage in the process. Yet that is barely remembered. Jesus was born during the reign of Augustus, the future emperor Titus and his legions destroyed the Temple in...