Ahriman: it was the state religion. Missionary monks had been roaming west from Afghanistan, teaching Buddhism, but the seeds they dropped would not grow in the soil of Zoroastrian Persia, so they turned east, which is why Buddhism spread to China but not Europe. Countless Persian tales and legends of later times go back to this Sassanid period. The greatest of the Sassanid kings, KhusrowAnushervan, came to be remembered (by Persian speakers) as the archetype of the “just king,” conflated perhaps with Kay Khosrow, the third king of Iran’s mythical first dynasty, something like an Arthurian figure presiding over a Persian Camelot and served by noble warriors. 3
The Roman Empire, meanwhile, was falling apart. In 293, the emperor Diocletian divided the empire in four parts for administrative purposes: it had grown just too huge and cumbersome to run from a single center. But Diocletian’s reform ended up splitting the empire in two. The wealth was all in the east, it turned out, so the western part of the Roman Empire crumbled. As nomadic German tribes moved into the empire, government services shrank, law and order broke down, and trade decayed. Schoolsfoundered, western Europeans stopped reading or writing much, and Europe sank into its so-called Dark Ages. Roman cities in places like Germany and France and Britain fell into ruin, and society simplified down to serfs, warriors, and priests. The only institution binding disparate locales together was Christianity, anchored by the bishop of Rome, soon known as the pope.
The eastern portion of the Roman Empire, headquartered in Constantinople, continued to hang on. The locals still called this entity Rome but to later historians it looked like something new, so retrospectively they gave it a new name: the Byzantine Empire.
Orthodox Christianity was centered here. Unlike Western Christianity, this church had no pope-like figure. Each city with a sizable Christian population had its own top bishop, a “metropolitan,” and all the metropolitans were supposedly equal, although the top bishop of Constantinople was more equal than most. Above them all, however, stood the emperor. Western learning, technology, and intellectual activity contracted to Byzantium. Here, writers and artists continued to produce books, paintings, and other works, yet once eastern Rome became the Byzantine Empire it more or less passed out of Western history.
Many will dispute this statement—the Byzantine Empire was Christian, after all. Its subjects spoke Greek, and its philosophers . . . well, let us not speak too much about its philosophers. Almost any well-educated Westerner knows of Socrates, Plato, and Aristotle, not to mention Sophocles, Virgil, Tacitus, Pericles, Alexander of Macedon, Julius Caesar, Augustus, and many others; but apart from academics who specialize in Byzantine history, few can name three Byzantine philosophers, or two Byzantine poets, or one Byzantine emperor after Justinian. The Byzantine Empire lasted almost a thousand years, by few can name five events that took place in the empire during all that time.
Compared to ancient Rome, the Byzantine Empire didn’t wield much clout, but in its own region it was a superpower, largely because it had no competition and because its walled capital of Constantinople was probably the most impregnable city the world had ever known. By the mid-sixth century, the Byzantines ruled most of Asia Minor and some of what we now call eastern Europe. They butted right up against Sassanid Persia, the region’s other superpower. The Sassanids ruled a swath of land stretching east to the foothills of the Himalayas. Between the two empires lay a strip of disputed territory, the lands along the Mediterranean shore, where the two world histories overlap and where disputes have been endemic. To the south, in the shadow of both big empires, lay the Arabian Peninsula, inhabited by numerous autonomous tribes. Such was the political configuration of