Comparing Classical Empires

Sometime around 100 CE, a Roman merchant ship nudged against a dock in southern India, carrying Mediterranean wine and gold coins. At roughly the same moment, a Chinese envoy was traveling west along the Silk Road, bearing silk bolts and diplomatic credentials from the Han court. Neither man had any real understanding of the other's empire. They knew the other existed — the Romans called China Serica, "the land of silk"; the Chinese called Rome Daqin, "the great Qin" — but the details were mostly rumor and fantasy.

If those two men had somehow sat down and compared notes, they would have found that their empires, separated by five thousand miles of steppe and desert, had arrived at strikingly similar solutions to strikingly similar problems. Both had built professional armies. Both had developed sophisticated tax systems. Both maintained vast road networks. Both struggled with the same question: how to hold together a territory so large that a message from the capital could take weeks to reach the frontier.

The classical world produced four imperial systems that, between them, governed the majority of the human population on the Eurasian landmass. Each arose from different circumstances, in different geographies, among peoples with different languages, religions, and cultural assumptions. Yet each had to answer the same question: how do you rule millions of people spread across thousands of miles when the fastest communication technology is a horse?