Transcending ethnic, linguistic, and religious boundaries, early empires shaped thousands of years of world history. Yet despite the global prominence of empire, individual cases are often studied in isolation. This series seeks to change the terms of the debate by promoting cross-cultural, comparative, and transdisciplinary perspectives on imperial state formation prior to the European colonial expansion.

Two thousand years ago, up to one-half of the human species was contained within two political systems, the Roman empire in western Eurasia (centered on the Mediterranean Sea) and the...