The last and longest war of classical antiquity was fought in the early seventh century. It was ideologically charged and fought along the full length of the Persian-Roman frontier, drawing in all the available resources and great powers of the steppe world. The conflict raged on an unprecedented scale, and its end brought the classical phase of history to a close. Despite all this, it has left a conspicuous gap in the history of warfare. This book aims to finally fill that gap.