Late one night in 556 B.C., King Nabonidus of Babylon saw the gods in a dream. He had just inherited a majestic but precarious birthright: the land between the Tigris and Euphrates rivers was an object of constant territorial dispute. Some part of it was always under siege, claimed by ancestral inhabitants or trod underfoot by roving warlords. The duty of the Šar Kiššati—the king of the world—was to impose his glorious order upon this chaotic landscape. That daunting assignment now fell to Nabonidus, in whom the gods naturally took an interest.

Turning to them in trepidation, Nabonidus complained of a fearsome menace that had lately disturbed the peace. The umman-manda, the “hordes from who-knows-where,” were stalking like blood-streaked ghosts through his kingdom. In Babylon’s Akkadian language, umman-manda was an all-purpose slur for any foreigner that threatened to destabilize the governing regime. In this case it was being lobbed at the Medes, whose swift horses carried them at alarming speeds from their base camps in the Zagros mountains to whatever city they chose to claim. But Marduk, king of gods, had a surprising revelation for Nabonidus: “That Mede you mentioned—he, his country, and the kings who march at his side shall be no more.” Nabonidus had this story written down on a fired clay cylinder and deposited