This essay investigates pre-battle omens and portents through three interpretative lenses: the ontological turn in anthropology, literary and historiographical criticism, and the cognitive science of religion. The Battle of Leuctra in 371 BC is used as a case study because Xenophon, Ephorus of Cyme, and Callisthenes of Olynthus recorded a uniquely large number of portents. Given that Leuctra fundamentally changed the balance of power in the Greek world, the various omens and portents described by our sources are fully consistent with the normative Greek worldview that signs were sent by the gods before important events. Scholars have been much more open to accepting that, despite some literary embellishment, the Greeks recognized omens retrospectively, but prospective omens are not improbable in a culture that was continually on the lookout for god-sent signs. The likelihood of prospective omens is confirmed by a comparative study of the omens that appeared to members of the Seventh Cavalry and to their Arikara scouts before the Battle of the Little Bighorn in 1876. We must avoid projecting a post-Enlightenment understanding of reality onto other cultures, thus devaluing the human dependence on communication with supernatural powers that was so central to the experience of the ancient Greeks.