Descriptions of battles in ancient authors are not mirrors of reality, however dim and badly cracked, but are a form of literary production in which the real events depicted are filtered through the literary, intellectual, and cultural assumptions of the author. By comparing the battle descriptions of Julius Caesar to those of Xenophon and Polybius this paper attempts to place those battle descriptions in their intellectual and cultural context. Here Caesar appears as a military intellectual engaged in controversies with experts in the Greek tradition of military theory-rejecting materialist strains of Greek thinking-and also as a Roman soldier whose military experience and cultural conceptions about how battles work could not be fully accommodated by Greek models. Caesar adapts from the Greeks an intellectual model of tactics based on physical metaphors, but adjusts Greek theory to Roman experience: Caesar's tactical physics ramifies from the crash-impetus-of the legionary charge rather than the push of the phalanx. Caesar also adapts from the Greeks a simplifying model of military psychology, adjusting a Greek binary scheme of morale into a three-level model to accommodate a Roman military ethos of steadiness in combat. Greek military thinking downplayed the role in battle of innate differences in courage between armies or nations, concentrating instead on tactics and stratagems; Roman culture encouraged Caesar to reject this dismissive view and elaborate a detailed understanding of the role of courage-virtus-in the mechanics of battle. The prominence of virtus in Caesar's battle descriptions illustrates its survival as an important Roman cultural norm and tempts speculation as to its historical consequences. Attempts to reconstruct ancient battles must take into account the cultural and intellectual traditions which guide ancient battle descriptions.