When the father of military history penned those words in 431 BC, he introduced a question about the practical utility of historical inquiry that reverberates to the present day: How and to what extent can the study of history usefully inform the man of affairs? The question is especially acute for the professional soldier, for whom the opportunity to practice his or her profession happily is episodic. Unlike other human enterprises in which constant repetition allows for a smooth learning curve, war generally occurs at intervals sufficiently great, and in circumstances so diverse and unrepeatable, that military organizations cannot take for granted the useful transfer of experience from one conflict to the next.

Indeed, despite the conventional accusation that militaries invariably prepare to refight the last war, closer examination suggests they are prone more often to ignore history, or at best recall it carelessly, if not disingenuously. That has been the more true during the past half-century of rapid technological change, during which the recurring tendency has been to discount the relevance of the past altogether.