Fight, Flight, Mimic is the first systematic study of deceptive mimicry in the context of wars. Deceptive mimicry -- the manipulation of individual or group identity -- includes passing off as a different individual, as a member of a group to which one does not belong, or, for a group, to 'sign' its action as another group. Mimicry exploits the reputation of the model it mimics to avoid capture (flight), to strike undetected at the enemy (fight), or to hide behind or besmirch the reputation of the model group ('false flag' operations). These tactics have previously been described anecdotally, mixed in with other ruses de guerre, but the authors show that mimicry is a distinct form of deception with its own logic and particularly consequential effects on those involved. The book offers a theory and game-theoretic model of mimicry, an overview of its use through history, and a deep empirical exploration of its modern manifestations through several case studies by leading social scientists. The chapters cover mimicry in the context of the Northern Ireland conflict, terrorism campaigns in 1970s Italy, the height of the Iraq insurgency, the Rwandan genocide, the Naxalite rebellion in India, and jihadi discussion forums on the Internet.