Is military incompetence adaptive?

Military engagements are categorized as raids or battles, according to whet her one or both sides has the opportunity to assess the other. In raids, as sessment appears to be accurate. This means that aggressors experience low costs, which allows violence to be adaptive. A commonly reported reason for battles, by contrast, is a failure of assessment: both opponents hold posi tive illusions and believe they will win. This article asks why this form o f battle incompetence occurs, Explanations in terms of individual anomaly o r cognitive constraints appear unsatisfactory. Here, I propose two mechanis ms by which positive illusions tend to promote victory. First, according to the Performance Enhancement Hypothesis, they suppress negative thoughts or feelings, This applies to both raids and battles. Second, the Opponent-Dec eption Hypothesis suggests that positive illusions increase the probability of a successful bluff, This applies only to battles. Military incompetence is proposed to be the result of adaptive strategies of self-deception, whi ch unfortunately promote an increased intensity of violence. (C) 1999 Elsev ier Science Inc.