AbstractIt is argued that a crucial element in decision-making in conflicts is the need for adequate conceptual complexity in problem formulation. This is illustrated by reference to a disastrous military failure—the fall of France in 1940. A formal model of the strategic situation is constructed using the Hypergame approach, in which the usual game-theoretic assumption that all "players" see the same "game" is discarded. Using this model, further features of the case are explored, and some general conclusions discussed. It is suggested that Hypergame analysis can be of assistance in achieving adequate levels of problem-perception in complex, conflict-prone environments, in particular by helping in the generation of multiple models.