Culture has enormous influence on military organizations. One can broadly define organizational culture as the assumptions, ideas, norms, and beliefs, expressed or reflected in symbols, rituals, myths, and practices, that shape how an organization functions and adapts to external stimuli and that give meaning to its members. Except in unique circumstances, culture grows slowly, embedding itself so deeply that members often act unconsciously according to its dictates. Because culture lies hidden under more visible organizational doctrine and symbols, one can easily overlook its power. Culture creates organizational identity and establishes expectations of how group members will act. Three important external factors impact military culture: geography, history, and the environment in which navies, armies, and air forces exist. Of all the factors involved in military effectiveness, culture is perhaps the most important. Yet it also remains the most difficult to understand, because it involves so many external factors that distort its formation and continuities, even in different military organizations within the same nation. Organizational culture will shape how military organizations respond to challenges. The hardship is that changing military culture represents an extraordinarily difficult task that may require years, if not decades, to accomplish.