I characterize violence as falling into two types, using Arthur Koestler's two tendencies: integrative and self-assertive. It is the integrative tendency, the belief in a cause and the abrogation of one's identity and obedience to a higher authority, that leads to integrative violence and wars. The principal cause of violence is not individual aggressiveness, but submission to ingroup, cause, ideology, or country. Simulation/games and debriefing protocols need to take into account a wide spectrum of research on the springs of violence if they are to promote durable peace.