Throughout history, people have seemingly been embroiled almost constantly in violence, conﬂict, and war. And, for an equally long period of time, writers from numerous disciplines have sought to understand the causes of such strife (Brown, 1987; Nieburg, 1969). Although a discussion of this subject could reasonably be seen to require a review of the voluminous research into violence and aggression that has been conducted in psychology and sociology, this is really beyond the limited scope of this chapter. In fact, much of this literature is already discussed in our other chapters dealing with ethnic nationalism, violence, and genocide. Instead, this chapter seeks to use international security and conﬂict as an example in order to illustrate how political psychological approaches have been applied by political scientists to better understand such problems as the causes of war, the security dilemma, and deterrence. In doing so, it is hoped that students will better appreciate how psychological concepts can be usefully applied to real-world political problems. The portions of the Political Being focused upon in this chapter are cognition, emotion, and perceptions of them.