The process of foreign policy decision making is influenced in large part by beliefs, along with the strategic interaction between actors engendered by their decisions and the resulting political outcomes. In this context, beliefs encompass three kinds of effects: the mirroring effects associated with the decision making situation, the steering effects that arise from this situation, and the learning effects of feedback. These effects are modeled using operational code analysis, although “operational code theory” more accurately describes an alliance of attribution and schema theories from psychology and game theory from economics applied to the domain of politics. This “theory complex” specifies belief-based solutions to the puzzles posed by diagnostic, decision making, and learning processes in world politics. The major social and intellectual dimensions of operational code theory can be traced to Nathan Leites’s seminal research on the Bolshevik operational code, The Operational Code of the Politburo. In the last half of the twentieth century, applications of operational code analysis have emphasized different cognitive, emotional, and motivational mechanisms as intellectual dimensions in explaining foreign policy decisions. The literature on operational code theory may be divided into four general waves of research: idiographic-interpretive studies, nomothetic-typological studies, quantitative-statistical studies, and formal modeling studies. The present trajectory of studies on operational code points to a number of important trends that straddle political psychology and game theory. For example, the psychological processes of mirroring, steering, and learning associated with operational code analysis have the potential to enrich our understanding of game-theoretic models of strategic interaction.