"The reinvention of decision making" Naturalistic Decision Making (NDM) provides a new approach for understanding and supporting decision makers as they work in complex, time-pressured, and high-risk environments. An NDM framework provides a perspective for understanding command decision making in complex organizations such as the Combined Joint Task Force and for supporting this decision making in a variety of operations including peace operations. This paper provides a detailed description of the field of NDM. The authors begin with a description of three different decision scenarios. These scenarios facilitate a discussion of the characteristics of naturalistic decision settings and the importance of expertise for naturalistic decision making. The authors conclude the chapter with discussions of research methods and the findings from NDM research that distinguish it from more traditional decision research.