Harold Guetzkow's guidance of research on foreign policy decision making was driven by a core concern: the avoidance of nuclear war and preservation of peace. He aimed to do this by supporting the creation and distribution of new knowledge through experiments aimed at simulating the processes and conditions hypothesized to influence such decisions. This article outlines the progress of his simulation design efforts and their transformations under many whom he mentored as research assistants in this work. It also touches on his beliefs.