This article explores the hidden educational potential in the board game "Diplomacy." While commonly recognized as a good low-cost negotiation simulation and a useful teaching platform, the original game version over-emphasizes the conflictual nature of international relations and presents an image of international relations that is not reflective of the state of world politics today. The article reports experiences from developing and teaching a modified version of the game. It suggests a concrete way to integrate International Relations (IR) theories directly into the game. By making three common theoretical approaches an integrated part of the game, as well as expanding game strategies, win conditions and associated payoff tables, "Diplomacy" can be turned from a tool for teaching one variant of Realism into a flexible platform for teaching a broader range of IR theories, including Liberal-Institutionalism and Constructivism. In this way, the gap between abstract theory and simulated practice can be bridged in a way that students much appreciate as a learning mode. The article thus suggests a partial solution to one of the key challenges of using games and simulations in political science teaching: how to connect the game or simulation with theory.