What influences decision-makers to attack another country when on the brink of war? The main aim of this study is to detect a causal mechanism underlying the decision to attack another country when... Show moreWhat influences decision-makers to attack another country when on the brink of war? The main aim of this study is to detect a causal mechanism underlying the decision to attack another country when on the brink of war, and whether or not this mechanism differs between regime-types. It investigates whether or not regime-type, the nature of the conflict, the power used, and hawkish beliefs of decision-makers matter in this decision. By addressing this question from a political psychological and comparative perspective, this dissertation tests the microfoundations of democratic peace theory simultaneously with alternative theories of decision-making during conflict resolution.The core analytical instrument is a decision-making experiment, executed in the US, Russia, and China. The experimental results are triangulated with a large N-study, and a case study. The overall results show that although the democratic peace as an empirical regularity might still be valid, the theoretical arguments to explain why democracies do not fight with each other turn out to be built on empirically unsupported foundations. This study argues that an actor-based approach towards decision-making processes within international relations offers important insights to the more structured-based theories of international relations. It thereby convincingly shows that the individual matters, also in IR. Show less