This thesis explores the determinants of command structure centralization in military coalitions between 1848 and 2003. Coalitions are a common, and often successful, occurrence in warfare. Establishing a chain of command in coalitions is, however, paradoxical. While a strongly centralized multinational chain of command is considered effective, nations are reluctant to relinquish the operational control of their armed forces. This thesis aims to answer which factors decide if a coalition is strongly or weakly centralised. A quantitative dataset of 35 wartime coalitions is employed in a multiple linear regression, where common aims, democracy, regime type homogeneity, presence of predominant actors, and prior defensive alliances are examined as possible determinants. The analysis finds that democratically homogeneous coalitions are associated with centralized command structures. However, when the dataset is limited to post-1945 coalitions, all proposed determinants – except prior alliances – are statistically significant. These findings suggest that the structure of coalitions is shaped, in part, by their members’ regime characteristics, but also emphasize a difficulty in studying coalitions without accounting for the specific international system in which they exist.