This article compares the explanatory power of five mainstream theories from International Relations, political science and public management in understanding why – when they are engaged in deepening conflict and tension and even preparations for wars – states might simultaneously sustain deepening cooperation in global regulatory bodies. Analysis of explanatory power focuses on trade-offs among five key methodological virtues, and on buffering as an indicator of state unitariness. The theories are examined against the crucial case of one state’s commitment to the first international regulatory regime, the International Telegraph Union (ITU) and the Submarine Cable Convention (SCC) of 1884, from the founding of the ITU in 1865 to the outbreak of the Great War. In this article, we use UK National Archives files to reconstruct Britain’s decisions in telegraphy policy as our case of a state’s decision-making. We focus on four key clusters of decisions, spanning three sub-periods. The study finds each of the theories can descriptively capture some developments in some sub-periods, but not for the reasons identified in the theory and without generality of application. It therefore provides the basis for future theoretical development work and demonstrates the value of theory comparison by analysis of trade-offs among methodological virtues.