This article asks when, how, and why states started to use the concept of international community in the shared language of diplomacy and international law. It argues that the concept was accepted to the interstate language as a result of debates over international institutions, which were to acquire a universal character, at the Hague Conferences of 1899 and 1907. The article suggests that conceptual changes in interstate language should be understood as products of rhetorical power struggles, in which some arguments lose the battle while others prevail, some concepts are discarded while others modified. The article suggests a model of conceptual change that explains an innovation in interstate language. First, it draws attention to collective assertive speech acts at diplomatic events that signal changes in international politics. Second, it examines whether such acts implicate conceptual innovations. Third, it posits that the composition of epistemic community assembled at the Hague determines the nature of conceptual innovation. Fourth, it demonstrates how rhetorical interventions into debates at the conference introduce and mould relevant concepts. Fifth, it illuminates how contextualisation of the conference interventions in professional debates helps us understand the polemical nature of arguments and the scope of conceptual innovation.