From Versailles to the Kellogg-Briand Pact: Prohibiting and Justifying Aggression in the Interbellum

The article is a historical re-description of international legal debates concerning the ius ad bellum in the Interwar period (1919–1936). Using a core/periphery heuristic, it is demonstrated that the normative changes created by the League Covenant and the Kellogg-Briand Pact were being drafted and interpreted by the great powers in a way that still allowed them to justify military interventions in their peripheries. Even military violence between Western states could only be partially outlawed by these instruments. Legal uncertainties produced during the drafting of the new instruments could readily be exploited by the Western dominated international legal discourse. And yet, with the principle of sovereign equality on the rise in the Interbellum, and the battle of semi-periphery governments against the ‘standard of civilisation', traditional justifications for military violence came under increasing pressure. At that very moment, international lawyers in the core introduced a broader understanding of self-defence, gradually replacing former justifications for military interventions both within the core and in the peripheries of Western powers. All of this taken together in practice arguably consumed a substantial part of the alleged ‘progress' made by international legal pacifism in the Interbellum