This chapter examines the origin of the customary prohibition of the use of force between States and its relationship to article 2(4) of the UN Charter, focusing on the pre-UN Charter era. In doing so, it critically analyses two possibilities for the norm to have emerged prior to 1945: that it developed prior to the UN Charter and article 2(4) was declaratory of that pre-existing custom, or that article 2(4) crystallised a customary rule that was already in the process of formation. It rejects these two possibilities, arguing that article 2(4) was a significant legal development which went beyond the existing laws of the time in order to found a new international legal order in the aftermath of World War II. Any pre-existing customary limitations on the use of force were significantly broadened by article 2(4), and the drafting process was not accompanied by meaningful State practice developing in parallel with this radical change in the law. Therefore, the customary rule prohibiting recourse to force between States must have arisen after the Charter entered into force. The emergence and development of the customary rule from 1945 onwards are examined in the next chapter.

Today, Sheffield’s East End is mostly gone. Its streets and terraced houses have been demolished. The men, women and children who populated its soot-blackened neighbourhoods, huddled beneath the looming, thundering steelworks, have been scattered to newer housing developments. The seemingly endless landscape of steelworks and coal pits has also been consigned to memory. While the steel makers Forgemasters and Outokumpu remain, the land surrounding them has been cleared of their illustrious forebears and no longer teems with their workers. Light industries, retail parks and leisure outlets have taken their place. Attercliffe Road, once the main artery of a proudly self-contained district boasting its own schools, churches, pubs and even a department store, now accommodates little to please the eye of the passing observer. The constant bustle of thousands of workers maintaining a twenty-four-hour, three-shift system no longer fills the air with the clanging of trams, the clatter of bicycles and the scrape of hobnail boots on flagstones.

The first half of the twentieth century is often characterised as a period of economic, political and moral collapse among European nations. Widespread ultra-nationalism, racist and eugenic theories, anti-Semitism, imperialism and world war are all closely and inseparably linked with the period. The rise of fascism across Europe had its British analogue in the Blackshirts of Sir Oswald Mosley’s British Union of Fascists, notorious for organising and marching for a ‘Greater Britain’ and in defence of the Empire, within working-class districts.1 Indeed the sporadic rioting and disorder which accompanied the Blackshirts’ attempt to march through London’s East End, together with the race riots that took place in a number of British ports in the immediate aftermath of the First World War, are viewed as symptomatic of the febrile atmosphere of racial tension during the inter-war period in Britain. ‘Hitlerism’, as the philosopher Hannah Arendt noted in January 1944, exercised its strong international and inter-European appeal during the 1930s ‘because racism, although a state doctrine only in Germany, had been everywhere a powerful trend in public opinion’.2

The organizational backbone of the post-First World War international order was the League of Nations and the bureaucratic backbone of the League of Nations was its permanent Secretariat. The Secretariat was a radically novel invention in international politics. For the first time a permanent, autonomous international body had been created that managed international affairs and was populated with a multinational staff loyal only to that body. This chapter explores how the Secretariat managed to establish and develop this role for itself. It does so through two analytical steps. First, it explores the early, principled decisions regarding the Secretariat’s organization taken by its first Secretary-General, British diplomat Sir Eric Drummond, to ensure the Secretariat became a genuinely international body with substantial institutional autonomy. Second, it maps what we may, with a conceptual loan from Caterina Carta, term the metadiplomatic activities of the Secretariat, i.e. the activities carried out by the Secretariat leadership in order to develop close and productive relations to its main stakeholders: member states, other League institutions and international public opinion with the overall aim of establishing and expanding its legitimacy