After the horrors of World War I, the world needed a system to prevent another global conflict. French statesman Léon Bourgeois strongly advocated a permanent organization where nations could discuss as equals and settle disputes by words, not weapons. The Covenant of the League of Nations adopted at the 1919 Paris Peace Conference reflected his philosophy of international solidarity. In 1920 Bourgeois, as President of the League’s first Assembly, guided membership approvals and parliamentary procedures, officially launching a framework of collective security. Although the League lacked strong military enforcement, the idea that many countries cooperate to keep peace was carried forward into today’s United Nations. Bourgeois’s work also energized citizen peace movements and the evolution of international law, which the Nobel Committee recognized by awarding him the Peace Prize.

The League of Nations was established as part of the 1919 Treaty of Versailles and began operating in Geneva in 1920. Léon Bourgeois, a former French Prime Minister, had emphasized judicial methods since proposing compulsory arbitration at the 1899 Hague Peace Conference. His doctrine of “international solidarism” extended domestic social solidarity to the international arena, aiming to create a moral law that would temper absolute sovereignty. The League’s Covenant institutionalized a “cooling‐off period,” requiring states to submit disputes to an international court or the Council and refrain from force while the case was heard. Under Bourgeois’s presidency, the 1920 Assembly adopted mandates for former colonies and resolutions to found the Permanent Court of International Justice (PCIJ), shaping not only collective security but also colonial administration and international adjudication. He mediated Anglo-French disagreements and balanced unanimity rules with practical decision-making, ensuring smooth proceedings. Despite structural weaknesses such as U.S. absence and great-power rivalries, the League pioneered minority protection treaties and agencies like the ILO, foreshadowing modern multilateral institutions. Bourgeois’s ideas and practice are still studied as prototypes of institutional innovation in international organization and norm formation. His Nobel Peace Prize thus marked early global recognition of these groundbreaking efforts.

As a Radical thinker of France’s Third Republic, Bourgeois applied Durkheimian social solidarity to international politics, formulating a sovereignty-limiting model of ‘solidarist peace’. His draft clauses on compulsory arbitration at the 1899 and 1907 Hague Conferences later materialized in Article 14 of the League Covenant and the statute of the PCIJ. Serving as President of the 1920 Assembly, he mediated Anglo-French disputes over Covenant interpretation and engineered a procedural ‘alternative voting mechanism’ that partially relaxed the unanimity rule. He also offered an expansive reading of Article 16 on economic sanctions, advocating an automatic trigger principle that became a legal basis during the 1935 Italo-Ethiopian crisis. Bourgeois’s peace theory influenced monist international jurists such as Kelsen and fed into governance concepts centered on the rule of law. His inclusion of social rights and public order within inter-state solidarity, however, differentiated him from Anglo-American liberal internationalism and sparked theoretical debates. The 1920 Nobel award publicly certified his influence within the Geneva diplomatic community, illustrating the prize’s political signaling function. Primary sources include his speech drafts (Archives Nationales, 446AP) and League Assembly records (A/6/PV.1-25). From an institutional-design perspective, his blend of automatic sanctions with mandatory arbitration represents an early model integrating compliance cost calculus with escalation control.