The Hague period of modern internationalism ended abruptly with the declarations of war. The Pacific Settlement Convention and the treaties of arbitration and conciliation were brushed aside as the armies of the warring nations hastened to secure strategic positions. Four years later, as the war moved toward its close, European nations and the United States advocated a world organization. Occasionally there were recommendations that the new world system be founded on the work of the Hague conferences, but at Paris, in 1919, Wilson and other internationalists sought to break with the Hague traditions as they planned the League of Nations.
Fundamental in Wilson's thinking was the famous pledge in Article X of the League of Nations Covenant "to respect and preserve as against external aggression the territorial integrity and existing political independence" of the league's members. Wilson's small respect for the work of the Hague conferences notwithstanding, other members of the drafting committee incorporated into the covenant the prewar experience with arbitration and conciliation. Members of the league were to refer disputes that threatened rupture to arbitration, judicial settlement, or inquiry by the League Council. Parties to a dispute were not to go to war for three months after arbitral awards, judicial decisions, or reports from the council. The league convened a conference of experts at The Hague in 1920 to draft a statute for a new international court. The conference took the 1907 draft Hague convention for a Court of Arbitral Justice as the basis of its work and quickly produced the draft Statute for the Permanent International Court of Justice. The older Permanent Court of Arbitration was to have a special role in the new judicial system: its judges were to meet in national groups to make nominations for the new court. The Permanent Court of International Justice met for the first time in the Peace Palace at The Hague in 1922. The creation of the Permanent Court, usually called the World Court, was a special challenge to the United States. Elihu Root and James Brown Scott were among the experts who drafted the World Court Statute. Despite the failure of the United States to ratify the Treaty of Versailles and the attached Covenant of the League of Nations, adherence to the statute was possible. The isolationism resulting from the league struggle was, however, so strong that even the court aroused senatorial opposition. Presidents and secretaries of state during the 1920s and 1930s made several attempts to secure American entry into the World Court system. All failed. Secretaries of state, nevertheless, pursued arbitration policies like those of Elihu Root, renewing Root's treaties and negotiating entirely new arbitration agreements. The United States was one of sixteen republics at a Pan-American conference in Santiago, Chile, in 1923 that signed a treaty providing for commissions of inquiry to investigate disputes neither diplomacy nor arbitration could settle. At the Conference on Conciliation and Arbitration in Washington on 5 January 1929, the United States was one of twenty American republics signing a general arbitration treaty and conciliation convention.
The European experience with peaceful settlement between the world wars was no more promising than that of the United States. The World Court decided several cases, and governments continued to make use of arbitration. The Geneva Protocol was an important proposal to strengthen the covenant's arbitration provisions, but it failed in 1925 when a new Conservative government in London withdrew support. Later that year, at the Locarno conference, the German government concluded treaties with Belgium and France recognizing their boundaries with Germany and concluded arbitration treaties with those two countries and Poland and Czechoslovakia. All such initiatives for peace were swept aside when World War II began.