After 11 November 1918, the cry of 'No war ever again’ sounded out louder than ever before. The countries that negotiated the peace accord were in agreement that the text of the treaty should contain sufficient guarantees to prevent future wars. One of these guarantees was the foundation of a League of Nations that would devote itself to the preservation of mutual peace. The American president, Woodrow Wilson, was the leading advocate of this. 
 
The countries that belonged to the victors' camp accepted the principle of a general assembly of nations in January 1919. The League of Nations was born; the organisation was able to begin actively a year later. At that moment, the League of Nations had 45 members. Later, the defeated countries in the war were also invited to join, and the number of member nations rose to 58. The ambitions of the new international organisation were not insignificant. The member nations committed themselves to submit future differences to the international court of the League of Nations, the Permanent Court of International Justice. In that way, differences between states would be settled on the basis of international law from then on, rather than the clash of arms. However, the high expectations were immediately crippled: the American Congress refused to ratify the Covenant of the League of Nations and thereby effectively blocked the entry of the United States into the new organisation, even though it was the brainchild of their own president. 
 
Although the League of Nations did initially achieve some successes, it ultimately proved too weak to fulfil its ambitions. In the 1930s, Japan, Italy and Germany left the League of Nations. The organisation was not capable of undertaking any action against the increasing aggression of Nazi Germany and other dictatorial regimes. The League of Nations quickly lost its significance, but did form the blueprint for the United Nations, the international organisation that was founded after The Second World War.