The concept of a peaceful community of nations had been proposed as far back as 1795, when
Perpetual Peace: A Philosophical Sketch
 outlined the idea of a league of nations to control conflict and promote peace between states. Kant argued for the establishment of a peaceful world community, not in a sense of a global government, but in the hope that each state would declare itself a free state that respects its citizens and welcomes foreign visitors as fellow rational beings, thus promoting peaceful society worldwide.
 International co-operation to promote collective security originated in the
Concert of Europe that developed after the
Napoleonic Wars in the 19th century in an attempt to maintain the status quo between European states and so avoid war. This period also saw the development of international law, with the first
Geneva Conventions establishing laws dealing with humanitarian relief during wartime, and the international
Hague Conventions of 1899 and 1907 governing rules of war and the peaceful settlement of international disputes. As historian
Ronald E. Powaski points out,
Theodore Roosevelt was the first American President to call for an international league.
 At the acceptance for his Nobel Prize, Roosevelt said: "it would be a masterstroke if those great powers honestly bent on peace would form a League of Peace"
The forerunner of the League of Nations, the
Inter-Parliamentary Union, was formed by the peace activists
William Randal Cremer and
Frédéric Passy in 1889. The organisation was international in scope, with a third of the members of
parliaments (in the 24 countries that had parliaments) serving as members of the IPU by 1914. Its aims were to encourage governments to solve international disputes by peaceful means. Annual conferences were held to help governments refine the process of international arbitration. Its
structure consisted of a council headed by a president, which would later be reflected in the structure of the League.
At the start of the 20th century, two power blocs emerged from alliances between the European
Great Powers. It was these alliances that, at the
start of the First World War in 1914, drew all the major European powers into the conflict. This was the first major war in Europe between industrialised countries, and the first time in Western Europe that the results of
industrialisation (for example, mass production) had been dedicated to war. The result of this industrialised warfare, which provided modern weapons, coupled with outdated 19th century strategies, led to an unprecedented casualty level: eight and a half million soldiers killed, an estimated 21 million wounded, and approximately 10 million civilian deaths.
By the time the fighting ended in November 1918, the war had had a profound impact, affecting the social, political and economic systems of Europe and inflicting psychological and physical damage. Anti-war sentiment rose across the world; the First World War was described as "
the war to end all wars", and its possible causes were vigorously investigated. The causes identified included arms races, alliances, militaristic nationalism, secret diplomacy, and the freedom of sovereign states to enter into war for their own benefit. One proposed remedy was the creation of an international organisation whose aim was to prevent future war through disarmament, open diplomacy, international co-operation, restrictions on the right to wage war, and penalties that made war unattractive.
, one of the earliest advocates for a League of Nations.
At the start of the First World War the first schemes for international organisation to prevent future wars began to gain considerable public support, particularly in the
United Kingdom and the
Goldsworthy Lowes Dickinson, a British political scientist, coined the term "League of Nations" in 1914 and drafted a scheme for its organisation. Together with
Lord Bryce, he played a leading role in the founding of the group of internationalist pacifists known as the Bryce Group, later the
League of Nations Union.
 The group became steadily more influential among the public and as a pressure group within the then governing
Liberal Party. In Dickinson's 1915 pamphlet After the War he wrote of his "League of Peace" as being essentially an organisation for arbitration and conciliation. He felt that the secret diplomacy of the early twentieth century had brought about war and thus could write that, "the impossibility of war, I believe, would be increased in proportion as the issues of foreign policy should be known to and controlled by public opinion." The ‘Proposals’ of the Bryce Group were circulated widely, both in England and the US, where they had a profound influence on the nascent international movement.
In 1915, a similar body was set up in the United States by a group of like-minded individuals, including
William Howard Taft. It was called the
League to Enforce Peace and was substantially based on the proposals of the Bryce Group.
 It advocated the use of arbitration in conflict resolution and the imposition of sanctions on aggressive countries. However, none of these early organisations envisioned a continuously functioning body; with the exception of the
Fabian Society in
England, they maintained a legalistic approach that would limit the international body to a court of justice. The Fabians were the first to argue for a "Council" of states, necessarily the
Great Powers, who would adjudicate world affairs, and for the creation of a permanent secretariat to enhance international co-operation across a range of activities.
Lord Balfour commissioned the first official report into the matter in early 1918, under the initiative of Lord
Robert Cecil. The British committee was finally appointed in February 1918. It was led by
Walter Phillimore (and became known as the Phillimore Committee), but also included
William Tyrrell, and
 The recommendations of the so-called
Phillimore Commission included the establishment of a "Conference of Allied States" that would arbitrate disputes and impose sanctions on offending states. The proposals were approved by the British government, and much of the commission's results were later incorporated into the
Covenant of the League of Nations.
The French also drafted a much more far-reaching proposal in June of that year; they advocated annual meetings of a council to settle all disputes, as well as an "international army" to enforce its decisions.
The American President
Woodrow Wilson instructed
Edward M. House to draft a US plan which reflected Wilson's own idealistic views (first articulated in the
Fourteen Points of January 1918), as well as the work of the Phillimore Commission. The outcome of House's work, and Wilson's own first draft, proposed the termination of "unethical" state behaviour, including forms of espionage and dishonesty. Methods of compulsion against recalcitrant states would include severe measures, such as "blockading and closing the frontiers of that power to commerce or intercourse with any part of the world and to use any force that may be necessary..."
The two principal drafters and architects of the
covenant of the League of Nations
 were Lord
Robert Cecil (a
Jan Smuts (a
Commonwealth statesman). Smuts' proposals included the creation of a Council of the
great powers as permanent members and a non-permanent selection of the minor states. He also proposed the creation of a
Mandate system for captured colonies of the
Central Powers during the war. Cecil focused on the administrative side, and proposed annual Council meetings and quadrennial meetings for the Assembly of all members. He also argued for a large and permanent secretariat to carry out the League's administrative duties.
The official opening of the League of Nations, 15 November 1920
Paris Peace Conference in 1919, Wilson, Cecil, and Smuts all put forward their draft proposals. After lengthy negotiations between the delegates, the
Miller draft was finally produced as a basis for the
 After more negotiation and compromise, the delegates finally approved of the proposal to create the League of Nations (
French: Société des Nations,
German: Völkerbund) on 25 January 1919. The final
Covenant of the League of Nations was drafted by a special commission, and the League was established by Part I of the
Treaty of Versailles. On 28 June 1919, 44 states signed the Covenant, including 31 states which had taken part in the war on the side of the
Triple Entente or joined it during the conflict.
The League would be made up of a General Assembly (representing all member states), an Executive Council (with membership limited to major powers), and a permanent secretariat. Member states were expected to "respect and preserve as against external aggression" the territorial integrity of other members and to
disarm "to the lowest point consistent with domestic safety." All states were required to submit complaints for
judicial inquiry before going to war.
 The Executive Council would create a
Permanent Court of International Justice to make judgements on the disputes.
Despite Wilson's efforts to establish and promote the League, for which he was awarded the
Nobel Peace Prize in October 1919, the United States did not join. Opposition in the Senate, particularly from two Republican politicians,
Henry Cabot Lodge and
William Borah, and especially in regard to
Article X of the Covenant, ensured that the United States would not ratify the agreement.
The League held its first council meeting in Paris on 16 January 1920, six days after the Versailles Treaty and the Covenant of the League of Nations came into force. On 1 November 1920, the headquarters of the League was moved from London to Geneva, where the first General Assembly was held on 15 November 1920.