Between 1920 and 1946, a total of 63 countries became member states of the League of Nations.
When the Assembly of the League of Nations first met, it consisted of 42 founding members. A further 21 countries joined between then and the dissolution of the League.
Since various nations left the League at different points, its full roster of 63 countries was never represented simultaneously. The League's greatest extent was from 28 September 1934 (when Ecuador joined) to February 1935 (when Paraguay withdrew) with 58 countries. At this time, only Costa Rica (December 1924), Brazil (June 1926), Japan (March 1933), and Germany (October 1933) had withdrawn, and only Egypt joined later (on 26 May 1937).
Founding members The Covenant of the League of Nations was part of the Treaty of Versailles, signed on 28 June 1919 between the Allies of World War I and Germany. In order for the treaty to enter into force, it had to be deposited at Paris; in order to be deposited, it had to be ratified by Germany and any three of the five Principal Powers (the United States of America, the British Empire, France, Italy, and the Empire of Japan). Any Allied signatory that ratified the treaty would automatically join the League.
Germany was forced to ratify the treaty first,O'Brien, Terrence, "Milner", London: Constable, 1979. pg. 338. which it did on 10 July 1919. Italy ratified on 7 October 1919, the British Empire and its colonies ratified on 10 October 1919, and France ratified on 12 October 1919. These ratifications were deposited (along with those of ten other countries) on 10 January 1920. All but three of the remaining signatories (the United States, Ecuador, and the Kingdom of Hejaz) had ratified by the time the Assembly first met on 15 November 1920.
The Covenant also invited 13 neutral nations to join the League. To join, an invitee had to agree ("accede without reservation") to the Covenant within two months of the League's founding. All 13 invitees accepted their invitations within the two-month deadline; four of them accepted their invitations even before the League was founded.
The United States Senate voted in favor of ratification, but this failed to reach the necessary two-thirds majority. Hejaz refused to join the League due to the League giving control of Palestine from the broken-up Ottoman Empire to the British Empire. Ecuador would not ratify the treaty until 1934; as an original Allied signatory, it was entitled to join the League this way with no deadline or Assembly vote, and the League considered Ecuador to still be a founding member.
Uniquely, China (then the Beiyang government) joined the League by ratifying the Treaty of St. Germain (with Austria) instead of the Treaty of Versailles (with Germany), as both treaties included the Covenant of the League of Nations. It had refused to sign the Treaty of Versailles due to it giving the previously-German-controlled Shandong colony in China to the Empire of Japan.
Additional members could join the League by a two-thirds vote of the Assembly.
List Founding members below are listed in the order matching the Covenant (signatories first, followed by invitees), except for Ecuador. The colonies of the British Empire immediately followed it and did not sign in alphabetical order. Czechoslovakia and El Salvador were alphabetized under 'S'.
A country was allowed to send a withdrawal notice at any time, but it would take two years to come into effect after the League received it, and meanwhile the country would retain both its obligations and its membership. In practice, a withdrawing country quit the League immediately, and was absent from all sessions and votes for the last two years of its formal membership. The "Date of withdrawal" column shows when the withdrawal notice was sent.
+ List of members Member state Date of admission Date of withdrawal Notes Withdrew upon rejection of a resolution to give Brazil the United States' vacant permanent Council seat. All six members joined from one ratification document. Vichy France sent a notice of withdrawal , which the League recognized. Free France did not recognize Vichy France's withdrawal and rescinded the notice 15 and 16 April 1943, which the League also recognized. Withdrawal notice received by the League 26 May 1936. Withdrawal notice received by the League 8 April 1942. Withdrawal notice received by the League 10 July 1936. Quit after the League sanctioned it for invading Ethiopia. Quit after the League refused to recognize the puppet state of Manchukuo. Hannsjoachim Wolfgang Koch, Macmillan International Higher Education, 1985, Aspects Of The Third Reich, p. 297 Kingdom of Serbs,Croats, and Slovenes Renamed Yugoslavia in 1929. Siam Renamed Thailand in 1939. Czechoslovakia Occupied and annexed by Nazi Germany ; never withdrew. Invitee; accepted .Quit without sending a notice of withdrawal;South America , Encyclopedia of World History resumed participation .League of Nations chronology, United Nations Invitee; accepted . Invitee. Invitee.Occupied by Nazi Germany and forced to withdraw ; withdrawal not recognized by the League. Withdrawal notice rescinded in 1945. Invitee. Invitee. Invitee; accepted .Quit during the Chaco War after rejecting the League's arbitration. Invitee; accepted .Renamed Iran in 1935. Invitee.Withdrawal notice received by the League 10 August 1938. Spain Spanish Republic Invitee.Withdrew with the formal 2-year notice; rejoined before the 2 years were up.Quit after Francisco Franco came to power. Invitee. Invitee. Invitee. Austria The League recognized the Anschluss (five days afterward) and removed Austria from its list of members.List of States Members of the League of Nations on 31.XII.1944 from the League of Nations Statistical Yearbook (1942-44) Costa Rica Gave slightly more than two years' notice, with its membership formally ceasing . Occupied by Italy 12 April 1939; the puppet government sent a notice of withdrawal to the League , but the League did not recognize the puppet government or accept the notice. Occupied by the Soviet Union and annexed ; never withdrew. Occupied by the Soviet Union and annexed ; never withdrew. Occupied by the Soviet Union and annexed ; never withdrew. Renamed Ireland in 1937. Abyssinia The League switched from using "Abyssinia" to "Ethiopia" between September 1934 and September 1935.Occupied by the Italian Empire and annexed from to ; never withdrew. Dominican Republic Quit after Hitler came to power. The League invited Mexico to join on 8 September 1931.Toledo-García, Itzel; University of Essex, UK: ‘’"La cuestión de la dignidad nacional en el ingreso de México a la Sociedad de Naciones, 1919-1931"’’ Retrieved 4 September 2016. (Translated from Spanish: "On September 7th, 1931, the British Empire, Germany, Northern Ireland, Spain, France, Italy and Japan began the initiative; next day the proposal was adopted unanimously by the assembly, and the invitation was sent to the government of Mexico. The 10th of September the acceptance was communicated in Geneva… Two days later, Mexico was declared member of the League of Nations.")
Expulsion of the Soviet Union On 14 December 1939, the Soviet Union was expelled for invading Finland in violation of the Covenant of the League of Nations, by a Council vote of 7–0–4–3 (7 in favor, 0 against, 4 abstaining, 3 absent). The United Kingdom, France, Belgium, Bolivia, the Dominican Republic, South Africa, and Egypt voted in favor; the Republic of China, Finland, Greece, and Yugoslavia abstained; and Iran, Peru, and the Soviet Union itself were absent. Three of the votes in favor had been made Council members the day before the vote (South Africa, Bolivia, and Egypt). This was one of the League's final acts before it practically ceased to function.
It has been disputed whether the expulsion was legally valid. Article 16 paragraph 4 of the Covenant stated that the Council may expel a member from the League if all members of the Council other than the to-be-expelled member concur. However, it is unclear if abstentions or absences were permitted for expulsion votes, though it is undisputed that they were allowed for all of the Council's other unanimous decisions. Even so, it is disputed whether the expulsion could be legally valid without a majority (8 out of 14) of the Council in favor.
Regardless, both the expulsion and any possible dispute of it had little practical effect. The Soviet Union had already declared nine days earlier that it would be absent from the League until further notice; it acknowledged its expulsion and made no effort to challenge it on any grounds. No other member was ever expelled from the League to demonstrate any precedent, and the League took no further significant actions with the outbreak of the Second World War.
Non-members Between November and December 1920, Armenia, Azerbaijan, Georgia, and Ukraine applied for membership amid the dissolution of the Russian Empire and the Russian Civil War, but were denied because they did "not appear to have a stable government whose authority extends over the whole of its territory". (Some extra consideration was given to Armenia due to it being a signatory of the Treaty of Sèvres, which would have given Armenia some territory from the broken-up Ottoman Empire, but the treaty failed to be ratified.) Estonia, Latvia, and Lithuania also applied in 1920 and were denied that year because they "had not achieved a definite international status" at the time (the three would be admitted the next year).
Some of the European microstates, namely Liechtenstein, Monaco, and San Marino, also applied for membership but were denied, explicitly "by reason of their small size". Monaco applied for membership on April 6, 1920, but withdrew the application on October 22, 1920. San Marino applied on April 25, 1919, but its application lapsed when it failed to respond to a request for information by August 22, 1920. Liechtenstein pursued its application with vigor, leading its application to be considered by the League admissions committee. The committee concluded, "there can be no doubt that juridically the Principality of Liechtenstein is a sovereign State", but found that because Liechtenstein delegated some state functions to other states, it "could not discharge all the international obligations which would be imposed on her by the Covenant." The committee voted 28 to 1 (with only Switzerland voting in favor of admission) against admission for Liechtenstein (with 13 abstentions). The decision has been criticized by international lawyers who have noted that other entities, which lacked the powers typically associated with sovereign states, were allowed to be member states.
Andorra and Vatican City never sought membership. Iceland was given the opportunity to join the League of Nations in 1920, but opted not to, primarily due to limited administrative resources.
Newfoundland was the only British dominion which did not apply for membership of the League, which Arthur Berriedale Keith attributed to its "small size and microscopic population" (less than 300,000 people at the time). It had also been denied separate representation at the Paris Peace Conference and was less active in foreign affairs compared to the other dominions.
Some relatively-isolated sovereign states in Asia also did not join, including Bhutan, Nepal, and Yemen, at least in part due to having no diplomatic relations with the major powers. Mongolia (from 1921) and Tibet were de facto independent, but their independence was not recognized by the major powers.
The Kingdom of Hejaz declined to join in 1920, and was conquered by the Sultanate of Nejd in 1925, creating the Kingdom of Hejaz and Nejd. The dual monarchy was consolidated to become Saudi Arabia in 1932. Saudi Arabia never joined the League.
The Sultanate of Muscat and Oman never joined the League of Nations; it was de jure an independent state but was considered a de facto British protectorate.