The self-interest of leading members
The League depended on the firm support of Britain and France. During conflicts, they were not prepared to abandon their own self-interest to support the League. Economic sanctions did not workLeague members would not impose them since they were worried that without America they would not work. When sanctions were imposed they were easily broken.
Lack of troops
The League had no armed forces and Britain and France were not willing to commit troops.
Decisions were slow
The League met infrequently and took too long to make decisions. The need for all members to agree on a course of action undermined the strength of the League.
America and other important countries were absent
Germany did not join until 1926 and left in 1933. The USSR did not join until 1934 whilst Japan left in 1933 and Italy in 1937. The USA was never a member. The League therefore lacked authority. The Treaties it had to uphold were seen as unfairThe League was supposed to uphold the peace treaties, but it became apparent that there were unfair.
This undermined the league. When the league judged that Japan were wrong, instead of obeying and withdrawing from Manchuria, Japan said they intended to invade more of China and resign from the league proving they were self interested to obey the league. Sanctions would be meaningless without America. The league considered banning arms sales, but member countries disagreed. China and USA put up tariffs against Japanese kids, this put Japan in an economic crisis. Japan had a very powerful army.
There was no prospect of Britain or France risking their navies or armies in a war with Japan. Only the USA or USSR would have the resources to remove the Japanese from Manchuria by force but they were not members of the league. When China appealed to the League, it took a full year for officials of the League to report back from China and Japan what the truth was. (Lytton Report)Japan invaded Manchuria but still wanted more. Britain was too scared to argue in case there was another war. If America would have been present, they could’ve stopped Japan. Germany wanted all the countries to disarm to their level but the conference didn’t agree, so Germany left the conference then the League. If America had been part of the League and disarmed it is most likely that other countries would have followed as America was such an important country and this would have been the same if any other important country had disarmed. Mussolini was humiliated from Abyssinia defeating him and wanted revenge. Britain and France signed the Hoare-Laval Pact agreeing to give Mussolini the best parts of Italy.
When this news reached the media there was an outcry. Sanctions would only work if imposed quickly but each week a decision was delayed. Sanctions were ineffective because they did not include war materials such as oil. As Britain and France had a limited amount of troops, they could not/didn’t want to help Abyssinia and let Mussolini invade the state. The League took too long deciding what to do about Mussolini, so he had time to bring his troops into Abyssinia and build armed forces. When a decision was finally decided, it was ignored.