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Collective security

Another important weakness grew from the contradiction between the idea of collective security that formed the basis of the League and international relations between individual states. The League's collective security system required nations to act, if necessary, against states they considered friendly, and in a way that might endanger their national interests, to support states for which they had no normal affinity. This weakness was exposed during the Abyssinia Crisis, when Britain and France had to balance maintaining the security they had attempted to create for themselves in Europe "to defend against the enemies of internal order", in which Italy's support played a pivotal role, with their obligations to Abyssinia as a member of the League.

On 23 June 1936, in the wake of the collapse of League efforts to restrain Italy's war against Abyssinia, the British Prime Minister, Stanley Baldwin, told the House of Commons that collective security had

failed ultimately because of the reluctance of nearly all the nations in Europe to proceed to what I might call military sanctions... The real reason, or the main reason, was that we discovered in the process of weeks that there was no country except the aggressor country which was ready for war... f collective action is to be a reality and not merely a thing to be talked about, it means not only that every country is to be ready for war; but must be ready to go to war at once. That is a terrible thing, but it is an essential part of collective security.

Ultimately, Britain and France both abandoned the concept of collective security in favour of appeasement in the face of growing German militarism under Hitler. In this context, the League of Nations was also the institution where the first international debate on terrorism took place following the 1934 assassination of King Alexander I of Yugoslavia in Marseille, France. This debate established precedents regarding global surveillance (in the form of routine international sharing of surveillance data), the punishment of terrorists as an international (rather than national) matter, and the right of a nation to conduct military attacks within another nation as a response to international terrorism. Many of these concepts are detectable in the discourse of terrorism among states after 9/11.

American diplomatic historian Samuel Flagg Bemis originally supported the League, but after two decades changed his mind:

The League of Nations has been a disappointing failure.... It has been a failure, not because the United States did not join it; but because the great powers have been unwilling to apply sanctions except where it suited their individual national interests to do so, and because Democracy, on which the original concepts of the League rested for support, has collapsed over half the world.