The lines between what is considered "collective defense" and "collective security" have been blurred. The concept of "collective security" forwarded by men such as Michael Joseph Savage, Martin Wight, Immanuel Kant, and Woodrow Wilson, are deemed to apply interests in security in a broad manner, to "avoid grouping powers into opposing camps, and refusing to draw dividing lines that would leave anyone out. Tenets of collective security continue to be behind many famous current and historical military alliances, most notably NATO. The term "collective security" has also been cited as a principle of the United Nations, and the League of Nations before that. By employing a system of collective security, the UN hopes to dissuade any member state from acting in a manner likely to threaten peace, thereby avoiding any conflict.
A similar process occurred in 1935, when Italy invaded Ethiopia. Sanctions were passed, but Italy would have vetoed any stronger resolution. Additionally, Britain and France sought to court Italy's government as a potential deterrent to Hitler, given that Mussolini was not in what would become the Axis alliance of WWII. Thus, neither enforced any serious sanctions against the Italian government. Additionally, in this case and with the Japanese invasion of Manchuria, the absence of the USA from the League of Nations deprived the LN of another major power that could have used economic leverage against either of the aggressor states. Inaction by the League subjected it to criticisms that it was weak and concerned more with European issues (most leading members were European), and did not deter Hitler from his plans to dominate Europe. The Ethiopian monarch Emperor Haile Selassie I continued to support collective security though, having assessed that impotence lay not in the principle but in its covenantors commitment to honor its tenets.
The most active and articulate exponent of collective security during the immediate pre-war years was the Soviet foreign minister Maxim Litvinov, but after the Munich Agreement in September 1938 and Western passivity in the face of German occupation of the remainder of Czechoslovakia in March 1939 it was shown that the Western Powers were not prepared to engage in collective security against aggression by the Axis Powers together with the Soviet Union, Soviet foreign policy was revised and Litvinov was replaced as foreign minister in early May 1939, in order to facilitate the negotiations that led to the Molotov-Ribbentrop Pact with Germany, signed by Litvinov's successor, Vyacheslav Molotov, on August 23 of that year. The war in Europe broke out a week later, with the German invasion of Poland on September 1.
However, many politicians who view the system as having faults also believe it remains a useful tool for keeping international peace.
The role of the UN and collective security in general is also evolving given the rise of internal state conflicts since the end of WWII, there have been 111 military conflicts world wide, but only 9 of which have involved two or more states going to war with one another. The remainder have either been internal civil wars or civil wars where other nations intervened in some manner. This means that collective security may have to evolve towards providing a means to ensure stability and a fair international resolution to those internal conflicts. Whether this will involve more powerful peacekeeping forces or a larger role for the UN diplomatically will likely be judged from a case to case basis.
The time must come when the imperative necessity for the holding of a vast, an all-embracing assemblage of men will be universally realized. The rulers and kings of the earth must needs attend it, and, participating in its deliberations, must consider such ways and means as will lay the foundations of the world's Great Peace amongst men. Such a peace demandeth that the Great Powers should resolve, for the sake of the tranquillity of the peoples of the earth, to be fully reconciled among themselves. Should any king take up arms against another, all should unitedly arise and prevent him. If this be done, the nations of the world will no longer require any armaments, except for the purpose of preserving the security of their realms and of maintaining internal order within their territories. This will ensure the peace and composure of every people, government and nation.