Collective security can be understood as a security arrangement, regional or global, in which each state in the system accepts that the security of one is the concern of all, and agrees to join in a collective response to threats to, and breaches of, the peace. Collective security is more ambitious than systems of alliance security or collective defence in that it seeks to encompass the totality of states within a region or indeed globally, and to address a wide range of possible threats. While collective security is an idea with a long history, its implementation in practice has proved problematic. Several prerequisites have to be met for it to have a chance of working.
Early mentions 
Collective security is one of the most promising approaches for peace and a valuable device for power management on an international scale. Cardinal Richelieu proposed a scheme for collective security in 1629, which was partially reflected in the 1648 Peace of Westphalia. In the eighteenth century many proposals were made for collective security arrangements, especially in Europe.
The concept of a peaceful community of nations was outlined in 1795 in Immanuel Kant’s Perpetual Peace: A Philosophical Sketch. Kant outlined the idea of a league of nations that would control conflict and promote peace between states. However, he argues for the establishment of a peaceful world community not in a sense that there be a global government but in the hope that each state would declare itself as a free state that respects its citizens and welcomes foreign visitors as fellow rational beings. His key argument is that a union of free states would promote peaceful society worldwide: therefore, in his view, there can be a perpetual peace shaped by the international community rather than by a world government.
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 tranquility 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.
International co-operation to promote collective security originated in the Concert of Europe that developed after the Napoleonic Wars in the nineteenth 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 about humanitarian relief during war and the international Hague Conventions of 1899 and 1907 governing rules of war and the peaceful settlement of international disputes.
The forerunner of the League of Nations, the Inter-Parliamentary Union (IPU), was formed by peace activists William Randal Cremer and Frédéric Passy in 1889. The organization was international in scope with a third of the members of parliament, in the 24 countries with parliaments, serving as members of the IPU by 1914. Its aims were to encourage governments to solve international disputes by peaceful means and arbitration and annual conferences were held to help governments refine the process of international arbitration. The IPU's 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 twentieth century two power blocs emerged through alliances between the European Great Powers. It was these alliances that came into effect at the start of the First World War in 1914, drawing all the major European powers into the war. This was the first major war in Europe between industrialized countries and the first time in Western Europe the results of industrialization (for example mass production) had been dedicated to war. The result of this industrial warfare was an unprecedented casualty level with eight and a half million members of armed services dead, 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 on the continent. 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, secret diplomacy, and the freedom of sovereign states to enter into war for their own benefit. The perceived remedies to these were seen as the creation of an international organization whose aim was to prevent future war through disarmament, open diplomacy, international co-operation, restrictions on the right to wage wars, and penalties that made war unattractive to nations.
Collective security in the League of Nations 
After World War I, the first large scale attempt to provide collective security in modern times was the establishment of the League of Nations in 1919-20. The provisions of the League of Nations Covenant represented a weak system for decision-making and for collective action. An example of the failure of the League of Nations' collective security is the Manchurian Crisis, when Japan occupied part of China (which was a League member). After the invasion, members of the League passed a resolution calling for Japan to withdraw or face severe penalties. Given that every nation on the League of Nations council had veto power, Japan promptly vetoed the resolution, severely limiting the LN's ability to respond. After two years of deliberation, the League passed a resolution condemning the invasion without committing the League's members to any action against it. The Japanese replied by quitting the League.
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 yet in what would become the Axis alliance of World War II. 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.
One active and articulate exponent of collective security during the immediate pre-war years was the Soviet foreign minister Maxim Litvinov. However, there are grounds for doubt about the depth of Soviet commitment to this principle, as well as that of Western powers. After the Munich Agreement in September 1938 and the passivity of outside powers 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.
Recent events 
The 1945 United Nations Charter, although containing stronger provisions for decision-making and collective military action than those of the League of Nations Covenant, does not represent a complete system of collective security, but rather a balance between collective action on the one hand and continued operation of the states system (including the continued special roles of great powers) on the other.
Cited examples of the limitations of collective security include the Falklands War. When Argentina invaded the islands, which are overseas territories of the United Kingdom, many UN members stayed out of the issue, as it did not directly concern them. There was also a controversy about the United States role in that conflict due their obligations as an Inter-American Treaty of Reciprocal Assistance (the "Rio Pact") member. 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.
Collective security can be understood as a security arrangement in which all states cooperate collectively to provide security for all by the actions of all against any states within the groups which might challenge the existing order by using force. This contrasts with self-help strategies of engaging in war for purely immediate national interest. While collective security is possible, several prerequisites have to be met for it to work.
Sovereign nations eager to maintain the status quo, willingly cooperate, accepting a degree of vulnerability and in some cases of minor nations, also accede to the interests of the chief contributing nations organising the collective security. Collective Security is achieved by setting up an international cooperative organisation, under the auspices of international law and this gives rise to a form of international collective governance, albeit limited in scope and effectiveness. The collective security organisation then becomes an arena for diplomacy, balance of power and exercise of soft power. The use of hard power by states, unless legitimised by the Collective Security organisation, is considered illegitimate, reprehensible and needing remediation of some kind. The collective security organisation not only gives cheaper security, but also may be the only practicable means of security for smaller nations against more powerful threatening neighbours without the need of joining the camp of the nations balancing their neighbours.
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." 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.
Basic assumptions 
Organski (1960) lists five basic assumptions underlying the theory of collective security :
- In an armed conflict, member nation-states will be able to agree on which nation is the aggressor.
- All member nation-states are equally committed to contain and constrain the aggression, irrespective of its source or origin.
- All member nation-states have identical freedom of action and ability to join in proceedings against the aggressor.
- The cumulative power of the cooperating members of the alliance for collective security will be adequate and sufficient to overpower the might of the aggressor.
- In the light of the threat posed by the collective might of the nations of a collective security coalition, the aggressor nation will modify its policies, or if unwilling to do so, will be defeated.
Morgenthau (1948) states that three prerequisites must be met for collective security to successfully prevent war :
- The collective security system must be able to assemble military force in strength greatly in excess to that assembled by the aggressor(s) thereby deterring the aggressor(s) from attempting to change the world order defended by the collective security system.
- Those nations, whose combined strength would be used for deterrence as mentioned in the first prerequisite, should have identical beliefs about the security of the world order that the collective is defending.
- Nations must be willing to subordinate their conflicting interests to the common good defined in terms of the common defense of all member-states.
Collective defense 
Collective defense (also collective defense) is an arrangement, usually formalized by a treaty and an organization, among participant states that commit support in defense of a member state if it is attacked by another state outside the organization. NATO is the best known collective defense organization. Its now famous Article V calls on (but does not fully commit) member states to assist another member under attack. This article was invoked after the September 11 attacks on the United States, after which other NATO members provided assistance to the US War on Terror in Afghanistan. Collective defense has been shown to be very helpful to all countries.
Collective defense has its roots in multiparty alliances, and entails benefits as well as risks. On the one hand, by combining and pooling resources, it can reduce any single state's cost of providing fully for its security. Smaller members of NATO, for example, have leeway to invest a greater proportion of their budget on non-military priorities, such as education or health, since they can count on other members to come to their defense, if needed.
On the other hand, collective defense also involves risky commitments. Member states can become embroiled in costly wars in which neither the direct victim nor the aggressor benefit. In the First World War, countries in the collective defense arrangement known as the Triple Entente (France, Britain, Russia) were pulled into war quickly when Russia started full mobilization against Austria-Hungary, whose ally Germany subsequently declared war on Russia.
See also 
- North Atlantic Treaty Organisation
- Inter-American Treaty of Reciprocal Assistance
- European Common Security and Defence Policy
- Shanghai Cooperation Organization
- Collective Security Treaty Organization
- African Union
- Peace and Security Council
- Union of South American Nations
- Organization of the Eurasian Law Enforcement Agencies with Military Status
- First World War
- Second World War
- Soviet-German relations before 1941
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