Guaranteeing Peace through “Collective Security” in the 20th Century

“Collective security”, an expression that emerged in the 1930s, is an attempt to respond to the outbreak of violence in the two world wars of the twentieth century. In contrast to the notion of security through a balance of power, which characterised the international system in the nineteenth century, collective security instead relies on the “imbalance of power” (Marie-Claude Smouts and Guillaume Devin) that would be amassed by all member states against any aggressor. This system was first institutionalised in the aftermath of the First World War by the League of Nations and taken up again in 1945 by the United Nations. While never bringing the results hoped for by its advocates, it nevertheless marks a turning point in the history of international relations.

‘The doormat’, satirical drawing by David Low (1891-1963), published in the Evening Standard, 19 January 1933.

The pioneering role of the League of Nations

Hoping to break with the system of alliances and secret diplomacy which was held responsible for the cataclysm of 1914-1918, the American president Woodrow Wilson placed the creation of the League of Nations at the top of the agenda during the 1919 Peace Conference, in order to base the preservation of peace on new practices. Thus, the Covenant of the League of Nations, adopted on 28 April 1919, provided that “the members of the League undertake to respect and preserve against external aggression the territorial integrity and existing political independence of all members of the League” (Art. 10) and that, should any member “resort to war […], it shall ipso facto be deemed to have committed an act of war against all other members of the League” (Art. 16).

However, the means at the disposal of the League to enforce this commitment were rather limited. The Covenant stipulated that any dispute should be submitted to arbitration or to consideration by the Council of the League, but if the Council could not unanimously identify the aggressor, each member state recovered its freedom of action. In the case of unanimity, Article 16 obliged the League’s member states to take part in economic and financial sanctions against the state recognised as the aggressor, but their participation in military action, which required the unanimous agreement of the Council, remained optional. Far removed from the French plans for a strong League of Nations with a permanent international military staff, the Covenant of the League thus mainly reflected Anglo-American plans, which emphasised the public nature of the proceedings and the moral pressure of public opinion to prevent conflict.

From 1920, the League also found itself weakened by the refusal of the United States to join, and its destiny henceforth bore the mark of the Franco-British “mésentente cordiale.” Its ability to settle international disputes was thus limited to conflicts that did not call into question the interests of the Great Powers.

Anxious to clarify the mechanisms of collective security, the General Assembly of the League nevertheless adopted, on 2 October 1924, a “Protocol for the Peaceful Settlement of International Disputes” which contained significant advances: to refuse arbitration would be equated with aggression, and military assistance would become obligatory once it had been voted by two thirds of the Council. However, this Protocol ultimately failed owing to the refusal of the British Conservatives, now back in power, to ratify it.

The failure of the 1930s

The collective security system experienced resounding failures in the 1930s, showing itself incapable of guaranteeing the protections of Article 10 to those members threatened by the aggressive policies of dictatorial regimes. It proved unable in 1931-1932, for instance, to prevent the conquest of Manchuria by Japan, a permanent member of the Council of the League which withdrew in 1933 when condemned by the Geneva-based institution. In 1935 the League was brought into disrepute through the aggression of Italy against Ethiopia, a member of the League since 1923: under the pressure of the small and medium powers, France and Britain resigned themselves to implementing Article 16 of the Covenant, but the economic sanctions voted against Italy proved ineffective due to the neutrality of the United States and the fact that oil and other strategic products were not subject to the embargo. Treated with leniency by France and the United Kingdom, which were counting on its support to contain the revisionist policies of Hitler’s Germany, Italy ultimately decided to annex Ethiopia in May 1936.

The false hopes of the UN

The principle of collective security was nevertheless adopted once more by the United Nations, established by the San Francisco Charter on 26 June 1945. Aware of the weaknesses of the League of Nations, however, its founders attempted to improve the mechanisms of collective security by giving a decisive role to the principal victors of the Second World War, which became permanent members of the Security Council (USA, USSR, China, UK, France) and were assigned the role of “policemen” within the new international system. The Security Council, on which the Big Five have the power of veto, was given “the primary responsibility for the maintenance of international peace and security” (Art. 24). In the case of a threat to peace or act of aggression, the Security Council can decide on economic sanctions (Art. 41) or to “take such action by air, sea or land forces as may be necessary to maintain or restore international peace and security” (Art. 42). It was intended that all member states would commit to making a certain number of armed forces available to the Security Council, under special agreements that would specify their size, composition, degree of readiness and location, but these agreements were never actually established. The use of these forces was meant to be planned by an international military staff, but this was never put into practice. The disagreements between the great powers, linked to the emergence of the Cold War, quickly brought about the paralysis of the UN, a fact that played a significant role in the Korean War (1950-1953), the American intervention (bringing together 17 countries) only being legitimized by the Security Council in the temporary absence of the Soviets.

In the absence of a veritable system of collective security, international security was therefore based primarily on collective defence organisations (principally NATO and the Warsaw Pact). The UN Charter did not, in fact, call into question the “inherent right of individual or collective self-defence” (Art. 51) or “the existence or regional arrangements or agencies for dealing with such matters relating to the maintenance of international peace and security” (Art. 52).

The end of the Cold War provided hope, in the context of a “new world order,” of a revitalisation of the UN and the rebirth of collective security, as witnessed during the First Gulf War (1990-1991) where the use of force against Iraq was legitimized by a resolution adopted by the Security Council. However, these hopes were soon dashed, and the UN does not seem capable, at the beginning of the 21st century, of providing real answers to problems of international security. Its actions in favour of peace are conducted primarily within the framework of peacekeeping operations.

To quote from this article

Jean-Michel Guieu , « Guaranteeing Peace through “Collective Security” in the 20th Century », Encyclopédie d'histoire numérique de l'Europe [online], ISSN 2677-6588, published on 22/06/20 , consulted on 12/07/2024. Permalink :


Bertrand, Maurice, L’ONU, Paris, La Découverte, coll. "Repères", 2009.

Gerbet, Pierre, Ghebali, Victor-Yves, Mouton, Marie-Renée, Le rêve d’un ordre mondial de la SDN à l’ONU, Paris, Imprimerie nationale, 1996.

Orakhelashvili, Alexander, Collective Security, Oxford, Oxford University Press, 2011.


Don’t miss a single publication! Register now to receive our newsletter in English:

The subscriber's email address.
Manage your newsletter subscriptions
Select the newsletter(s) to which you want to subscribe.