Warfare and the United Nations Summary

  • Last updated on November 11, 2022

International law recognizes the right of states to defend themselves.

Political Considerations

International law recognizes the right of states to defend themselves. The United Nations system requires all states to abide by Article 2.4 of the U.N. Charter, prohibiting threat and use of force while also requiring that states resort only to peaceful countermeasures when addressing a breach of their legal rights by another state.United NationsInternational lawUnited Nations peacekeeping operationsPeacekeeping operations, U.N.United NationsInternational lawUnited Nations CharterUnited Nations peacekeeping operationsPeacekeeping operations, U.N.

Chapter VII of the U.N. Charter vests the United Nations Security CouncilU.N. Security Council with broad powers of forcible intervention. It can intervene whenever it determines, under Article 39, that there exists a threat to the peace, a breach of the peace, or an act of aggression. It can then decide, under Article 41, upon Sanctions, U.N.sanctions that do not involve the use of force of arms, or it can then decide, under Article 42, to take action by force of arms against the aggressor or the state threatening peace.

The basic rule about the unilateral use of force in international relations is that such use is forbidden. The only exception is in the “inherent right of individual or collective self-defense if an armed attack occurs.” The term “armed attack” in this context means a “very serious onslaught” either on the territory of the injured state or on its agents or citizens, while they are at home or abroad, meaning in another state or in international waters or airspace. According to Article 51 of the U.N. Charter:

Nothing in the present Charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a Member of the United Nations, until the Security Council has taken measures necessary to maintain international peace and security. Measures taken by Members in the exercise of this right of self-defence shall be immediately reported to the Security Council and shall not in any way affect the authority and responsibility of the Security Council under the present Charter to take at any time such action as it deems necessary in order to maintain or restore international peace and security.

States have the right to resort to collective self-defense in the case of aggression by arms, subject to the request or consent of the victim of aggression. The collective self-defense measures do not affect or prejudice the possible operation of the U.N. security system. The U.N. security system may authorize states to take forceful measures against the wrongdoer if the U.N. Security Council concludes that a gross violation of international community obligations amounts to a threat to the peace, a breach of the peace, or an act of aggression. The U.N. Security Council takes over when it faces an international wrongful act that it deems that Article 39 of the U.N. Charter covers.

The U.N. Charter also sets a number of limits upon the right of self-defense, which Article 51 enshrines. This provision, which has developed into a provision of general international law, allows the use of force only in self-defense in order to repel an “armed attack,” and the defending State must immediately inform the Security Council of the action of using arms in self-defense. Article 51 envisages self-defense as a provisional measure by which the victim of an attack by force of arms may safeguard its rights until the security system, which centralizes this function, begins to work.

The basic deficiencies of the collective security system the U.N. Charter outlines include the assumption of continuing agreement among the permanent members of the United Nations Security CouncilSecurity Council: the United States, Russia, China, the United Kingdom, and France. This “P5” consensus was the basis for the proposal of a collective monopoly of force that they would hold accordingly. Dissent with the individual veto power that the U.N. Charter gives to each permanent member gives each the right to cripple the system. The Cold War gave the permanent members the incentive to exercise this veto against an adversary’s draft resolutions proposed under Chapter VII. Consequently, a distinguishing tendency to the present has emerged among states to engage in war under the cloak of “self-defense” without having to fear any decisive hindrance from the United Nations. In a number of cases, states have resorted to unilateral force under the cover of self-defense, protection of nationals abroad, or preemptive self-defense.

Military Achievement

The end of the Cold War (1945-1991);endCold War with the 1991 dissolution of the Soviet Union led to an increase in Great Power cooperation. The net result has been an increase in the number of peacekeeping operations, as well as in their size and complexity. The United Nations established only fifteen peacekeeping operations before 1988. Since then, the United Nations has established approximately forty such operations.

Two other critical features of peacekeeping operations are consent of the territorial state and impartiality. In some cases, peacekeeping has proceeded on the basis of a partial consent, meaning that peacekeeping forces have lacked the consent of one or more of the parties in the conflict. This situation has jeopardized the impartiality requirements of the operation. In 1992-1995, the United Nations Operation in SomaliaSomaliaU.N. Operation in Somalia (UNOSOM I) underwent a radical transformation through action by the Security Council, when UNOSOM I became UNOSOM II. The Security Council endowed UNOSOM II with enforcement powers under Chapter VII of the U.N. Charter (Resolution 814/1993). In Resolution 836 (June, 1993), the U.N. Security Council authorized the United Nations Protection ForceU.N. Protection Force (UNPROFOR) in the former Yugoslavia, “acting in self-defense, to take the necessary measures, including the use of force, to reply to bombardments against the safe areas by any of the parties.”

The United Nations deployed forces in all three cases where no peace existed to keep, that is, in situations of ongoing conflict within states and in which a partial or nearly total breakdown of governmental authorities had taken place. This trend in entrusting peacekeeping forces with enforcement functions has, however, undergone strong criticism–nor has it developed to the point of creating a special category of U.N. peace-enforcement units, which U.N. Secretary General Boutros-Ghali, BoutrosBoutros-Ghali, BoutrosBoutros Boutros-Ghali envisaged in 1992 in his “Agenda for Peace.”

On other occasions, the U.N. Security Council implicitly authorized regional or other organizations or arrangements to use force. The Security Council authorized, for example, maritime operations to enforce the embargo, as well as air operations to back up the peacekeeping forces (UNPROFOR) protecting safe areas. The implementation of the authorization was implicitly but obviously to occur through the West European Union (WEU) and the North Atlantic Treaty OrganizationNorth Atlantic Treaty Organization (NATO). The Security Council authorized NATO to establish a multinational force in Yugoslavia;formerBosnia-Herzegovina[Bosnia Herzegovina]Bosnia-Herzegovina, the Implementation Force (IFOR), which subsequently became the Stabilization Force (SFOR) after the end of the war in 1995. Its mandate was to ensure, if necessary by the use of force, the implementation of the General Framework Agreement for Peace in Bosnia and HerzegovinaDayton AgreementGeneral Framework Agreement for Peace in Bosnia and Herzegovina (Dayton Agreement).

Yugoslavia was the conflict with the greatest degree of complexity that the United Nations had confronted since the end of the Cold War. The developments in the following years of war in the former Yugoslavia included unsuccessful diplomatic efforts to end the conflict, including the Vance-Owen plan, the establishment by the Security Council of an International War Crimes Tribunal with the jurisdiction to prosecute crimes that had occurred in the violent conflict in the former Yugoslavia, and the authorization of member states by the Security Council in Resolution 816 in 1993 to take “all necessary measures in the airspace of the Republic of Bosnia and Herzegovina, in the event of further violation, to ensure compliance with the ban on flights.” On May 6, 1993, Security Council Resolution 824 declared the cities of Sarajevo, Tuzla, Zepa, Goraz̆de, and Bihać in Bosnia-Herzegovina as safe areas, after the United Nations declared Srebrenica and its surroundings as a safe area in Resolution 819 of April 16, 1993. Between April, 1994, and February, 1995, NATO airplanes conducted nine limited attacks against Serbian targets on the ground. In March, 1995, the Security Council decided on the replacement of UNPROFOR by three separate but interlinked peacekeeping operations in Bosnia-Herzegovina (UNPROFOR), Croatia (U.N. Confidence Restoration Operation, or UNCRO), and Macedonia (U.N. Preventative Deployment Force, or UNPREDEP).

U.S. M-1A1 Abrams tanks enter Bosnia in 1995 as part of a U.N. peacekeeping force that would allow the United Nations to focus on humanitarian issues.

(AP/Wide World Photos)

On August 28, 1995, thirty-eight people died in the Muslim part of Sarajevo, Bosnia-HercegovinaSarajevo by artillery fire, for which NATO held the Serbs responsible. This action led to Operation Deliberate Force (1995)Operation Deliberate Force on August 30, 1995, which lasted until September 14, 1995. It included heavy bombardment of troops, weapons, military installations, and production sites. The targets also included civilian traffic routes, intersections and bridges, and targets throughout the whole part of Bosnia-Herzegovina that the Serb forces controlled, going beyond the U.N. mandate to protect the safety zones.

The parties initialed the General Framework Agreement for Peace in Bosnia and HerzegovinaDayton AgreementGeneral Framework Agreement for Peace in Bosnia and Herzegovina on November 21, 1995, at a U.S. Air Force base near Dayton, Ohio. They signed this “Dayton Agreement” in Paris on December 14, 1995, with the five members of the “Contact Group” witnessing: the United States, Russia, France, Germany, and Britain. In accordance with the terms of the agreement, on December 15, 1995, the U.N. Security Council authorized the deployment of a 60,000-member multinational military Implementation Force (IFOR), having within it NATO and non-NATO forces, to replace UNPROFOR as of December 20, 1995, and to ensure compliance with the Dayton Agreement. Apart from the air strikes, in the case of Yugoslavia the Security Council was reluctant to back up by military sanctions the decisions it had taken under Chapter VII following the initial Resolution 713 of September 25, 1991.

The 1999 Kosovo crisis (1999)Kosovo crisis put this post-Cold War system, which the international community had consolidated, at significant risk. NATO decided to attack the Federal Republic of Yugoslavia (Serbia and Montenegro) without any Security Council authorization because of the massive gross violations of human rights by de facto and de jure state agents who were perpetrating them against the Kosovar population. The response of some commentators is that the Security Council, acting through Resolution 1244/1999 (adopted after the end of the war), endorsed NATO’s action ex post facto. A gradual alteration of the legal framework governing the use of force emerged as a consequence of the events of September 11, 2001, which focused world attention on terrorism. Which terrorist group had actually launched the attack was not clear on that day or for weeks afterward–nor was the answer clear as to whether or not one or more states had been instrumental in organizing and effecting the strike or at least harboring and assisting the terrorists.

The U.N. Security Council unanimously passed a resolution, 1368, on September 11, 2001, terrorist attacks;U.N. resolutionsSeptember 12, 2001. Its preamble “recognized” the right of individual and collective self-defense, plainly of the United States;and United Nations[United Nations]United Nations;and United States[United States]United States and other states willing to assist it, respectively. The resolution defined the terrorist acts of September 11 as a “threat to the peace” and, therefore, not as an “armed attack,” which would legitimize self-defense under Article 51. A later U.N. Security Council resolution, 1373, which it adopted on September 28, 2001, expressed the Security Council’s “readiness to take all the necessary steps to respond to the terrorist attacks . . . in accordance with its responsibility under the Charter of the United Nations.” The U.N. Security Council declared itself, thereby, to be ready to authorize military and other action, if necessary. This resolution wavered between the desire to take matters into its own hands, on one hand, and resignation to unilateral action by the United States, on the other. The ambiguity of the resolution probably stems to a large extent from the will of the United States to manage the crisis by itself, though with the possible assistance of states of its own choice. It wanted to do so without having to go through the U.N. Security Council and regularly report to it.

On the same day, relying on Article 5 of the NATO Statute, the North Atlantic Council unanimously adopted a statement providing for the right of collective self-defense in case of attack on one of the (then) nineteen members of the Alliance. The NATO member states opted to base their solution on U.N. Charter Article 51, thereby referring to the right of self-defense as the avenue rather than collective use of force under the authority of the Security Council.

Practically all states took an attitude that implied a considerable departure from the legal system on the use of force in the matter of a few days, to the effect of broadening the notion of self-defense. States came to assimilate action by a terrorist group amounting to a “threat to the peace” with aggression by force of arms, thereby entitling the victim state to resort to individual self-defense and third states to act in collective self-defense at the request of the former state. The events following September 11, 2001, allowed the victim state of terrorism to resort to a delayed response, undertaking self-defense use of force after some lapse of time. Classic legal doctrine on self-defense requires that the state react immediately to a specific aggressor state. The international community held as admissible that the United States could establish by its own judgment which state had harbored, supported, and assisted the terrorists. The United States thereby became itself accountable and a legitimate target of military reaction. The traditional U.N. Charter system of self-defense implied that the state acting in self-defense may strike only at a specific state or group of states–that is, the aggressor or aggressors. In other words, the victim state could not choose the target; the victim state was to respond immediately to an act of aggression.

On October 7, 2001, the United States, with the initial assistance of the United Kingdom, initiated military action against Afghanistan, which it termed Operation Enduring FreedomOperation Enduring Freedom. The United States alleged that its aim was to destroy the bases and infrastructure of the terrorist organization al-Qaeda in that country. It also intended to disrupt the incumbent Afghan authorities, the Taliban. The United States claimed that the Afghan authorities actively assisted, supported, and even used the terrorist organization. The United States invoked the right to individual self-defense, and the United Kingdom relied upon the right of collective self-defense. Both the United States and the United Kingdom claimed that they were responding to the terrorist attacks on the World Trade Center and the Pentagon, thereby acting to deter further terrorist attacks. The military action in Afghanistan lasted a few weeks. Only Iraq and Iran among the community of states openly and expressly challenged the legality of resort to force by the United States, with initial British help. Later, in a letter to the U.N. Security Council, the United States asserted its right to use force not only against Afghanistan but also against other organizations and countries that it claimed were supporting terrorism. Later, the United States mentioned Iran, Iraq, and North Korea. The United States acted forcibly through the United Nations in Iraq in 1990-1991, in Somalia in 1992, and in Bosnia-Herzegovina, 1992-1995, but when the U.N. support was not forthcoming, it acted through NATO in Kosovo in 1999. In other instances, the United States refrained from taking action because it did not have a sufficiently intense interest to intervene (Rwanda in 1994, Sierre Leone in 2000), or it engaged in military operations without any U.N. authorization (Iraq, 2003-2004).

Weapons, Uniforms, and Armor

National ground-force contingents participating in U.N. peacekeeping operations are typically characterized by their distinctive, white-painted armored vehicles, designed to facilitate their identification as a neutral force. Military personnel typically paint their helmets the distinctive U.N. sky blue. The United Nations also awards its own military decorations for meritorious service in peacekeeping operations.

Military Organization

The U.N. Security Council in 1999, voting to allow one more month for the Taliban, which controlled Afghanistan, to hand over Osama bin Laden for trial.

(AP/Wide World Photos)

The founders of the United Nations never envisaged the formation of an “army” that was to be at the disposal of the U.N. proper, exclusively dependent on the U.N. Security Council. Originally, the various member states were to place forces at the disposal of the Security Council as military contingents. Special agreements would determine the number and type of forces and their readiness. The U.N. Security Council would exercise its authority over national forces. These national forces would act under the strategic and military direction of the Security Council’s Military Staff Committee. The Charter did not envisage that a state sending a contingent would continue to exercise command and control over it, but by the same token it did not clearly exclude national control, leading to the dangerous possibility of a “dual allegiance” paralyzing these units. However, with the polarizing effect of the Cold War, the attempt at centralizing the use of force failed.

Doctrine, Strategy, and Tactics

The framers of the U.N. Charter envisaged a different Chapter VII regime governing the use of force in international relations other than the role that U.N. peacekeeping operations fulfill, just as the “authorizations regime” giving complete control to individual member states when using force to enforce the will of the U.N. Security Council also differs. Nevertheless, Chapter VII has become one of the most important U.N. tools, and often the only available one. According to Antonio Cassese (Italian jurist and first president of the International Criminal Tribunal for the former Yugoslavia), the international community universally recognizes it as consistent with the Charter.

U.N. peacekeepers with clearly marked vehicles drive toward Kibati in eastern Congo in November, 2008.

(AP/Wide World Photos)

The intent of peacekeeping operations is not actually to compel the parties to accept a solution that the U.N. imposes but rather to help put into practice, on the spot, the solution upon which the contending parties agree. U.N. peacekeepers can be very helpful in facilitating the fulfillment of complex peace processes in which the parties are willing to cooperate and build for the future. They of course must serve the first task of stopping the parties from fighting. They also, however, have come under criticism for being counterproductive, in that they freeze the situation without providing a real solution to the basic problems lying at the root of the conflict. An example of a successful U.N. peacekeeping operation includes the United Nations Interim Force in LebanonUnited Nations Interim Force in Lebanon (UNIFIL), which assisted in making possible, and less dangerous, the Israeli withdrawal from Lebanon in May and June of 2000. UNIFIL helped stabilize the situation there.

The notion of Anticipatory self-defenseanticipatory self-defense is a controversial one, with prominent legal scholars disputing and qualifying it. The main concern is that anticipatory self-defense becomes a justification for any use of force. Nuclear weapons, and arguably other forms of Weapons of mass destructionweapons of mass destruction (WMDs), have added a new dimension to this argument. Many reject the principle of anticipatory self-defense as legally valid, arguing that it has no legal basis in Article 51 of the U.N. Charter or in customary international law.

Contemporary Sources

For the U.N. report on the sequence of events and causes escalating to UNOSOM II combat with Somali militia, leading to numerous Somali and many UNOSOM II casualties in Mogadishu in 1993, see the “Report of the Commission of Inquiry Established Pursuant to Security Council Resolution 885 (1993) to Investigate Armed Attacks on UNOSOM II Personnel Which Led to Casualties Among Them” (U.N. Security Council, S/1994/653, June 1, 1994). For a U.N. summary and critical analysis of U.N. military peacekeeping operations in Bosnia and Herzegovina leading up to the Srebrenica massacre in the former Yugoslavia, see “Report of the Secretary-General Pursuant to General Assembly Resolution 53/35, the Fall of Srebrenica” (U.N. General Assembly, A/54/549, November 15, 1999). For a U.N. summary and critical analysis of U.N. peacekeeping operations in Rwanda, see “Report of the Independent Inquiry into the Actions of the United Nations During the 1994 Genocide” (U.N. Security Council, S/1999/1257, December 16, 1999). All U.N. Security Council resolutions are available at http://www.un.org/Docs/sc.United NationsInternational lawUnited Nations CharterUnited Nations peacekeeping operationsPeacekeeping operations, U.N.

Books and Articles
  • Cassese, Antonio. International Law. New York: Oxford University Press, 2005.
  • Falk, Richard A. The Costs of War: International Law, the U.N., and World Order After Iraq. New York: Routledge, 2008.
  • Lowe, Vaughan, et al., eds. The United Nations Security Council and War: The Evolution of Thought and Practice Since 1945. New York: Oxford University Press, 2008.
  • Malone, David M., ed. The U.N. Security Council: From the Cold War to the Twenty-first Century. Boulder, Colo.: Lynne Rienner, 2004.
  • Silber, Laura, and Allan Little. Yugoslavia: Death of a Nation. New York: Penguin, 1996.
Films and Other Media
  • Black Hawk Down. Feature film. Columbia, 2001.
  • Crisis in Kosovo. Documentary. ABC News, 1999.
  • Ghosts of Rwanda. Documentary. Public Broadcasting Service, 2004.
  • Hotel Rwanda. Feature film. Lions Gate Entertainment, 2004.
  • The Peacekeepers. Documentary. BFS Entertainment, 2005.
  • Sometimes in April. Television film. HBO Films, 2005.
  • Welcome to Sarajevo. Feature film. Miramax, 1997.
  • Yugoslavia: Death of a Nation. Documentary. Discovery Channel, 1996.

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