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in Dinah Sehlton (ed), Encyclopedia of Genocide, Macmillan 2004, Vol. I, pp. 11-16.

The human cost of armed conflict is such that international law qualifies aggression as the gravest crime possible, far more serious than the war crimes that ensue during armed conflict. The United Nations was founded “to save succeeding generations from the scourge of war” (preamble), and article 1, paragraph 1, of the Charter establishes its mandate “to maintain international peace and security, and to that end: to take effective collective measures for the prevention and removal of threats to the peace, and for the suppression of acts of aggression…” Article 2, paragraph 3, imposes an obligation to negotiate “All members shall settle their international disputes by peaceful means” and article 2, paragraph 4, specifically engages States to “refrain in their international relations from the threat or use of force”.

This prohibition of force has been repeated in countless resolutions of the Security Council and of the General Assembly, most importantly in GA Resolution 2625 (XXV) of October 24, 1970, Resolution on Principles of International Law concerning Friendly Relations and Co-operation among States in accordance with the Charter of the United Nations , which solemnly proclaims that “Every State has the duty to refrain in its international relations from the threat or use of force against the territorial integrity or political independence of any State, or in any other manner inconsistent with the purposes of the United Nations. Such a threat or use of force constitutes a violation of international law and the Charter of the United Nations and shall never be employed as a means of settling international issues. A war of aggression constitutes a crime against the peace, for which there is responsibility under international law. In accordance with the purposes and principles of the United Nations, States have the duty to refrain from propaganda for wars of aggression.” This obligation is also stipulated in article 20 of the International Covenant on Civil and Political Rights: “Any propaganda for war shall be prohibited by law.”

Thus, aggression is not only an internationally wrongful act giving rise to State responsibility and the obligation to make reparation, it is also an international crime giving rise to personal criminal liability.

Prior to the first world war, aggression had not yet been declared to be an international crime and war was still perceived as a legitimate means of achieving political objectives. The human catastrophe of the first world war (“the war to end all wars”) leaving ten million deaths in its wake, led to the creation of the League of Nations (predecessor of the United Nations) and many countries sought to devise ways to ban war as an exercise of State sovereignty. On August 27, 1928 at Paris the Kellogg-Briand Pact was signed, spearheaded by the U.S. Secretary of State Frank Kellogg, the French Minister of Foreign Affairs Aristide Briand and the German Minister of Foreign Affairs Gustav Stresemann. By virtue of article I, the forty-five States parties “condemn recourse to war for the solution of international controversies, and renounce it, as an instrument of national policy”; in article II they “agree that the settlement or solution of all disputes or conflicts of whatever nature or of whatever origin they may be … shall never be sought except by pacific means”. As a corollary to the Pact, a subsequent American Secretary of State Henry Stimson enunciated the doctrine of non-recognition of international territorial changes effected by force. This doctrine was a response to Japan's unilateral seizure of Manchuria in September, 1931, and was was subsequently reflected in several international declarations, including a League of Nations resolution of March 11, 1932, the Inter-American Pact of Rio de Janeiro of October 10, 1933, and the Budapest Articles of Interpretation (September 10, 1934) to the Kellogg-Briand Pact.

Alas, this first international movement to ban war did not prevent the outbreak of the second world war, that would take 50 million lives, five times as many as the first conflagration. Hitler was the principal but not the only aggressor. The Soviet Union, for instance, aggressed Poland in September 1939, together with Germany, pursuant to a secret treaty signed by foreign Ministers Ribbentrop and Molotov, in which they divided Poland among themselves. In October 1939 the Soviet Union aggressed the three Baltic States, Estonia, Latvia and Lithuania, occupied and annexed them; in November 1939, it aggressed Finland, robbed it of 18,000 square miles of territory and forced 450,000 Finns to resettle elsewhere. For the latter aggression the Soviet Union was formally expelled from the League of Nations in December 1939.

Following German capitulation in May 1945, the Allies adopted the London Agreement of August 8, 1945 which contained the Charter of the Nuremberg Tribunal. Article 6 (a) of this charter provided for a new category of crime in international law, crimes against peace: “namely, planning, preparation, initiation or waging of a war of aggression, or a war in violation of international treaties, agreements or assurances, or participation in a Common Plan or Conspiracy for the accomplishment of any of the foregoing”.

Although this constituted undoubtedly an ex post facto penal law, as noted by U.S. Chief Justice Harlan Stone and by Justice William O. Douglas (Douglas, An Almanac of History , 1954), many Nazis were indicted and convicted of this offence, including Goering, Hess, von Ribbentrop, Keitel, Rosenberg, Frick, Funk, Jodl, Seyss-Inquart, von Neurath, Raeder and Dönitz, seven of whom were also sentenced to death.

By virtue of General Assembly Resolution 95(1) of December 11, 1946, the Nuremberg judgment, including the condemnation of aggression, was recognized as binding international law, and the International Law Commission was entrusted with drafting what became known as the “Nuremberg Principles”, which were adopted in July 1950, including the definition of the crime against peace. In General Assembly Resolution 177 (II) of November 21 1947, the International Law Commission was mandated to prepare a code on offences against the peace and security of mankind. After nearly forty years of work and continuous consultation with States, the International Law Commission adopted in 1996 a “Draft Code on Crimes Against the Peace and Security of Mankind”. Article 16 of the draft code contains the following statutory definition of the crime of aggression: “ An individual who, as leader or organizer, actively participates in or orders the planning, preparation, initiation or waging of aggression committed by a State shall be responsible for a crime of aggression”. The ILC's draft code, however, has not yet been proclaimed by the General Assembly.

Statute of the International Criminal Court

More recently the Diplomatic Conference of Rome adopted on July 18, 1998 the Statute of the International Criminal Court, which defines the jurisdiction of the Court in its article 5, including with respect to the crime of aggression. Paragraph 2 of article 5, however, stipulates: “The Court shall exercise jurisdiction over the crime of aggression once a provision is adopted in accordance with articles 121 and 123 defining the crime and setting out the conditions under which the Court shall exercise jurisdiction with respect to his crime.” This delay in the exercise of the Court's competence with regard to aggression is primarily attributable to the opposition of the United States. However, since the United States, which originally had signed the statute, has indicated that it will not ratify it, the assembly of States parties to the Rome Statute is now free to adopt a definition consistent with the judgment of the Nuremberg trials and with General Assembly Resolution 3314 (XXIX) of December 14, 1974, which provides in article 1:

“Aggression is the use of armed force by a State against the sovereignty, territorial integrity or political independence of another State, or in any other manner inconsistent with the Charter of the United Nations”. Article 2 stipulates: “The first use of armed force by a State in contravention of the Charter shall constitute prima facie evidence of an act of aggression although the Security Council may, in conformity with the Charter, conclude that a determination that an act of aggression has been committed would not be justified in the light of other relevant circumstances, including the fact that the acts concerned or their consequences are not of sufficient gravity.”

Definition according to General Assembly Resolution 3314

Article 3 stipulates:

“any of the following acts, regardless of a declaration of war, shall subject to and in accordance with the provisions of article 2, qualify as an act of aggression:

•  The invasion or attack by the armed forces of a State of the territory or another State, or any military occupation, however temporary, resulting from such invasion or attack, or any annexation by the use of force of the territory of another State or part thereof,

•  Bombardment by the armed forces of a State against the territory of another State or the use of any weapons by a State against the territory of another States;

•  The blockade of the ports or coasts of a State by the armed forces of another States;

•  an attack by the armed forces of a State on the land, sea or air forces, or marine and air fleets of another States;

•  the use of armed forces of one State which are within the territory of another State with the agreement of the receiving States, in contravention of the conditions provided for in the agreement or any extension of their presence in such territory beyond the termination of the agreement;

•  the action of a State in allowing its territory, which it has placed at the disposal of another States, to be used by that other State for perpetrating an act of aggression against a third State;

•  the sending by or on behalf of a State of armed bands, groups, irregulars or mercenaries, which carry out acts of armed force against another State of such gravity as to amount to the acts listed above, or its substantial involvement therein.

Article 5 warns that “no consideration of whatever nature, whether political, economic, military or otherwise may serve as a justification for aggression. A war of aggression is a crime against international peace. Aggression gives rise to international responsibility. No territorial acquisition or special advantage resulting from aggression is or shall be recognized as lawful.”

Article 7 explains, however, that “nothing in this declaration … could in any way prejudice the right to self-determination, freedom and independence, as derived from the Charter, of persons forcibly deprived of that right and referred to in the Declaration on Principles of International Law concerning Friendly Relations and Cooperation among States in accordance with the Charter of the United Nations, particularly peoples under colonial and racist regimes or other forms of alien domination, nor the right of these peoples to struggle to that end and to seek and receive support, in accordance with the principles of the Charter and in conformity with the above-mentioned Declaration.”

The UN General Assembly has reaffirmed the consensus definition in several declarations, including the Declaration on International Détente (Res.32/155 (1977)) the Declaration of Societies for Life in Peace (Res. 33/73 (1978)), the Declaration on the Non-Use of Force (Res. 42/22 (1988).

Unexplainably, the Security Council has avoided making reference to the consensus definition. Even in a case as clear as the 1990 aggression of Kuwait by Iraq, the Security Council condemned it merely as an “invasion and illegal occupation” (Res. 674/1990), decided that “the annexation of Kuwait by Iraq under any form and whatever pretext has no legal validity, and is considered null and void” (Res. 662 (1990), however no reference was made to the application of article 3(a) of the of the definition of aggression or to the penal consequences pursuant to article 5.

Nevertheless, the language of the declaration deserves general reflection, bearing in mind that since the second world war there have been many armed conflicts and many instances of aggression. Such wars ought to be measured against the standards laid down by the UN Charter, the Nuremberg Principles and the Declaration on the Definition of Aggression. It is worth examining whether the colonial wars were compatible with article 2, paragraph 4, of the Charter? How are we to judge the Dutch “police actions” in Indonesia (1947-50), the French Indochina wars (1952-54), the French-Algerian conflict (1954-63)? Who was the aggressor in the Korean war ? In the Indian-Pakistani war 1970-71 ? How should we evaluate the Warsaw Pact's invasion of Czechoslovakia in 1968, and the Soviet Union's occupation of Afghanistan in 1980? Was there a clear aggressor in the Six-day's war of 1967 ? How are the daily incursions of Israel in Gaza and the Occupied Palestine territories to be evaluated ? Were the military actions of Israel in Lebanon 2006 justified in international law? Who was the aggressor in the Iraq-Iran War 1980-1990 ? How is the Turkish invasion of Cyprus in 1974 and subsequent occupation of Northern Cyprus to be rated ? The U.S.-led invasion of Cuba, in 1961, its involvement in the Vietnam War, including the saturation bombing of North and South Vietnam, Laos and Cambodia ? The U.S. invasion of Grenada (1983), the military and paramilitary activities in Nicaragua (1983-86), the invasion of Panama (1989), the U.S. war on Afghanistan (2001) and on Iraq (2003) ? How are we to judge the use of force in the territory of other countries, e.g. the sinking of the Greenpeace vessel “Rainbow Warrior” in Auckland Harbour in New Zealand by French special forces in 1985?The list could be continued.

Impunity, People's Tribunals

Impunity in international law remains a thorny issue. The UN General Assembly, the Commission on Human Rights, and the Human Rights Committee, among others, have repeatedly condemned impunity for the crime of aggression, war crimes and crimes against humanity, but there is no mechanism to punish aggressors, and the historical experience has been that aggressors go unpunished unless they are totally defeated and must accept unconditional surrender. For this reason it is worth recalling that, at the opening of the Nuremberg Trials, United States chief prosecutor Robert Jackson stated:

“We must never forget that the record on which we judge these defendants today is the record on which history will judge us tomorrow… While this law is first applied against German aggressors, the law includes, and if it is to serve a useful purpose it must condemn, aggression by any other nations, including those which sit here now in judgment” (IMT Vol. 2, November 21, 1945, p. 101)

Sixty years after Jackson's admonition, the principle deserves our attention more than ever. None of the Special Tribunals created since have jurisdiction over the crime of aggression, not the International Tribunal for the Former Yugoslavia, not the International Tribunal for Rwanda, not the Iraqi Special Tribunal. Precisely because no international tribunal has been given competence to try aggressors for the crime of aggression, a number of representatives of civil society have organised “People's Tribunals”, notably the Russell Tribunal on the Vietnam War, organised by British pacifist Bertrand Russell and French philosopher Jean Paul Sartre (held 1967 in Sweden and Denmark) and the Brussels Tribunal on the Iraq War organized by former Attorney General Ramsey Clark (April 2004), with the participation of two ex-United Nations humanitarian coordinators for Iraq, Dennis Halliday and Hans von Sponeck. Both tribunals condemned the United States as an aggressor in Vietnam and as an aggressor in Iraq. There is also a “Permanent People's Tribunal” (Fondation Internationale Lelio Basso), which has held more than 30 sessions, one of them in Paris in 1984, devoted to the genocide against the Armenians, and one held in Rome in 2002 devoted to international law and the new wars of aggression.

Justifications for the use of force, self-defence

There are, of course justifications for the use of force, which are legitimate according to international law. Article 51 of the UN Charter stipulates: “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.” The application of this provision is, however, strictly limited by the over-all obligation to negotiate set forth in article 2, paragraph 3, and the prohibition of the threat of or the use of force in article 2, paragraph 4, of the UN Charter. In his address to the General Assembly on September 23, 2003, Secretary General Kofi Annan stated: “Article 51 of the Charter prescribes that all states, if attacked, retain the inherent right of self-defence… until now it has been understood that when states go beyond that, and decide to use force to deal with broader threats to international peace and security, they need the unique legitimacy provided by the United Nations.”The International Court of Justice has specified the situations in which article 51 can be invoked, most recently in the advisory opinion of 9 July 2004. The consensus of international law experts is that preventive or pre-emptive war is not compatible with article 51 of the charter, which requires an existing “armed attack” and places overall responsibility on the Security Council.

Humanitarian intervention is another possible justification for the use of force, and it remains the responsibility of the Security Council to legitimise or not a given military intervention. Approval was, for example, given in Resolution 688 of April 5, 1991 with respect to the necessity to create safety zones for Kurds and other minorities in Iraq. Humanitarian intervention would also have been possible in order to stop the genocide in Cambodia (1975-79) or in Rwanda (1994). While humanitarian intervention may be an international duty in order to stop genocide and crimes against humanity, it must not become a cloak or an excuse for military interventions responding to other political agendas. For instance, Human Rights Watch recently conducted a study of the arguments advanced by the United States as justification for the war on Iraq 2003, and concluded that the U.S. intervention did not satisfy the constitutive elements of a humanitarian intervention.

A human right to peace

The international prohibition of aggression may also be viewed from the aspect of a human right to peace. Indeed, among the so-called third generation rights, the right to peace is paramount, because, unless humanity enjoys peace, it cannot exercise its first and second generation rights, namely its civil, political, economic, social and cultural rights.

On 12 November 1984 the United Nations General Assembly adopted Resolution 39/11 annexing the Declaration on the Right of Peoples to Peace, which reaffirms “that the principal aim of the United Nations is the maintenance of international peace and security” and the “aspirations of all peoples to eradicate war from the life of mankind and, above all, to avert a world-wide nuclear catastrophe”. By virtue of operative paragraph 2, the declaration proclaims “that the preservation of the right of peoples to peace and the promotion of its implementation constitute a fundamental obligation of each State.” In paragraph 3, the declaration “demands that the policies of States be directed towards the elimination of the threat of war, particularly nuclear war, the renunciation of the use of force in international relations and the settlement of international disputes by peaceful means.”

This declaration has been reaffirmed in countless resolutions of the General Assembly and of the United Nations Commission on Human Rights. In its resolution 2002/71 of 25 April 2002, the Commission links the right to peace with the right to development, affirms “that all States should promote the establishment, maintenance and strengthening of international peace and security and, to that end, should do their utmost to achieve general and complete disarmament under effective international control, as well as to ensure that the resources released by effective disarmament measures are used for comprehensive development, in particular that of the developing countries” and urges “the international community to devote part of the resources made available by the implementation of disarmament and arms limitation agreements to economic and social development, with a view to reducing the widening gap between developed and developing countries.”


In a world of weapons of mass destruction, it is imperative to strengthen the early arning and peaceful settlement mechanisms of the United Nations. In view of the human consequences of war, aggression must be prevented through international solidarity. The idea is that no country can take the law in its own hands. The United Nations is there to facilitate negotiation. Force can only be used as a last resort and only with approval of the Security Council. Meanwhile it would be desirable that the Conference of States Parties to the Statute of the International Criminal Court agrees as soon as possible on a definition of aggression, so as to make article 5 of the statute operative. Thus a measure of deterrence would be achieved if all potential aggressors know that one day they may find themselves before the tribunal. For the sake of the survival of the human species, the human rights to peace must be protected not only by tribunals and norms, but by education toward a culture of peace.


Bassiouni, M. Cherif, The Statute of the International Criminal Court. A Documentary History (1998). Transnational Publishers, New York.

Broms, B. « The Definition of Aggression », in Recueil des Cours de l'Académie de Droit Internationale vol. 154 (1977 I) pp. 299-399.

Cassin V. et al, The Definition of Aggression, 16 Harvard International Law Journal, (1975) pp. 598-613.

Dinstein, Yoram. War, Aggression and Self-Defence , 2d. ed. (1994), Cambridge.

Fastenrath, Ulrich, “Definition of Aggression” in H. Volger (ed.) A Concise Encyclopedia of the United Nations (2002). Kluwer Law International, The Hague, pp. 11-14..

Ferencz,. Benjamin. Defining International Aggression. The Search for World Peace, A Documentary Analysis, 2 vols. (1975).

Ferencz, Benjamin. “Aggression”, in R. Bernhardt (ed) Encyclopaedia of Public International Law, vol. 1 (1 992) pp. 58-65.

Roth, Kenneth, “War in Iraq: Not a Humanitarian Intervention” (2004). Human Rights Watch, New York.

Schwebel, S.M. “Aggression, Intervention and Self-Defence in Modern International Law”, in Recueil des Cours vol. 139 (1972 II) pp. 411-497.

© Alfred de Zayas

Institut Universitaire de Hautes Etudes Internationales, Geneva

Academie internationale de Droit Constitutionnel, Tunis

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