Aggressive War

A war of aggression, sometimes also war of conquest, is a military conflict waged without the justification of self-defense, usually for territorial gain and subjugation, in contrast with the concept of a just war.

Wars without international legality (i.e. not out of self-defense nor sanctioned by the United Nations Security Council) can be considered wars of aggression; however, this alone usually does not constitute the definition of a war of aggression; certain wars may be unlawful but not aggressive (a war to settle a boundary dispute where the initiator has a reasonable claim, and limited aims, is one example).

In the judgment of the International Military Tribunal at Nuremberg, which followed World War II, "War is essentially an evil thing. Its consequences are not confined to the belligerent states alone, but affect the whole world. To initiate a war of aggression, therefore, is not only an international crime; it is the supreme international crime differing only from other war crimes in that it contains within itself the accumulated evil of the whole."
Article 39 of the United Nations Charter provides that the UN Security Council shall determine the existence of any act of aggression and "shall make recommendations, or decide what measures shall be taken in accordance with Articles 41 and 42, to maintain or restore international peace and security".The Rome Statute of the International Criminal Court refers to the crime of aggression as one of the "most serious crimes of concern to the international community", and provides that the crime falls within the jurisdiction of the International Criminal Court (ICC). However, the Rome Statute stipulates that the ICC may not exercise its jurisdiction over the crime of aggression until such time as the states parties agree on a definition of the crime and set out the conditions under which it may be prosecuted. At the Kampala Review Conference on 11 June 2010, a total of 111 State Parties to the Court agreed by consensus to adopt a resolution accepting the definition of the crime and the conditions for the exercise of jurisdiction over this crime. The relevant amendments to the Statute entered into force on July 17, 2018 after being ratified by 35 States Parties.

Possibly the first trial for waging aggressive war is that of the Sicilian king Conradin in 1268.

Definitions

The origin of the concept, the author Peter Maguire argues, emerged from the debate on Article 231 of the Treaty of Versailles of 1919: "Germany accepts the responsibility of Germany and her allies for causing all the loss and damage to which the Allied and Associated Governments and their nationals have been subjected as a consequence of the war imposed upon them by the aggression of Germany and her allies." Maguire argues:

The Japanese invasion of Manchuria had a significant negative effect on the moral strength and influence of the League of Nations. As critics had predicted, the League was powerless if a strong nation decided to pursue an aggressive policy against other countries, allowing a country such as Japan to commit blatant aggression without serious consequences. Adolf Hitler and Benito Mussolini were also aware of this, and ultimately both followed Japan's example in aggression against their neighbors: in the case of Italy, against Ethiopia (1935–1937) and Albania (1939); and Germany, against Czechoslovakia (1938–1939) and Poland (1939).

In November 1935, the League of Nations condemned Italy's aggression in Ethiopia and imposed economic sanctions. The prominent jurist Hans Kelsen argued that in the Ethiopian case, the League had "at least made certain efforts to fulfill its duty in the cases of illegal aggression undertaken by member states against other member states."

The Convention for the Definition of Aggression

Two Conventions for the Definition of Aggression were signed in London on 3 and 4 July 1933. The first was signed by Czechoslovakia, Romania, the Soviet Union, Turkey and Yugoslavia, and came into effect on 17 February 1934, when it was ratified by all of them but Turkey. The second was signed by Afghanistan (ratified 20 October 1933), Estonia (4 December), Latvia (4 December), Persia (16 November), Poland (16 October), Romania (16 October), the Soviet Union (16 October) and Turkey, which ratified both treaties on 23 March 1934. Finland acceded to the second convention on 31 January 1934. The second convention was the first to be registered with the League of Nations Treaty Series on 29 March 1934, while the first was registered on 26 April. As Lithuania refused to sign any treaty including Poland, it signed the definition of aggression in a separate pact with the Soviet Union on 5 July 1933, also in London, and exchanged ratifications on 14 December. It was registered in the Treaty Series on 16 April 1934.

The signatories of both treaties were also signatories of the Kellogg–Briand Pact prohibiting aggression, and were seeking an agreed definition of the latter. Czechoslovakia, Romania and Yugoslavia were members of the Little Entente, and their signatures alarmed Bulgaria, since the definition of aggression clearly covered its support of the Internal Macedonian Revolutionary Organization. Both treaties base their definition on the "Politis Report" of the Committee of Security Questions made 24 March 1933 to the Conference for the Reduction and Limitation of Armaments, in answer to a proposal of the Soviet delegation. The Greek politician Nikolaos Politis was behind the inclusion of "support for armed bands" as a form of aggression. Ratifications for both treaties were deposited in Moscow, as the convention was primarily the work of Maxim Litvinov, the Soviet signatory. The convention defined an act of aggression as follows:
* Declaration of war upon another State.
* Invasion by its armed forces, with or without a declaration of war, of the territory of another State.
* Attack by its land, naval or air forces, with or without a declaration of war, on the territory, vessels or aircraft of another State.
* Naval blockade of the coasts or ports of another State.
* Provision of support to armed bands formed in its territory which have invaded the territory of another State, or refusal, notwithstanding the request of the invaded State, to take, in its own territory, all the measures in its power to deprive those bands of all assistance or protection.

The League prerogative under that convention to expel a League member found guilty of aggression was used by the League Assembly only once, against the Soviet government itself, on December 14, 1939, following the Soviet invasion of Finland.

Primary documents:
Text of the Convention of 3 July

The Nuremberg Principles

In 1945, the London Charter of the International Military Tribunal

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