A declaration of war is a formal act by which one state announces existing or impending war activity against another. The declaration is a performative speech act (or the public signing of a document) by an authorized party of a national government, in order to create a state of war between two or more states.
The legality of who is competent to declare war varies between nations and forms of government. In many nations, that power is given to the head of state or sovereign. In other cases, something short of a full declaration of war, such as a letter of marque or a covert operation, may authorise war-like acts by privateers or mercenaries. The official international protocol for declaring war was defined in the Hague Convention (III) of 1907 on the Opening of Hostilities.
Since 1945, developments in international law such as the United Nations Charter, which prohibits both the threat and the use of force in international conflicts, have made declarations of war largely obsolete in international relations,[1] though such declarations may have relevance within the domestic law of the belligerents or of neutral nations. The UN Security Council, under powers granted in articles 24 and 25, and Chapter VII of the Charter, may authorize collective action to maintain or enforce international peace and security. Article 51 of the United Nations Charter also states that: "Nothing in the present Charter shall impair the inherent right to individual or collective self-defence if an armed attack occurs against a state."[2]
Declarations of war have been exceedingly rare since the end of World War II.[3] [4] Scholars have debated the causes of the decline, with some arguing that states are trying to evade the restrictions of international humanitarian law (which governs conduct in war) while others argue that war declarations have come to be perceived as markers of aggression and maximalist aims.
The practice of declaring war has a long history. The ancient Sumerian Epic of Gilgamesh gives an account of it,[5] as does the Old Testament.[6] [7] The Roman Republic formalized the declaration of war by a special ceremony, the ritual of the Fetials, though the practice started to decline into the Imperial era.
However, the practice of declaring war was not always strictly followed. In his study Hostilities without Declaration of War (1883), the British scholar John Frederick Maurice showed that between 1700 and 1870 war was declared in only 10 cases, while in another 107 cases war was waged without such declaration (these figures include only wars waged in Europe and between European states and the United States, not including colonial wars in Africa and Asia).
In modern public international law, a declaration of war entails the recognition between countries of a state of hostilities between these countries, and such declaration has acted to regulate the conduct between the military engagements between the forces of the respective countries. The primary multilateral treaties governing such declarations are the Hague Conventions.
The League of Nations, formed in 1919 in the wake of the First World War, and the General Treaty for the Renunciation of War of 1928 signed in Paris, France, demonstrated that world powers were seriously seeking a means to prevent the carnage of another world war. Nevertheless, these powers were unable to stop the outbreak of the Second World War, so the United Nations was established following that war in a renewed attempt to prevent international aggression through declarations of war.
In classical times, Thucydides condemned the Thebans, allies of Sparta, for launching a surprise attack without a declaration of war against Plataea, Athens' ally – an event that began the Peloponnesian War.[8]
The utility of formal declarations of war has always been questioned, either as sentimental remnants of a long-gone age of chivalry or as imprudent warnings to the enemy. For example, writing in 1737, Cornelius van Bynkershoek judged that "nations and princes endowed with some pride are not generally willing to wage war without a previous declaration, for they wish by an open attack to render victory more honourable and glorious."[9] Writing in 1880, William Edward Hall judged that "any sort of previous declaration therefore is an empty formality unless the enemy must be given time and opportunity to put himself in a state of defence, and it is needless to say that no one asserts such a quixotism to be obligatory."[10]
See main article: Declarations of war during World War I.
See main article: Declarations of war during World War II.
Declarations of war, while uncommon in the traditional sense, have mainly been limited to the conflict areas of the Western Asia and East Africa since 1945. Additionally, some small states have unilaterally declared war on major world powers such as the United States or Russia when faced with a hostile invasion and/or occupation. The following is a list of declarations of war (or the existence of war) by one sovereign state against another since the end of World War II in 1945. Only declarations that occurred in the context of a direct military conflict are included.
| War(s) | Date | Titled | Belligerents | Ended | References | |
|---|---|---|---|---|---|---|
| Declaring party | Opponent | |||||
| 15 May 1948 | Declaration of war | Egypt |  Israel | 26 March 1979 | [11] | |
 Jordan | 26 October 1994 | |||||
Syria, Iraq,  Lebanon | Still technically at war | |||||
| Six-Day War (1967) | June 1967 | Declaration of war |  Mauritania | 1991 | [12] | |
| Ogaden War | 13 July 1977 | Declaration of war |  Somalia |  Ethiopia | 15 March 1978 | |
| Uganda–Tanzania War | 2 November 1978 | Declaration of war |  Uganda | 3 June 1979 | [13] | |
| Iran–Iraq War | 22 September 1980 | Declaration of war |  Iraq | 20 July 1988 | [14] | |
| United States invasion of Panama | 15 December 1989 | Existence of a state of war |  Panama |  United States | 31 January 1990 | [15] |
| Eritrean–Ethiopian War | 14 May 1998 | Existence of a state of war | Ethiopia |  Eritrea | 12 December 2000 | [16] |
| Chadian Civil War | 23 December 2005 | Existence of a state of war |  Chad |  Sudan | 15 January 2010 | [17] |
| Djiboutian–Eritrean border conflict | 13 June 2008 | Existence of a state of war |  Djibouti | Eritrea | 6 June 2010 | [18] |
| Russo-Georgian War | 9 August 2008 | Existence of a state of war |  Georgia | 16 August 2008 | [19] | |
| Heglig Crisis | 11 April 2012 | Existence of a state of war | Sudan | 26 May 2012 | [20] | |
| Anglophone Crisis | 4 December 2017 | Declaration of war | Still at war | [21] | ||
| Second Nagorno-Karabakh War | 27 September 2020 | Existence of a state of war |  Azerbaijan |  Armenia | 10 November 2020 | [22] |
| Second Western Sahara War | 14 November 2020 | Declaration of war |  Morocco | Still at war | [23] | |
| Russian invasion of Ukraine | 22 March 2024 | Existence of a state of war | [24] | |||
No formal declaration of war has been issued in the ongoing Russo-Ukrainian War. At the beginning of the Russian invasion of Ukraine, Putin gave a televised broadcast announcing the start of the invasion with the term "special military operation", side-stepping a formal declaration of war.[25] The statement was, however, regarded as a declaration of war by the Ukrainian government[26] and reported as such by many international news sources.[27] [28] While the Ukrainian parliament refers to Russia as a "terrorist state" in regards to its military actions in Ukraine,[29] it has not issued a formal declaration of war on its behalf.
In Title II, Article 2 of the first Hague Convention of 1899, the signatory states agreed that at least one other nation be used to mediate disputes between states before engaging in hostilities:
The Hague Convention (III) of 1907 called "Convention Relative to the Opening of Hostilities"[30] gives the international actions a country should perform when opening hostilities. The first two Articles say:
In an effort to force nations to resolve issues without warfare, framers of the United Nations Charter attempted to commit member nations to using warfare only under limited circumstances, particularly for defensive purposes.
The UN became a combatant itself after North Korea invaded South Korea on 25 June 1950, which began the Korean War. The UN Security Council condemned the North Korean action by a 9–0 resolution (with the Soviet Union absent) and called upon its member nations to come to the aid of South Korea. The United States and 15 other nations formed a "UN force" to pursue this action. In a press conference on 29 June 1950, US President Harry S. Truman characterized these hostilities as not being a "war" but a "police action".[31]
The United Nations has issued Security Council Resolutions that declared some wars to be legal actions under international law, most notably Resolution 678, authorizing the 1991 Gulf War which was triggered by Iraq's invasion of Kuwait. UN Resolutions authorise the use of "force" or "all necessary means".[32] [33]
The legality of who is competent to declare war varies between nations and forms of government. In many nations, that power is given to the head of state or sovereign. The official international protocol for declaring war was defined in the Hague Convention (III) of 1907 on the Opening of Hostilities.
Since 1945, developments in international law such as the United Nations Charter, which prohibits both the threat and the use of force in international conflicts, have made declarations of war largely obsolete in international relations, though such declarations may have relevance within the domestic law of the belligerents or of neutral nations. The UN Security Council, under powers granted in articles 24 and 25, and Chapter VII of the Charter, may authorize collective action to maintain or enforce international peace and security. Article 51 of the United Nations Charter also states that: "Nothing in the present Charter shall impair the inherent right to individual or collective self-defence if an armed attack occurs against a state."[2]
Declaring war is usually done through a process that involves prior approval before a formal announcement is made. This differs by country as some do not have a pre-approved process, and a given head of government can declare war with no pre-conditions.
| scope=col | Country | scope=col | War declarer | scope=col | Legal cause | scope=col | Authorized by | scope=col | Additional information |
|---|---|---|---|---|---|---|---|---|---|
| scope=row | Australia | Prime Minister | Section 61 of the Australian constitution | Prime Minister | Per Defence Act 1903[34] a declaration of war may be made by the Prime Minister of Australia alone. | ||||
| scope=row | Brazil | President | Article 84 of the Brazilian constitution | Congress | The President of Brazil has the power to declare war, in the event of foreign aggression, when authorized by the National Congress or, upon its ratification if the aggression occurs between legislative sessions, and decree full or partial national mobilization under the same conditions. | ||||
| scope=row | Canada | Monarch | None | Monarch (de jure) | See: Declaration of war by Canada. | ||||
| scope=row | China | President | Article 62(15), 67(19) and 80 | Congress (de jure) | The National People's Congress is vested with the power to decide "on issues concerning war and peace" while the President "in pursuance of the decisions of the National People's Congress...proclaims a state of war." The Standing Committee of the National People's Congress may "decide, when the National People's Congress is not in session, on the proclamation of a state of war in the event of an armed attack on the country or in fulfillment of international treaty obligations concerning common defense against aggression". | ||||
| scope=row | Finland[35] | President | Article 93 of the Finnish constitution | Parliament | The President of Finland may declare war or peace, with permission from the Parliament of Finland | ||||
| scope=row | France | Government | Article 35 of the French constitution | Parliament | The Parliament "authorize" the declaration of war.[36] Both the National Assembly and the Senate does not vote on the declaration, but only debate on the proposal of the government. After 4 months of any military intervention, the Parliament can authorize the extension of the war. The 4 months period is not always respected by the government.[37] | ||||
| scope=row | Germany[38] | Parliament | Article 115a GG | Parliament | Unless Germany is attacked by an opposing military force, a two-thirds majority vote must be held in the Bundestag if the federal republic is under the threat of war. | ||||
| scope=row | Hungary[39] | Parliament | Article 49 of the Fundamental Law of Hungary | Parliament | |||||
| scope=row | India | President | Article 53(2) of the Constitution of India | Parliament | The president of India can declare war or conclude peace, subject to the approval of parliament and advice from select government officials.[40] | ||||
| scope=row | Israel | Prime Minister | The Knesset:Article 40(a)[41] and The Government:Article 3(a)[42] of the Basic Laws of Israel | Prime Minister | Per article 40(a) of the Basic Law The Knesset, the state will declare war "pursuant to a government decision" with the prime minister to give notice to the Knesset "as soon as possible." Per article 3(a) of the Basic Law The Government, "the Government is the Prime Minister and Ministers." | ||||
| scope=row | Kuwait | Monarch | Article 68 of the Constitution of Kuwait | Monarch | The Emir declares defensive war by decree. Offensive war is prohibited. | ||||
| scope=row | Mexico[43] | President | Article 89 § VIII of the Mexican Constitution | Congress | The President may declare war in the name of the United Mexican States after the correspondent law is enacted by the Congress of the Union. | ||||
| scope=row | Netherlands[44] | States General | Article 96 of the Constitution of the Netherlands | States General | |||||
| scope=row | Qatar | Monarch | Article 71 of the Constitution of Qatar | Monarch | Defensive war shall be declared by an Emiri decree and aggressive war is prohibited. | ||||
| scope=row | Russia | President | Article 71 and 86 of the Constitution of Russia[45] [46] | President | Per Article 71: "The jurisdiction of the Russian Federation includes [...] foreign policy and international relations of the Russian Federation, international treaties and agreements of the Russian Federation, issues of war and peace;" Per Article 86:a "The President of the Russian Federation shall: [...] govern the foreign policy of the Russian Federation;" | ||||
| scope=row | Saudi Arabia | Monarch | Article 61 of the Basic Law of Saudi Arabia | Monarch | |||||
| scope=row | Spain | Monarch | Article 63 of the Spanish constitution of 1978 | Parliament | The King, with prior authorization by the Parliament, has the power to declare war and make peace. | ||||
| scope=row | Sweden[47] | Cabinet | 2010:1408 15 kap. 14 § entitled "Krigsförklaring" | Parliament | The Swedish cabinet (regeringen) may not declare Sweden to be at war without the parliament's (riksdagen) consent unless Sweden is attacked first. | ||||
| scope=row | Turkey | Parliament | Article 87 and 92 of the Constitution of Turkey | Parliament | The President may declare Turkey to be at war without the parliament's consent if the parliament is adjourned or in recess and Turkey is attacked first. | ||||
| scope=row | United Kingdom | Monarch[48] [49] | None | Monarch[50] | See: Declarations of war by Great Britain and the United Kingdom. | ||||
| scope=row | United States[51] [52] | Congress | Article 1, Section 8 of the Constitution of the United States | Congress | See: Declaration of war by the United States. |