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United States President Franklin D. Roosevelt signs a declaration of war against Nazi Germany on December 11, 1941.

A declaration of war is a formal act by which one nation goes to war against another. The declaration is a performative speech act (or the 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, 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 use of force in international conflicts, have made declarations of war largely obsolete in international relations.[1] In addition to this, non-state or terrorist organisations may claim to or be described as "declaring war" when engaging in violent acts.[2][3] These declarations may have no legal standing in themselves, but may still act as a call to arms for supporters of these organisations.


Theoretical perspectives

A definition of the three ways of thinking about a declaration of war was developed by Saikrishna Prakash.[4] He argues that a declaration of war can be seen from three perspectives:

  • Categorical theory, under which the power to declare war includes "the power to control all decisions to enter war". This means that the power to 'declare war' in effect rests with the ability to engage in combat.
  • Pragmatic theory, which states that the power to declare war can be made unnecessary by an act of war in itself.
  • Formalist theory, under which the power to declare war constitutes only a formal documentation of executive war-making decisions. This sits closest to traditional legal conceptions of what it is to declare a war.[5]

Types of declarations

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An alternative typology based upon the form of the declaration is formulated by Brien Hallett [6] according to 1) the degree to which the state and condition of war exists, 2) the degree of justification, 3) the degree of ceremony of the speech act, and 4) the degree of perfection of the speech act:

Degree of existence of the war
  • A conditional declaration of war declares war conditionally, threatening war if the grievances listed are not acknowledged and the preferred remedies demanded are not accepted.
  • An absolute declaration of war declares war absolutely due to the failure of negotiations over the grievances and remedies found in the conditional declaration. It ends absolutely the state and condition of peace, replacing it with the state and condition of war until such time as peace is restored.
Degree of justification of the war
  • A reasoned declaration of war justifies the resort to war by stating the grievances that have made peace intolerable and the remedies that will restore peace.
  • An unreasoned declaration of war does not justify the resort to war, or does so only minimally.
Degree of ceremony with which the speech act was made
  • A formal or solemn declaration of war is a declaration made by the constitutionally recognized nation following the appropriate laws, rites and rituals.
  • An informal or unsolemn declaration of war is a declaration made in an irregular manner either by a constitutionally unrecognized nation or by the constitutionally recognized nation using unlawful, inappropriate procedures.
Degree of perfection with which the speech act was made
  • A perfect declaration of war is a formal, solemn speech act made in accordance with the proper laws, rites, and rituals.
  • An imperfect declaration of war is an informal, unsolemn speech act not made in accordance with the proper laws, rites and rituals.


Adolf Hitler announcing a German declaration of war on the United States on 11 December 1941.

The practice of declaring war has a long history. The ancient Sumerian Epic of Gilgamesh gives an account of it,[7] as does the Old Testament.[8][9]

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 (UN) was established following that war in a renewed attempt to prevent international aggression through declarations of war.

Formal Declarations of War during World War II

3 September 1939 – United Kingdom, India, France, Australia and New Zealand declared war on Germany.
6 September 1939 – South Africa declared war on Germany.
10 September 1939 – Canada declared war on Germany.
24 April 1940 - Germany declared war on Norway[10]
10 May 1940 – Netherlands declared war on Germany.
10 June 1940 – Italy declared war on UK and France.
23 November 1940 – Belgian government in exile declared war on Italy.
25 June 1941 – Finland declared war on the Soviet Union.
27 June 1941 – Hungary declared war on the Soviet Union.
7 December 1941 – Empire of Japan declared war on the United States of America, United Kingdom, Australia, New Zealand, and South Africa.
7 December 1941 – United Kingdom, Canada, Australia and New Zealand declared war on Finland, Romania and Hungary.
7 December 1941 – Panama declared war on Japan.
8 December 1941 – The United States of America, United Kingdom, Canada, Australia, Costa Rica, The Dominican Republic, El Salvador, Haiti, Honduras, The Netherlands, New Zealand and Nicaragua declare war on Japan.
9 December 1941 – Republic of China declared war on Japan, Italy and Germany.
11 December 1941 – Germany and Italy declared war on the United States of America.
11 December 1941 – The United States of America declared war on Germany and Italy.
11 December 1941 – Polish government in exile declared war on Japan.
12 December 1941 – Bulgaria, Hungary, Romania and Slovakia declare war on the United States of America and United Kingdom.
13 December 1941 – United Kingdom, New Zealand and the Union of South Africa declare war on Bulgaria.
14 December 1941 – Croatia declared war on the United States of America and United Kingdom.
16 December 1941 – Czechoslovak government in exile declares war on all countries at war with the United States of America, United Kingdom and the Soviet Union.
17 December 1941 – Albania (under Italian occupation) declared war on the United States of America.
19 December 1941 – Nicaragua declared war on Bulgaria, Hungary and Romania.
20 December 1941 – Belgium declared war on Japan.
6 January 1942 – Australia declared war on Bulgaria.
25 January 1942 – United Kingdom, New Zealand and the Union of South Africa declare war on Thailand.
22 May 1942 – Mexico declared war on Germany, Italy and Japan.
22 August 1942 – Brazil declared war on Germany and Italy.
2 April 1943 – Bolivia declared war on all Axis members.
9 September 1943 – Iran declared war on Germany.
13 October 1943 – Italy (after switching sides) declared war on Germany.
24 October 1943 - Provisional Government of Free India declared war on Britain, and the United States of America.
25 August 1944 – Romania (after switching sides) declared war on Germany.
21 September 1944 – San Marino declared war on Germany.
22 September 1944 - The government of the Second Philippine Republic declares war on the United States and Great Britain. The declaration took effect the following day.
7 February 1945 – Argentina and Paraguay declared war on Germany and Japan.
12 February 1945 – Peru in state of belligerency with Germany and Japan.
15 February 1945 – Venezuela and Uruguay declare war on Germany and Japan.
23 February 1945 – Turkey declared war on Germany and Japan.
24 February 1945 – Egypt declared war on Germany and Japan.
26 February 1945 – Syria declared war on Germany and Japan.
1 March 1945 – Saudi Arabia declared war on Japan.
3 March 1945 – Finland (after switching sides) declared war on Germany.
11 April 1945 – Chile declared war on Japan.
6 July 1945 - Norway declared war on Japan[11]

After World War II

In 1989 Panama declared itself to be in a state of war with the United States.[13] On 13 May 1998, at the outbreak of the Ethiopian-Eritrean War, Ethiopia, in what Eritrean radio described as a "total war" policy, mobilized its forces for a full assault against Eritrea.[14] The Claims Commission found that this was in essence an affirmation of the existence of a state of war between belligerents, not a declaration of war, and that Ethiopia also notified the United Nations Security Council, as required under Article 51 of the UN Charter.[15]

In December 2005 the government of Chad declared that a state of war existed with Sudan, after Sudan hosted Chadian rebel groups that were behind fatal cross border raids.[16]

In 2008, after armed clashes broke out during the Djiboutian–Eritrean border conflict, Djibouti's President Guelleh, when asked if his country was at war with Eritrea, replied with "absolutely".[17]

On 11 April 2012, Sudan declared war on South Sudan after weeks of border clashes.[18]

Declared wars since 1945

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, United Kingdom, or Russia when faced with a hostile invasion and/or occupation.

This 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) Declaration Type Belligerents Ended References
Declaring party Opponent
Arab–Israeli War (1948–49)
Suez Crisis (1956)
Six-Day War (1967)
War of Attrition (1967-70)
Yom Kippur War (1973)
15 May 1948 declaration of war Kingdom of Egypt Egypt
Syria Syria
Kingdom of Iraq Iraq
 Israel Egypt: 26 March 1979
Jordan: 26 October 1994
Syria: still at war
Iraq: still at war
Lebanon: did not participate
Ogaden War 13 July 1977 declaration of war  Somalia Ethiopia Ethiopia 15 March 1978
Iran–Iraq War 22 September 1980 declaration of war Iraq Iraq  Iran 20 July 1988 [20]
Falklands War 11 May 1982 declaration of a war zone  Argentina  United Kingdom 20 June 1982 [21]
United States invasion of Panama 15 December 1989 existence of a state of war  Panama United States 31 January 1990 [22]
Eritrean–Ethiopian War 14 May 1998 existence of a state of war  Ethiopia  Eritrea 25 May 2000 [14]
Chadian Civil War (2005–10) 23 December 2005 declaration of war  Chad  Sudan 15 January 2010 [23]
Djiboutian–Eritrean border conflict 13 June 2008 existence of a state of war  Djibouti  Eritrea 6 June 2010 [17]
2008 South Ossetia war 9 August 2008 existence of a state of war  Georgia  Russia  16 August 2008 [24]
Heglig Crisis 11 April 2012 existence of a state of war  Sudan  South Sudan 26 May 2012 [25]

United Nations and war

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 war combatant itself after North Korea invaded South Korea on 25 June 1950 (see 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, U.S. President Harry S. Truman characterized these hostilities as not being a "war" but a "police action".[26]

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".[27][28]

Denigration of formal 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 touched off the Peloponnesian War.[29]

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."[30] 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."[31]

United States

In the United States, Congress, which makes the rules for the military, has the power under the constitution to "declare war". However neither the U.S. Constitution nor the law stipulate what format a declaration of war must take. War declarations have the force of law and are intended to be executed by the President as "commander in chief" of the armed forces. The last time Congress passed joint resolutions saying that a "state of war" existed was on 5 June 1942, when the U.S. declared war on Bulgaria, Hungary, and Romania.[32] Since then, the U.S. has used the term "authorization to use military force", as in the case against Iraq in 2003.

Sometimes decisions for military engagements were made by US presidents, without formal approval by Congress, based on UN Security Council resolutions that do not expressly declare the UN or its members to be at war. Part of the justification for the United States invasion of Panama was to capture Manuel Noriega (as a prisoner of war)[33] because he was declared a criminal rather than a belligerent.[citation needed]

In response to the attacks on 11 September 2001, the United States Congress passed the joint resolution Authorization for Use of Military Force Against Terrorists on 14 September 2001, which authorized the US President to fight the War on Terror.[34]

Agreed Procedure for the Opening of Hostilities

The Hague Convention (III) of 1907 called "Convention Relative to the Opening of Hostilities"[35] gives the international actions a country should perform when opening hostilities. The first two Articles say:

Article 1

The Contracting Powers recognize that hostilities between themselves must not commence without previous and explicit warning, in the form either of a reasoned declaration of war or of an ultimatum with conditional declaration of war.[36]

Article 2

The existence of a state of war must be notified to the neutral Powers without delay, and shall not take effect in regard to them until after the receipt of a notification, which may, however, be given by telegraph. Neutral Powers, nevertheless, cannot rely on the absence of notification if it is clearly established that they were in fact aware of the existence of a state of war.[37]

See also


  1. "Waging war: Parliament's role and responsibility" (PDF). House of Lords. 27 July 2006. Retrieved 21 April 2008. "Developments in international law since 1945, notably the United Nations (UN) Charter, including its prohibition on the threat or use of force in international relations, may well have made the declaration of war redundant as a formal international legal instrument (unlawful recourse to force does not sit happily with an idea of legal equality)." 
  2. "Basque raid 'declaration of war'". BBC News. 6 October 2007. Retrieved 21 April 2008. 
  3. Iraq: Sadr speaks on "open war" as al-Qaeda to launch new campaign Al-Bawaba News; 20-04-08; Accessed 21-04-08
  4. Unleashing the Dogs of War: What the Constitution Means by 'Declare War' Prakash, Saikrishna; 2007; Cornell Law Review, Vol. 93, October 2007; Subscription Required
  5. Scholarship on the "Declare War" Power 22-01-08; Accessed 21-04-08
  6. Brien Hallett, Declaring War, Cambridge University Press, 2012, ISBN 978-1-107-60857-3, pp 104-8
  7. Brien Hallett, The Lost Art of Declaring War, University of Illinois Press, 1998, ISBN 0-252-06726-6, pp. 65f.
  8. Deut. 20:10–12, Judg. 11:1–32.
  9. Brien Hallett, The Lost Art of Declaring War, University of Illinois Press, 1998, ISBN 0-252-06726-6, pp. 66f.
  14. 14.0 14.1 World: Africa Eritrea: 'Ethiopia pursues total war'. BBC News. 6 June 1998.
  15. Jus Ad Bellum Ethiopia's Claims 1–8(pdf) Eritrea Ethiopia Claims Commission Page 6. Paragraph 17 (A commentary on Eritrea Ethiopia Claims Commission findings)
  16. Hancock, Stephanie (23 December 2005). "Chad in 'state of war' with Sudan". BBC News. 
  17. 17.0 17.1 "France backing Djibouti in 'war'". BBC News. 13 June 2008. 
  19. Michael Oren (2003). Six Days of War. New York: Random House Ballantine Publishing Group. p. 5. ISBN 0-345-46192-4. 
  20. Robert Cowley (1996). "Iran-Iraq War". 
  21. "The Battle over the Falklands". BBC News. 1998. 
  22. Theodore Draper (29 March 1990). "Did Noriega delcare war?". New York Review of Books. 
  23. "Call to ease Chad-Sudan tension". BBC News. 25 December 2005. 
  24. Peter Walker (9 August 2008). "Georgia declares 'state of war' over South Ossetia". The Guardian. 
  25. Scott Baldauf (19 April 2012). "Sudan declares war on South Sudan". Christian Science Monitor. 
  26. "The President's News Conference". 1950-06-29. Retrieved 2007-07-03. 
  27. The United Nations Security Council – Its Role in the Iraq Crisis: A Brief Overview
  28. "UN Security Council Resolution 678 (1990)". UNHCR. Retrieved December 31, 2012. 
  29. Thucydides. History of the Peloponnesian War, Book II.
  30. Bynkershoek, Cornelius van. 1930. Quæstionum Juris Publici Liber Duo (1737). Trans. Tenney Frank. The Classics of International Law No. 14 (2). Publications of the Carnegie Endowment for International Peace. Oxford at the Clarendon Press. (I, ii, 8)
  31. Hall, William Edward. 1924. A Treatise on International Law. 8th ed. by A. Pearce Higgins. London: Humphrey Milford: Oxford University Press. (p. 444)
  32. "Joint Declarations by the (U.S.) Congress, June 5, 1942", Dept. of State Bulletin, 6 June 1942
  34. Text of Resolution,

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