This is a timeline of declarations of war during World War II.
A declaration of war is a formal act by which one nation goes to war against another. The declaration is usually the act of delivering a performative speech or the presentation of a signed document by an authorized party of a national government in order to create a state of war between two or more sovereign states. The official international protocol for declaring war was defined in The Hague Peace Conference of 1907 (or Hague II). For the diplomatic maneuvering behind these events, which led to hostilities between nations during World War II, see Diplomatic history of World War II.
List of war declarations
Indicated in the table are the dates (during the preliminaries to, or during the course of, World War II), from which a de facto state of war existed between nations. The table shows the "Initiator Nation(s)" and the nation at which the aggression was aimed, or "Targeted Nation(s)". Events listed include those in which there were simple diplomatic breaking of relations that did not involve hostilities, as well as those involving overt declarations or acts of aggression. In rare cases, war between two nations occurred twice, with an intermittent period of peace. The list here does not include peace treaties or periods of any armistice.
| Key to type (fourth column): | |
| A | Attack without prior, formal declaration of war; |
| C | Declaration and/or attack without standard, formal procedure, sometimes preceded by a casus belli thus fait accompli; |
| U | State of war arrived at through use of ultimatum; |
| W | Formal declaration of war made. |
| Date | Initiator nation(s) | Targeted nation(s) | Type | Notes/comments | Document/event |
|---|---|---|---|---|---|
| 1939-09-01 | Germany | Poland | A | German attack began at 4:44 a.m., Berlin and Warsaw time.[better source needed] Germany claimed that the attack was defensive, citing the Gleiwitz incident, which was actually a false flag attack. | Invasion |
| 1939-09-01 | Slovakia | Poland | A | Invasion | |
| 1939-09-03 | United Kingdom Australia New Zealand India Southern Rhodesia Tonga Transjordan | Germany | U | At 11:15 a.m. London time, British PM, Neville Chamberlain publicly delivered his Ultimatum Speech. As the Statute of Westminster 1931 was not yet ratified by the parliaments of Australia and New Zealand, the British declaration of war on Germany also applied to those dominions. Tonga was not a British dominion, instead, as part of the British Commonwealth (a protected state of the UK and the British Empire) declared war separately, alongside Britain (since it administers their foreign affairs). | British declaration |
| 1939-09-03 | France Morocco Tunisia | Germany | U | The French ultimatum to Germany expired a few hours after the British ultimatum, at 17:00. | French declaration |
| 1939-09-04 | Nepal | Germany | W | Declaration | |
| 1939-09-06 | South Africa | Germany | W | Declaration | |
| 1939-09-10 | Bahrain Canada Oman | Germany | W | Canada's declaration several days after that of the United Kingdom is seen as a watershed moment in Canadian home rule and sovereignty. As for Bahrain, given its status as a protected state of the United Kingdom, it was technically at war as of Britain's declaration, this is an acknowledgement of the declaration of war by Britain (due to coercion by an advisor), Oman, under British influence, is coerced to participate in the war effort. | Bahrainian declaration Canadian declaration Muscatian and Omanian declaration |
| 1939-09-17 | Soviet Union | Poland | A | Invasion | |
| 1939-11-09 | Kuwait | Germany | W | Declaration | |
| 1939-11-30 | Soviet Union | Finland | A | Invasion | |
| 1940-04-09 | Germany | Denmark Norway | A | Invasion of Denmark Invasion of Norway | |
| 1940-04-12 | United Kingdom | Faroe Islands | A | Invasion | |
| 1940-05-10 | Germany | Belgium Luxembourg Netherlands | A/W | Date of the German offensive in the West, W from Belgium, Luxemburg and the Netherlands. | Belgium Luxembourg Netherlands |
| 1940-05-10 | United Kingdom | Iceland | A | Invasion | |
| 1940-06-10 | Italy | France United Kingdom | W | Declaration | |
| 1940-06-10 | Canada | Italy | W | Declaration | |
| 1940-06-11 | South Africa Australia New Zealand France | Italy | W | South African declaration Australian declaration New Zealand's declaration French declaration | |
| 1940-07-03 | United Kingdom | Vichy France | A | Vichy France cuts off diplomatic relations with the United Kingdom on 8 July 1940. | Attack |
| 1940-09-09 | Italy | Egypt | A | Egypt never formally declared war on Italy. | Invasion |
| 1940-09-22 | Japan | Vichy France | A | Japanese troops occupy French Indochina. | Invasion |
| 1940-09-23 | Free France United Kingdom Australia | Vichy France | A | Invasion | |
| 1940-10-?? | Thailand | Vichy France | A | Franco-Thai War | |
| 1940-10-28 | Italy | Greece | U | Italy invades Greece. | Invasion |
| 1940-10-27 | Free France | Vichy France | A | Free French Equatorial Africa invades Vichy French Gabon. | Invasion |
| 1940-11-23 | Belgium (in-exile) | Italy | W | Declaration | |
| 1941-02-05 | Free France | Italy | A | Invasion | |
| 1941-04-06 | Germany | Greece | W | Invasion | |
| 1941-04-06 | Germany Italy | Yugoslavia | A | Invasion | |
| 1941-04-07 | Yugoslavia | Hungary | A | After the German invasion, bombing of Hungarian locations. | Invasion |
| 1941-04-14 | Germany | Egypt | A | Egypt did not formally declare war until 1945. | Invasion |
| 1941-05-02 | United Kingdom | Iraq | A | Invasion | |
| 1941-06-08 | Free France | Germany | A | [citation needed] | Invasion |
| 1941-06-22 | Germany Italy | Soviet Union | W | A timed declaration of war was given by Germany at the time of the attack. | Invasion |
| 1941-06-22/24 | Romania | Soviet Union | A | On June 22, Romanian leader Ion Antonescu declared a "holy war" to reclaim ancestral lands and against Bolshevism in an appeal to the nation. The Romanian army began limited military operations. On June 24, Romania officially declared war on the Soviet Union. | Declaration |
| 1941-06-22 | Tuva | Germany | W | Tuva was a client state of the Soviet Union. Part of the USSR from 1944. | Declaration |
| 1941-06-24 | Bulgaria | Greece Yugoslavia | A | Bulgaria declares war on Greece and Yugoslavia. | Declaration |
| 1941-06-25 | Finland | Soviet Union | W | After the bombing of several Finnish locations, Finland recognized a state of war with the Soviet Union; third war between these nations. | Continuation War |
| 1941-06-27 | Hungary | Soviet Union | C | After the bombing of several Hungarian locations, the Hungarian military concluded a Soviet attack, the Government had decided the two countries were already belligerent, without the consent of the Parliament, in absence of the Regent. | Invasion |
| 1941-08-25 | Soviet Union United Kingdom Australia | Iran | A | Invasion | |
| 1941-12-05 | United Kingdom India | Finland Romania Hungary | W | Declaration | |
| 1941-12-06 | Finland Romania | United Kingdom | W | Declaration | |
| 1941-12-07 | United Kingdom | Hungary | W | UK declaration of war from 1941-12-05 entered into force on 1941-12-07 1 minute after midnight. | Declaration |
| 1941-12-07 | Japan | United States United Kingdom Thailand | A | A formal message breaking off diplomatic talks was sent before but arrived after the attacks began, but this was not a declaration of war. See Attack on Pearl Harbor § Japanese declaration of war. | Declaration published after:
|
| 1941-12-07 | Canada Australia New Zealand | Finland Romania Hungary | W | Declaration | |
| 1941-12-07 | Panama Yugoslavia (in-exile) | Japan | W | Declaration | |
| 1941-12-08 | United Kingdom United States Canada Australia Costa Rica Dominican Republic El Salvador Free France Greece (in-exile) Haiti Honduras Netherlands (in-exile) New Zealand Nicaragua Philippines Tonga | Japan | W | After the attack on Pearl Harbor, many countries declared a formal state of war on Japan. | British declaration United States declaration Canadian declaration Australian declaration Costa Rican declaration Dominican Republic's declaration Salvadoran declaration Haitian declaration Honduran declaration Dutch declaration New Zealand's declaration Nicaraguan declaration Philippine declaration Tongan declaration |
| 1941-12-08 | South Africa | Japan Finland Romania Hungary | W | Declaration | |
| 1941-12-08 | Mongolia | Germany | W[citation needed] | Declaration | |
| 1941-12-08 | Manchukuo | United States | W | Declaration | |
| 1941-12-08 | Japan | British Malaya | A | Invasion of Malaya Attack on Singapore | |
| 1941-12-09 | Cuba Guatemala | Japan | W | Cuban declaration Guatemalan declaration | |
| 1941-12-09 | China | Germany Italy Japan | W | China and Japan had been at undeclared war since 1937. | Second Sino-Japanese war Declaration |
| 1941-12-10 | Korea (government in exile) | Japan | W | Many Korean armies such as the Korean Liberation Army had already been fighting Japan in the Second Sino-Japanese war, although a formal declaration was not made until the attack on Pearl Harbor. | Declaration |
| 1941-12-11 | Germany Italy | United States | W | German declaration Italian declaration | |
| 1941-12-11 | United States Cuba Costa Rica Dominican Republic Guatemala Nicaragua | Germany Italy | W | United States declaration of war on Germany (1941) United States declaration of war on Italy | |
| 1941-12-11 | Netherlands (in-exile) | Italy | W | Declaration | |
| 1941-12-11 | Poland (in-exile) | Japan | W | Japan rejected the declaration of war. Prime Minister Hideki Tōjō's answer was: "We don't accept the Polish declaration of war. The Poles, fighting for their freedom, declared war under the British pressure"[citation needed]. | Declaration |
| 1941-12-12 | Romania Bulgaria Slovakia | United States United Kingdom | W | Romanian declaration Bulgarian declaration | |
| 1941-12-12 | Haiti El Salvador Panama | Germany Italy | W | Declaration | |
| 1941-12-12 | Australia Netherlands | Portugal | A | Portugal maintained neutrality throughout World War II. | Invasion |
| 1941-12-13 | United Kingdom New Zealand South Africa | Bulgaria | W | British declaration New Zealand's declaration South African declaration | |
| 1941-12-13 | Honduras | Germany Italy | W | Declaration | |
| 1941-12-13 | Italy | Cuba Guatemala | W | Declaration | |
| 1941-12-14 | Independent State of Croatia | United States United Kingdom | W | Declaration | |
| 1941-12-15 | Hungary | United States | C | The Prime Minister informed the U.S. ambassador without approval of the Parliament and the Regent, but initially denied it would mean "war" in fact, however two days later he declared it means the two countries became belligerent. As the ambassador refused to accept the verbal form of this act, the next day the Prime Minister in written reinforced it. | Declaration |
| 1941-12-16 | Czechoslovakia (in-exile) | Germany Italy Finland Romania Hungary Japan Bulgaria Independent State of Croatia Slovakia | W | Czechoslovakia declares war on all countries at war with the United States of America, Great Britain and the Union of Soviet Socialist Republics. | Declaration |
| 1941-12-16 | Japan | Sarawak North Borneo Brunei | A | Invasion | |
| 1941-12-17 | Albania | United States | W | Declaration | |
| 1941-12-19 | Nicaragua | Romania Hungary Bulgaria | W | Declaration | |
| 1941-12-19 | Romania | Nicaragua | W | Out of the Axis countries only Romania reciprocated, declaring war on Nicaragua on the same day. | Declaration |
| 1941-12-20 | Belgium (in-exile) | Japan | W | Declaration | |
| 1941-12-24 | Haiti | Romania Hungary Bulgaria | W | Declaration | |
| 1941-12-24 | Romania | Haiti | W | Out of the Axis countries only Romania reciprocated, declaring war on Haiti on the same day. | Declaration |
| 1941-12-25 | Greece (in-exile) | Japan | W | Declaration | |
| 1942-01-01 | United Nations | Axis powers | W | Declared during Arcadia Conference. | Declaration |
| 1942-01-06 | Australia | Bulgaria | W | Declaration | |
| 1942-01-25 | Thailand | United Kingdom United States | A | Declaration | |
| 1942-01-25 | United Kingdom New Zealand South Africa | Thailand | W | British declaration New Zealand's declaration South African declaration | |
| 1942-02-19 | Japan | Portugal | A | Portugal maintained neutrality throughout World War II. | Invasion |
| 1942-03-02 | Australia | Thailand | W | Declaration | |
| 1942-05-05 | South Africa Netherlands (in-exile) Poland | Vichy France | A | Invasion | |
| 1942-05-05 | United Kingdom Northern Rhodesia Southern Rhodesia South Africa Tanganyika Belgian Congo | Vichy France Japan | A | Invasion | |
| 1942-05-22 | Mexico | Germany Italy Japan | W | Declaration | |
| 1942-06-05 | United States | Hungary Romania Bulgaria | W | Declaration of War on Hungary Declaration of War on Romania Declaration of war on Bulgaria | |
| 1942-06-13 | Iroquois Confederacy | Germany Italy Japan | W | Having never made peace with Germany from the First World War, Haudenosaunee became the only Native American state to officially declare war on the Axis powers separately from the United States (other Native American nations issued declarations or declared war de facto alongside the United States as their tribal citizens enlisted in the Armed Forces). | |
| 1942-08-22 | Brazil | Germany Italy | W | Declaration | |
| 1942-11-08 | United States Canada | Vichy France | A | Invasion | |
| 1942-11-10 | Germany Italy | Vichy France | A | Invasion | |
| 1942-11-12 | Germany | Tunisia | A | German invasion via airlifting several divisions in reaction to Operation Torch, swiftly occupying Tunis and the eastern part of the country, and capturing the western portions after French Tunisian resistance before the allies reached the Tunisian border. In the resulting Tunisian campaign, the Allies finally defeated the Axis forces in Africa. | Invasion |
| 1942-12-14 | Ethiopia | Germany Italy Japan | W | On 3 October 1935, Italy invaded Ethiopia without a formal declaration of war. In response to the Italian invasion, Ethiopia declared war on Italy. Most of Ethiopia was occupied by Italy in 1936, however parts of Ethiopia remained under the control of the Ethiopian Patriots Movement, which begun its guerrilla war against the occupying Italian forces the day Addis Ababa fell in May 1936. In May 1941, Addis Ababa was liberated by the Gideon Force, restoring sovereignty to Ethiopia. | Second Italo-Ethiopian War Declaration |
| 1943-01-09 | Reorganized National Government of China | United States United Kingdom | W | Declaration | |
| 1943-01-17 | Iraq | Germany Italy Japan | W | Declaration | |
| 1943-04-07 | Bolivia | Axis powers | W | Bolivia officially joined the Allies on 7 April 1943. Shortly after war was declared, the President, Enrique Peñaranda, was overthrown in a coup. Bolivian mines supplied needed tin to the Allies, but no troops or warplanes were sent overseas. Bolivians remained confident their geographic isolation would protect them from the war. | Declaration |
| 1943-08-01 | State of Burma | United States United Kingdom | W | Declaration | |
| 1943-09-08 | Germany | Italy Albania | A | After Italy's capitulation to the Allied powers, Germany swiftly invaded both Italy and Italian-controlled territories (such as Albania, an Italian satellite state) to preempt a possible Allied intervention. | Operation Achse German occupation of Albania |
| 1943-09-09 | Iran | Germany | W | Declaration | |
| 1943-10-13 | Italy | Germany | W | Italy had changed sides after the fall of Mussolini. The Declaration of War was given by Pietro Badoglio to the German ambassador in Madrid. | Declaration |
| 1943-11-26 | Colombia | Germany | W | See Colombia during World War II. | Declaration |
| 1944-01-17 | Free France | Italian Social Republic | A | Invasion | |
| 1944-01-27 | Liberia | Germany Japan | W | Declaration | |
| 1944-06-06 | France | Germany | A | Invasion | |
| 1944-07-25 | France | Japan | A | Invasion | |
| 1944-08-25 | Romania | Germany | W | Romania switched sides. | Declaration |
| 1944-09-05 | Soviet Union | Bulgaria | W | Declaration | |
| 1944-09-07 | Hungary | Romania | W | Declaration | |
| 1944-09-07 | Romania | Hungary | W | Declaration | |
| 1944-09-08 | Bulgaria | Germany | W [citation needed] | Bulgaria switched sides. | Declaration |
| 1944-09-15 | Germany | Finland | A | Lapland War | |
| 1944-09-23 | Second Philippine Republic | United States United Kingdom | W | Declaration | |
| 1944-12-28 | Hungary | Germany | W | The Provisional National Government, which had been established under Soviet protection in the city of Debrecen, declared war on Germany. The German-backed Arrow Cross regime was still at war with the Soviet Union and its troops were still in action. In January 1945, the Provisional National Government signed an armistice with the Allies, where it confirmed the declaration of war on Germany and obliged itself to form military forces loyal to the Allies. | Declaration |
| 1945-02-02 | Ecuador | Germany Japan | W | Declaration | |
| 1945-02-07 | Paraguay | Germany Japan | W | Declaration | |
| 1945-02-12 | Peru | Germany Japan | W | Declaration | |
| 1945-02-15 | Venezuela Uruguay | Germany Japan | W | Venezuelan declaration Uruguayan declaration | |
| 1945-02-23 | Turkey | Germany Japan | W | Declaration | |
| 1945-02-24 | Egypt | Germany Japan | W | Declaration | |
| 1945-02-26 | Syria Lebanon | Germany Japan | W | Declaration | |
| 1945-02-28 | Saudi Arabia | Germany | W | Declaration | |
| 1945-03-01 | Saudi Arabia | Japan | W | Declaration | |
| 1945-03-01 | Iran | Japan | W | Iran declared war on Japan retroactive to the previous day (Feb. 28, 1945). | Declaration |
| 1945-03-03 | Finland | Germany | W | Finland declared war on Germany retroactive to Sept. 15, 1944 following terms of 1944 Moscow Armistice. | Lapland War |
| 1945-03-07 | Romania | Japan | W | Declaration | |
| 1945-03-27 | Argentina | Germany Japan | W | Declaration | |
| 1945-04-11 | Chile | Japan | W | Chile cut off diplomatic relations with the Germany, Italy and Japan on 20 January 1943. | Declaration |
| 1945-06-07 | Brazil | Japan | W | Declaration | |
| 1945-07-09 | Norway (in-exile) | Japan | W | Norwegian government-in-exile announced that it had declared war on Japan on December 7, 1941. | Declaration |
| 1945-07-14 | Italy | Japan | W | Declaration | |
| 1945-08-08 | Soviet Union | Japan | W | Last outbreak of war of the Second World War. | Soviet–Japanese War |
| 1945-08-10 | Mongolia | Japan | W | W (de jure) A (de facto 1945-08-09) War declared 24 hours after crossing the border with Soviet troops. | Soviet Invasion of Manchuria Mongolia in World War II |
See also
- Diplomatic history of World War II
- Allies of World War II
- Axis powers: German Instrument of Surrender and Surrender of Japan
- Declarations of war during World War I
Bibliography
- Boog, Horst; Förster, Jürgen; Hoffmann, Joachim; Klink, Ernst; Müller, Rolf-Dieter; Ueberschär, Gerd R. (1998). Germany and the Second World War. Vol. 4. Oxford: Clarendon Press.
- Prange, Gordon William; Goldstein, Donald M.; Dillon, Katherine V. (1981). At Dawn We Slept: The Untold Story of Pearl Harbor. McGraw-Hill. ISBN 0-07-050669-8.
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