Declarations of war during World War II

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Animated map of the European theatre of war during WWII

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 an act of delivering a performative speech (not to be confused with a mere 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).[1] 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[]

Below is a table showing the outbreak of wars between nations which occurred during World War II. Indicated are the dates (during the immediate build-up to, or during the course of, World War II), from which a de facto state of war existed between nations. The table shows both 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 any physical attack, 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.

Outbreaks of war between nations during World War II
Date Initiator nation(s) Targeted nation(s) Type Notes/comments Document/event
1939-09-01 Nazi Germany Germany Poland U[2][3] German attack began at 4:44 a.m., Berlin and Warsaw time.[4][2][5] Invasion
1939-09-01  Slovak Republic Poland A Invasion
1939-09-03  United Kingdom
France
 Australia
 New Zealand
Tonga
Jordan Transjordan
Morocco
Tunisia
Nazi Germany Germany U[2][3] At 11:15 a.m. London time,[6] British PM, Neville Chamberlain publicly delivered his Ultimatum Speech.[3][a]>[7] 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, but declared war separately, alongside Britain.[8] The French ultimatum to Germany expired a few hours later at 17:00. United Kingdom declaration
French declaration
1939-09-04  Nepal Nazi Germany Germany W

1939-09-06 South Africa Nazi Germany Germany W[2][3]
1939-09-10 Bahrain
 Canada
Oman
Nazi Germany Germany W[2][3]

Declaration

1939-09-17  Soviet Union Poland A[2][3] Invasion
1939-11-09 Kuwait Kuwait Nazi Germany Germany W
1939-11-30  Soviet Union  Finland A[2][3] Second war between these nations (after Finnish invasion in 1918–1920). Invasion
1940-04-09 Nazi Germany Germany  Denmark
 Norway
A[2] Invasion of Denmark
Invasion of Norway
1940-04-12 United Kingdom  Faroe Islands A[3] Invasion
1940-05-10 Nazi Germany Germany  Belgium
 Netherlands
A/W[2][3] Date of the German offensive in the West, W from Belgium and the Netherlands.[9]

Belgium

Netherlands

1940-05-10 Nazi Germany Germany  Luxembourg A[3] Luxembourg
1940-05-10  United Kingdom Iceland Iceland A Invasion
1940-06-10 Italy France
 United Kingdom
W[2][3]
1940-06-10  Canada Italy W[2]
1940-06-11 South Africa
 Australia
 New Zealand
Italy W[2]

1940-06-11 France Italy W[2]
1940-06-25  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[3] Italy invades Greece Invasion
1940-11-23 Belgium (in-exile)  Italy W[10]
1941-02-05 Free France Italy A Invasion
1941-04-06 Nazi Germany Germany Greece W[2][3] Invasion
1941-04-06 Nazi Germany Germany Yugoslavia A[2][3] Invasion
1941-04-06 Italy Yugoslavia A[3] Invasion
1941-04-07 Yugoslavia Hungary A[11] After the German invasion, bombing of Hungarian locations Invasion
1941-04-14 Nazi Germany 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 Nazi Germany Germany A [citation needed] Invasion
1941-06-22 Nazi Germany Germany
Italy
Romania
 Soviet Union A[2][3] A timed-declaration of war was given by Germany at the time of the attack[12] Invasion
1941-06-22 Flag of the Tuvan People's Republic (1941-1943).svg
Tuva
Nazi Germany Germany W Tuva was a client state of the Soviet Union. Part of the USSR from 1944.
1941-06-25  Finland  Soviet Union W Finland recognized a state of war with the Soviet Union; third war between these nations. Continuation War
1941-06-27 Hungary  Soviet Union C[11] 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  Finland
Romania
Hungary
W[13]
1941-12-06  Finland
Romania
 United Kingdom W[3]
1941-12-07  United Kingdom Hungary W[14] UK declaration of war from 1941-12-05 entered into force on 1941-12-07 1 minute after midnight
1941-12-07  Japan  United States
 United Kingdom
 Thailand
W/A[2] W (Japanese point of view); A (British Empire and United States)

Declaration

Attack on Pearl Harbor

Invasion of Malaya

Attack on Singapore

Invasion of Hong Kong

Invasion of Thailand

1941-12-07  Canada
 Australia
 New Zealand
 Finland
Romania
Hungary
W[3] Declaration
1941-12-07  Canada
 Panama
 Japan W[3]
1941-12-08  United Kingdom
 United States
 Australia
 Costa Rica
 Dominican Republic
 El Salvador
 Guatemala
 Haiti
 Honduras
Netherlands (in-exile)
 New Zealand
 Nicaragua
 Philippines
Tonga[8]
 Japan W[3]

British declaration
United States declaration











1941-12-08 South Africa  Japan
 Finland
Romania
Hungary
W[3]
1941-12-08 Mongolia Nazi Germany Germany W[citation needed]

1941-12-08 Manchukuo  United States W[3]

1941-12-09  Australia
 New Zealand
Cuba
 Japan W[3]

1941-12-09  China Nazi Germany Germany
Italy
 Japan
W[3] China and Japan had been at undeclared war since 1937 Second Sino-Japanese war

1941-12-11 Nazi Germany Germany
Italy
 United States W[2][3]

German declaration

Italian declaration

1941-12-11  United States
Cuba
 Costa Rica
 Dominican Republic
 Guatemala
 Nicaragua
Nazi Germany Germany
Italy
W[3] Germany

Italy

1941-12-11 Netherlands (in-exile) Italy W[3] Declaration
1941-12-11 Poland (in-exile)  Japan W[2] Japan rejected 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].
1941-12-12 Romania
Bulgaria
 Slovak Republic
 United States
 United Kingdom
W[3]

1941-12-12  Haiti
 El Salvador
 Panama
Nazi Germany Germany
Italy
W[3] 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[3]

1941-12-13  Honduras Nazi Germany Germany
Italy
W[3] Declaration
1941-12-13 Italy Cuba
 Guatemala
W[3] Declaration
1941-12-14 Independent State of Croatia  United States
 United Kingdom
W[3]
1941-12-15 Hungary  United States C[15] 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.
1941-12-16 Czechoslovakia (in-exile) Nazi Germany Germany
Italy
 Finland
Romania
Hungary
Japan
Bulgaria
Independent State of Croatia
 Slovak Republic
W[3] Czechoslovakia declares war on all countries at war with the United States of America, Great Britain and the Union of Soviet Socialist Republics.
1941-12-17 Albania  United States W
1941-12-19  Nicaragua Romania
Hungary
Bulgaria
W[3] Declaration
1941-12-19 Romania  Nicaragua W[16] 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
1941-12-24  Haiti Romania
Hungary
Bulgaria
W[3] Declaration
1941-12-24 Romania  Haiti W[17] Out of the Axis countries only Romania reciprocated, declaring war on Haiti on the same day Declaration
1942-01-01 United Nations Axis Powers W Declared during Arcadia Conference Declaration
1942-01-06  Australia Bulgaria W
1942-01-25  Thailand  United Kingdom
 United States
A
1942-01-25  United Kingdom
 New Zealand
South Africa
 Thailand W

1942-02-19  Japan Portugal A Portugal maintained neutrality throughout World War II. Invasion
1941-03-02  Australia  Thailand W[3]

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 Nazi Germany Germany
Italy
 Japan
W[3] Declaration
1942-06-05  United States Hungary
Romania
Bulgaria
W[11] United States Declaration of War upon Hungary
United States Declaration of War upon Romania
United States declaration of war upon Bulgaria
1942-06-13 Iroquois Confederacy Nazi Germany Germany
Italy
 Japan
W Only Native American nation to have officially declared war on the Axis powers separately from the United States (other Native American nations declared war de facto alongside the United States with their tribal citizens enlisting in the Armed Forces). An Iroquois representative in full regalia announced on the steps of the U.S. Capitol by the following statement: "We represent the oldest, though smallest, democracy in the world today. It is the unanimous sentiment among Indian people that the atrocities of the Axis nations are violently repulsive to all sense of righteousness of our people, and that this merciless slaughter of mankind can no longer be tolerated. Now we do resolve that it is the sentiment of this council that the Six Nations of Indians declare that a state of war exists between our Confederacy of Six Nations on the one part and Germany, Italy, Japan and their allies against whom the United States has declared war, on the other part."[18]
1942-08-22 Brazil Nazi Germany Germany
Italy
W
1942-11-08 United States
Canada
Vichy France A Invasion
1942-11-10 Nazi Germany Germany
Italy
Vichy France A Invasion
1942-11-12 Nazi Germany 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 Nazi Germany 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

1943-01-09 Flag of the Republic of China-Nanjing (Peace, Anti-Communism, National Construction).svg Reorganized National Government of China  United States
 United Kingdom
W[3]
1943-01-17 Iraq Nazi Germany Germany
Italy
 Japan
W[3]
1943-01-20  Chile Nazi Germany Germany
Italy
W President Ríos officially suspended all trade and diplomatic relations with the Axis powers, and Chile officially joined the Allies as authorities began rooting out Nazi spies from Operation Bolivar. While only declaring war on Germany and Italy (although Chile would not declare war on Japan until 1945, it began imprisoning Japanese nationals in 1943), the American government and international press celebrated this day as Chile declaring war on the Axis.
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.
1943-08-01 Flag of the State of Burma (1943–1945).svg State of Burma  United States
 United Kingdom
W[3]
1943-09-08 Nazi Germany 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 Nazi Germany Germany W
1943-10-13 Italy Nazi Germany Germany W[2] Italy had changed sides after the fall of Mussolini. The Declaration of War was given by Pietro Badoglio to the German ambassador in Madrid.[2]
1943-11-26 Colombia Nazi Germany Germany W See Colombia during World War II
1944-01-17 Free France Italian Social Republic A Invasion
1944-01-27 Liberia Nazi Germany Germany
 Japan
W
1944-06-06
France
Nazi Germany Germany A Invasion
1944-07-25
France
 Japan A Invasion
1944-08-25 Romania Nazi Germany Germany W[3] Romania switched sides
1944-09-05  Soviet Union Bulgaria W
1944-09-07 Hungary Romania W[3]
1944-09-07 Romania Hungary W[3]
1944-09-08 Bulgaria Nazi Germany Germany W Bulgaria switched sides
1944-09-15 Nazi Germany Germany  Finland A Lapland War
1944-09-21  San Marino Nazi Germany Germany
Italian Social Republic Italian Social Republic
A Battle of San Marino
1944-09-23  Second Philippine Republic  United States
 United Kingdom
W[19]
1944-12-28  Hungary  Germany W[20] 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. As it had not switched sides of its own accord, Hungary was never recognized as having defected to the Allies. Hungarian declaration
1945-02-02  Ecuador Nazi Germany Germany
 Japan
W
1945-02-07  Paraguay Nazi Germany Germany
 Japan
W
1945-02-12  Peru Nazi Germany Germany
 Japan
W[3]
1945-02-15 Venezuela
 Uruguay
Nazi Germany Germany
 Japan
W

1945-02-23  Turkey Nazi Germany Germany
 Japan
W
1945-02-24 Egypt Nazi Germany Germany
 Japan
W
1945-02-26 Syria
 Lebanon
Nazi Germany Germany
 Japan
W
1945-02-28  Saudi Arabia Nazi Germany Germany W
1945-03-01  Saudi Arabia  Japan W[3]
1945-03-01 Iran  Japan W[3] Iran declares war on Japan retroactive to the previous day (Feb. 28, 1945)
1945-03-03  Finland Nazi Germany Germany W Finland declares war on Germany retroactive to Sept. 15, 1944 following terms of 1944 Moscow Armistice Lapland War
1945-03-07 Romania  Japan W[3]
1945-03-27  Argentina Nazi Germany Germany
 Japan
W

1945-04-11  Chile  Japan W
1945-06-07 Brazil  Japan W[3]
1945-07-09 Norway Norway (in-exile)  Japan W Norwegian government-in-exile announces that it had declared war on Japan on December 7, 1941 [21]
1945-07-14 Italy  Japan W
1945-08-08  Soviet Union  Japan W[2] Last outbreak of war during the entire Second World War. Soviet–Japanese War
1945-08-10 Mongolia  Japan W[22] 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

Gallery[]

See also[]

Notes[]

  1. ^ Included in the speech: "...This morning, the British Ambassador in Berlin handed the German Government a final note, stating that unless we heard from them by 11 O'clock that they were prepared at once to withdraw their troops from Poland a state of war would exist between us. I have to tell you now that no such undertaking has been received and that consequently this country is at war with Germany..."

References[]

  1. ^ On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.
  2. ^ Jump up to: a b c d e f g h i j k l m n o p q r s t u v "2194 Days of War"; (1977); Salmaggi, C. & Pallasvini, A.; ISBN 91-582-0426-1; per tables included. [Italian; American]
  3. ^ Jump up to: a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai aj ak al am an ao ap aq ar as at au av aw Doody, Richard, "Chronology of World War II Diplomacy 1939 - 1945", World at War, archived from the original on May 5, 2016, retrieved February 2014 Check date values in: |accessdate= (help)
  4. ^ "Germans invade Poland". History.com. Retrieved 1 Dec 2019.
  5. ^ "BBC ON THIS DAY | 1". news.bbc.co.uk.
  6. ^ Mann, Andrea. "September 3, 1939: Britain declares war on Germany after Hitler's troops invade Poland". BT.com. Retrieved 1 Dec 2019.
  7. ^ 1939: Britain and France declare war on Germany, BBC
  8. ^ Jump up to: a b "The United States Invasion of Tonga In 1942". Retrieved 23 July 2021.
  9. ^ Swedish Encyklopedia; "Bonniers Lexikon" (Vol. 1); (c.1960s); table in article by Andra Världskriget: The Second World War; Pp. 461-462.
  10. ^ Veranneman, Jean-Michel (30 September 2014). Belgium in WWII. ISBN 9781783376070.
  11. ^ Jump up to: a b c "Táblázat az egyes államok hadiállapotba kerüléséről". arcanum.hu. Arcanum Adatbázis Kft.
  12. ^ "The Rise and Fall of the Third Reich"; Shirer, William L
  13. ^ "BBC - WW2 People's War - Timeline". www.bbc.co.uk.
  14. ^ "Hadiállapot Magyarország és Nagy-Britannia között". arcanum.hu. Arcanum Adatbázis Kft.
  15. ^ Draveczki-Ury, Ádám (11 December 2011). "Hetven éve történt: hadüzenet az Egyesült Államoknak". honvedelem.hu. Honvédelmi Minisztérium.
  16. ^ Dr Erik Goldstein, Routledge, 2005, Wars and Peace Treaties: 1816 to 1991, p. 218
  17. ^ Dr Erik Goldstein, Routledge, 2005, Wars and Peace Treaties: 1816 to 1991, p. 217
  18. ^ Treuer, David (22 January 2019). The Heartbeat of Wounded Knee: Native America from 1890 to the Present. Riverhead Books.
  19. ^ "1. United States/Philippines (1898-1946)".
  20. ^ "Az új államiság kiépítése Magyarországon | Magyarok a II. világháborúban | Kézikönyvtár". www.arcanum.hu. Retrieved 2021-04-01.
  21. ^ "Norway Declares War on Japan". Canberra Times (Act : 1926 - 1995). 9 July 1945. p. 1.
  22. ^ Christopher P. Atwood (1999), "Sino-Soviet Diplomacy and the Second Partition of Mongolia, 1945–1946", Mongolia in the Twentieth Century: Landlocked Cosmopolitan, Bruce A. Elleman and Stephen Kotkin, eds. (Armonk, NY: M. E. Sharpe), 147.
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