Declarations of war during World War II

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 the article entitled 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
DateInitiator nation(s)Targeted nation(s)TypeNotes/commentsDocument/event
1939-09-01 Germany PolandU[2][3]German attack began at 4:44 a.m., Berlin and Warsaw time.[4][2][5]Invasion
1939-09-01 Slovak Republic PolandAInvasion
1939-09-03 United Kingdom
France
 Australia
 New Zealand
Transjordan
Morocco
Tunisia
GermanyU[2][3]At 11:15 a.m. London time,[6] British PM, Neville Chamberlain publicly delivered his Ultimatum Speech.[3][7][8] 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 the those dominions. The French ultimatum to Germany expired a few hours later at 17:00. United Kingdom declaration
French declaration
1939-09-04 Nepal GermanyW

Declaration

1939-09-05 South Africa GermanyW[2][3]Declaration
1939-09-10 Bahrain
 Canada
Oman
GermanyW[2][3]Declaration

Declaration

Declaration

1939-09-17 Soviet Union PolandA[2][3]Invasion
1939-11-09 Kuwait GermanyWKuwaiti Declaration of War
1939-11-30 Soviet Union FinlandA[2][3]Second war between these nations (after Finnish invasion in 1918–1920).Invasion
1940-04-09 Germany Denmark
 Norway
A[2]Invasion of Denmark
Invasion of Norway
1940-04-12 United Kingdom Faroe IslandsA[3]Invasion
1940-05-10 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 Germany LuxembourgA[3]Luxembourg
1940-05-10  United Kingdom Iceland A Invasion
1940-06-10 Italy France
 United Kingdom
W[2][3]France and the UK
1940-06-10 Canada ItalyW[2]Declaration
1940-06-11 South Africa
 Australia
 New Zealand
ItalyW[2]

South Africa

Australia

New Zealand

1940-06-11 France ItalyW[2]Declaration
1940-06-25 United Kingdom Vichy FranceAVichy France cuts off diplomatic relations with the United Kingdom on 8 July 1940.Attack
1940-09-09 Italy EgyptAEgypt never formally declared war on Italy.Invasion
1940-09-22 Japan Vichy FranceAJapanese troops occupy French IndochinaInvasion
1940-09-23 Free France
 United Kingdom
 Australia
Vichy FranceAInvasion
1940-10-?? Thailand Vichy FranceAFranco-Thai War
1940-10-28 Italy GreeceU[3]Italy invades GreeceInvasion
1940-11-23 Belgium (in-exile) ItalyW[10]Declaration
1941-02-05 Free France ItalyAInvasion
1941-04-06 Germany GreeceW[2][3]Invasion
1941-04-06 Germany YugoslaviaA[2][3]Invasion
1941-04-06 Italy YugoslaviaA[3]Invasion
1941-04-07 Yugoslavia HungaryA[11]After the German invasion, bombing of Hungarian locationsInvasion
1941-04-14 Germany EgyptAEgypt did not formally declare war until 1945.Invasion
1941-05-02 United Kingdom IraqAInvasion
1941-06-08 Free France GermanyAInvasion
1941-06-22 Germany
Italy
Romania
 Soviet UnionA[2][3]A timed-declaration of war was given by Germany at the time of the attack[12]Invasion
1941-06-22
Tuva
GermanyWTuva was a client state of the Soviet Union. Part of the USSR from 1944.
1941-06-25 Finland Soviet UnionWFinland recognized a state of war with the Soviet Union; third war between these nations.Continuation War
1941-06-27 Hungary Soviet UnionC[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 RegentInvasion
1941-08-25 Soviet Union
 United Kingdom
 Australia
IranAInvasion
1941-12-05 United Kingdom Finland
Romania
Hungary
W[13]Declaration
1941-12-06 Finland
Romania
 United KingdomW[3]Declaration
1941-12-07 United Kingdom HungaryW[14]UK declaration of war from 1941-12-05 entered into force on 1941-12-07 1 minute after midnightDeclaration
1941-12-07 Japan United States
 United Kingdom
 Thailand
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
 JapanW[3]Declaration
1941-12-08 United Kingdom
 United States
 Australia
 Costa Rica
 Dominican Republic
 El Salvador
 Guatemala
 Haiti
 Honduras
Netherlands (in-exile)
 New Zealand
 Nicaragua
 Philippines
 JapanW[3]

British declaration
United States declaration
Australian declaration
Costa Rican declaration
Dominican Republic's declaration
Guatemalan declaration
Salvadoran declaration
Haitian declaration
Honduran declaration
Dutch declaration
New Zealand's declaration
Nicaraguan declaration
Philippine declaration

1941-12-08 South Africa Japan
 Finland
Romania
Hungary
W[3]South African declaration
1941-12-08 Mongolia GermanyW

Mongolian declaration

1941-12-08 Manchukuo United StatesW[3]

Manchukuo declaration

1941-12-09 Australia
 New Zealand
Cuba
 JapanW[3]

Australian declaration

New Zealand's declaration

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

Declaration

1941-12-11 Germany
Italy
 United StatesW[2][3]

German declaration

Italian declaration

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

Italy

1941-12-11 Netherlands (in-exile) ItalyW[3]Declaration
1941-12-11 Poland (in-exile) JapanW[2]Japan rejected declaration of War. Prime Minister Hideki Tōjō's answer was following: "We don't accept the Polish declaration of war. The Poles, fighting for their freedom, declared war under the British pressure".
1941-12-12 Romania
Bulgaria
 Slovak Republic
 United States
 United Kingdom
W[3]

Romanian declaration

Bulgarian declaration

1941-12-12 Haiti
 El Salvador
 Panama
Germany
Italy
W[3]Declaration
1941-12-12 Australia
 Netherlands
PortugalAPortugal maintained neutrality throughout World War II.

Invasion

1941-12-13 United Kingdom
 New Zealand
South Africa
BulgariaW[3]

British declaration

New Zealand's declaration

South African declaration

1941-12-13 Honduras 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]Declaration
1941-12-15 Hungary United StatesC[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.Declaration
1941-12-16 Czechoslovakia (in-exile) 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.Declaration
1941-12-17 Albania United StatesWDeclaration
1941-12-19 Nicaragua Romania
Hungary
Bulgaria
W[3]Declaration
1941-12-19 Romania NicaraguaW[16]Out of the Axis countries only Romania reciprocated, declaring war on Nicaragua on the same dayDeclaration
1941-12-20 Belgium (in-exile) JapanWDeclaration
1941-12-24 Haiti Romania
Hungary
Bulgaria
W[3]Declaration
1941-12-24 Romania HaitiW[17]Out of the Axis countries only Romania reciprocated, declaring war on Haiti on the same dayDeclaration
1942-01-01United NationsAxis PowersWDeclared during Arcadia ConferenceDeclaration
1942-01-06 Australia BulgariaWDeclaration
1942-01-16 Iraq Germany
Italy
 Japan
WDeclaration
1942-01-25 Thailand United Kingdom
 United States
ADeclaration
1942-01-25 United Kingdom
 New Zealand
South Africa
 ThailandW

British declaration

New Zealand's declaration

South African declaration

1942-02-12 Peru Germany
 Japan
WDeclaration
1942-02-19 Japan PortugalAPortugal maintained neutrality throughout World War II.Invasion
1942-05-05 South Africa
Netherlands (in-exile)
Poland
Vichy FranceAInvasion
1942-05-05 United Kingdom
Northern Rhodesia
Southern Rhodesia
South Africa
Tanganyika
Belgian Congo
Vichy France
 Japan
AInvasion
1942-05-22 Mexico 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 Germany
Italy
 Japan
WOnly 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]Declaration
1942-08-22 Brazil Germany
Italy
WDeclaration
1942-11-08 United States
Canada
Vichy FranceAInvasion
1942-11-10 Germany
Italy
Vichy FranceAInvasion
1942-11-12 Germany TunisiaAGerman invasion via airlifting serval 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
WOn 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

1943-01-20 Chile Germany
Italy
WPresident 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.Declaration
1943-04-02 BoliviaAxis powersWBolivia 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
1943-09-01 China Regime of Wang JingweiAllied PowersWDeclaration
1943-09-09 Iran GermanyWDeclaration
1943-10-13 Italy 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]Declaration
1943-11-26 Colombia GermanyWSee Colombia during World War IIDeclaration
1944-01-17 Free France Italian Social RepublicAInvasion
1944-01-27 Liberia Germany
 Japan
WDeclaration
1944-06-06
France
GermanyAInvasion
1944-07-25
France
 JapanAInvasion
1944-08-25 Romania Germany
Hungary
WRomania switched sidesDeclaration
1944-09-05 Soviet Union BulgariaWDeclaration
1944-09-08 Bulgaria GermanyWBulgaria switched sidesDeclaration
1944-09-15 Germany FinlandALapland War
1944-09-23 Second Philippine Republic United States
 United Kingdom
W[19]Philippine declaration
1945-02-02 Ecuador Germany
 Japan
WEcuadorian declaration
1945-02-07 Argentina
 Paraguay
Germany
 Japan
W

Argentinean declaration

Paraguayan declaration

1945-02-15 Venezuela
 Uruguay
Germany
 Japan
W

Venezuelan declaration

Uruguayan declaration

1945-02-21 San Marino GermanyWDeclaration
1945-02-23 Turkey Germany
 Japan
WDeclaration
1945-02-24 Egypt Germany
 Japan
WDeclaration
1945-02-26 Syria
 Lebanon
Germany
 Japan
WDeclaration
1945-02-28 Saudi Arabia GermanyWDeclaration
1945-03-03 Finland GermanyWFinland switched sidesLapland War
1945-04-01 Saudi Arabia JapanWDeclaration
1945-04-11 Chile JapanWDeclaration
1945-07-06 Brazil JapanWDeclaration
1945-07-09 Norway JapanWDeclaration[20]
1945-07-14 Italy JapanWDeclaration
1945-08-08 Soviet Union JapanW[2]Last outbreak of war during the entire Second World War.Declaration
1945-08-10 Mongolia JapanW[21]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

References

  1. On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.
  2. "2194 Days of War"; (1977); Salmaggi, C. & Pallasvini, A.; ISBN 91-582-0426-1; per tables included. [Italian; American]
  3. Timeline Data Archived May 5, 2016, at the Wayback Machine; World at War online; retrieved February 2014.
  4. "Germans invade Poland". History.com. Retrieved 1 Dec 2019.
  5. On This Day
  6. Mann, Andrea. "September 3, 1939: Britain declares war on Germany after Hitler's troops invade Poland". BT.com. Retrieved 1 Dec 2019.
  7. Note: 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..."
  8. 1939: Britain and France declare war on Germany, BBC
  9. Swedish Encyklopedia; "Bonniers Lexikon" (Vol. 1); (c.1960s); table in article by Andra Världskriget: The Second World War; Pp. 461-462.
  10. "Belgium in WWII".
  11. "Táblázat az egyes államok hadiállapotba kerüléséről". arcanum.hu. Arcanum Adatbázis Kft.
  12. "The Rise and Fall of the Third Reich"; Shirer, William L
  13. Declaration of War on Finland, Hungary and Romania
  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. https://trove.nla.gov.au/newspaper/article/2634950
  20. 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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