Declarations of war during World War II

Animated map of the European Theater of war during WWII

This is a timeline of formal 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

Table Legend: Concerning Declaration of War: A = Attack without prior, formal declaration of war; 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)	Declaration of war: Type	Notes/comments	Document/event
1939-09-01	Nazi Germany	Poland	U^[2]^[3]	German attack began at 4:44 am^[2]^[4]	Invasion
1939-09-01	Slovak Republic	Poland	A		Invasion
1939-09-03	United Kingdom France	Nazi Germany	U^[2]^[3]	At 11 a.m., British PM, Neville Chamberlain publicly delivered his Ultimatum Speech.^[3]^[5]^[6]	Declaration
1939-09-03	Australia New Zealand	Nazi Germany	W^[2]^[3]		Australia New Zealand
1939-09-04	Nepal	Nazi Germany	W		Declaration
1939-09-06	South Africa	Nazi Germany	W^[2]^[3]		Declaration
1939-09-10	Bahrain Canada Oman	Nazi Germany	W^[2]^[3]		Declaration Declaration Declaration
1939-09-17	Soviet Union	Poland	A^[2]^[3]		Invasion
1939-11-30	Soviet Union	Finland	A^[2]^[3]	First war between these nations.	Invasion
1940-04-09	Nazi 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	Belgium Netherlands	A/W^[2]^[3]	Date of the German offensive in the West, W from Belgium and the Netherlands.^[7]	Belgium Netherlands
1940-05-10	Nazi Germany	Luxembourg	A^[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	Italy	W^[2]		Declaration
1940-06-11	South Africa Australia New Zealand	Italy	W^[2]		South Africa Australia New Zealand
1940-06-11	France	Italy	W^[2]		Declaration
1940-06-16	Soviet Union	Lithuania	A		Occupation
1940-06-17	Soviet Union	Estonia Latvia	A		Occupation
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 maintained neutrality until 1945.	Invasion
1940-09-22	Japan	Vichy France	A		Invasion
1940-09-23	Free France 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
1941-02-05	Free France	Italy	A		Invasion
1941-04-06	Nazi Germany	Greece	W^[2]^[3]		Invasion
1941-04-06	Nazi Germany Bulgaria	Yugoslavia	A^[2]^[3]		Invasion
1941-04-06	Italy Hungary	Yugoslavia	A^[3]		Invasion
1941-04-14	Nazi Germany	Egypt	A	Egypt maintained neutrality until 1945.	Invasion
1941-05-02	United Kingdom	Iraq	A		Invasion
1941-06-08	Free France	Nazi Germany	A		Invasion
1941-06-22	Nazi Germany Italy Romania	Soviet Union	A^[2]^[3]	A timed-declaration of war was given by Germany at the time of the attack^[8]	Invasion
1941-06-22	Tuva	Nazi 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; second war between these nations.	Continuation War
1941-06-27	Hungary	Soviet Union	W^[3]		Invasion
1941-08-25	Soviet Union United Kingdom Australia	Iran	A		Invasion
1941-12-06	United Kingdom	Finland	U^[3]		Declaration
1941-12-07	United Kingdom	Romania Hungary	U^[3]		Declaration
1941-12-07	Japan	United States United Kingdom	A^[2]	W (Japanese point of view); A The "Western" (Attack on Pearl Harbor);	Declaration Attack on Pearl Harbor Invasion of Malaya Attack on Singapore Invasion of Hong Kong
1941-12-07	Canada Australia New Zealand	Japan Finland Romania Hungary	W^[3]		Canada Australia New Zealand
1941-12-07	United Kingdom	Romania Finland Hungary	W^[3]		Declaration
1941-12-07	Panama	Japan	W^[3]		Declaration
1941-12-08	United States United Kingdom Australia Philippines Costa Rica Dominican Republic El Salvador Guatemala Haiti Honduras Netherlands New Zealand Nicaragua	Japan	W^[3]		British declaration Australian declaration Cost Rican declaration Dominican Republic's declaration Salvadorian declaration Haitian declaration Honduran declaration Dutch declaration New Zealand's declaration Nicaraguan declaration Philippine declaration
1941-12-08	South Africa	Japan	W^[3]		South African declaration
1941-12-08	China	Italy Japan	W^[3]	China and Japan had been at war since 1937	Second Sino-Japanese war Declaration
1941-12-08	Mongolia	Nazi Germany	W		Mongolian declaration
1941-12-09	Australia New Zealand	Japan	W^[3]		Australian declaration New Zealand's declaration
1941-12-11	Nazi Germany Italy	United States	W^[2]^[3]		German declaration Italian declaration
1941-12-11	United States	Nazi Germany Italy	W^[2]		Germany Italy
1941-12-11	Poland (in-exile)	Japan	W^[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	United States United Kingdom	W^[3]		Romanian declaration Bulgarian 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]		British declaration New Zealand's declaration South African declaration
1941-12-13	Hungary	United States	W^[3]		Declaration
1941-12-14	Independent State of Croatia	United States United Kingdom	W^[3]		Declaration
1941-12-16	Czechoslovakia (In-exile)	Nazi Germany Italy Finland Romania Hungary Japan Bulgaria Independent State of Croatia^[9]	W		Declaration
1941-12-17	Albania	United States	W		Declaration
1941-12-19	Nicaragua	Bulgaria Hungary Romania	W		Declaration
1941-12-20	Belgium	Japan	W		Declaration
1942-01-01	United Nations	Axis Powers	W	Declared during Arcadia Conference	Declaration
1942-01-06	Australia	Bulgaria	W		Declaration
1942-01-16	Iraq	Nazi Germany Italy Japan	W		Declaration
1942-01-25	United Kingdom New Zealand South Africa	Thailand	W		British declaration New Zealand's declaration South African declaration
1942-01-19	Japan	Portugal	A	Portugal maintained neutrality throughout World War II.	Invasion
1942-02-12	Peru	Nazi Germany Japan	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	Nazi Germany Italy Japan	W^[3]		Declaration
1942-08-22	Brazil	Nazi Germany Italy	W		Declaration
1942-11-08	United States Canada	Vichy France	A		Invasion
1942-11-10	Nazi Germany Italy	Vichy France	A		Invasion
1942-12-14	Ethiopia	Nazi 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
1943-09-01	China Regime of Wang Jingwei	Allied Powers	W		Declaration
1943-04-02	Bolivia	Axis powers	W		Declaration
1943-09-09	Iran	Nazi Germany	W		Declaration
1943-10-13	Italy	Nazi 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	Nazi Germany	W		Declaration
1944-01-17	Free France	Italian Social Republic	A		Invasion
1944-01-27	Liberia	Nazi Germany Japan	W		Declaration
1944-06-06	France	Nazi Germany	A		Invasion
1944-07-25	France	Japan	A		Invasion
1944-08-25	Romania	Nazi Germany Hungary	W	Romania switched sides	Declaration
1944-09-05	Soviet Union	Bulgaria	W		Declaration
1944-09-08	Bulgaria	Nazi Germany	W	Bulgaria switched sides	Declaration
1944-09-15	Nazi Germany	Finland	A		Lapland War
1944-09-23	Second Philippine Republic	United States United Kingdom	W^[10]		Philippine declaration
1944-12-31	Hungary	Nazi Germany	W^[11]	Hungary switched sides	Declaration
1945-02-02	Ecuador	Nazi Germany Japan	W		Ecuadorian declaration
1945-02-07	Argentina Paraguay	Nazi Germany Japan	W		Argentinean declaration Paraguayan declaration
1945-02-15	Venezuela Uruguay	Nazi Germany Japan	W		Venezuelan declaration Uruguayan declaration
1945-02-21	San Marino	Nazi Germany	W		Declaration
1945-02-23	Turkey	Nazi Germany Japan	W		Declaration
1945-02-24	Egypt	Nazi Germany Japan	W		Declaration
1945-02-26	Syria Lebanon	Nazi Germany Japan	W		Declaration
1945-04-01	Saudi Arabia	Japan	W		Declaration
1945-04-03	Finland	Nazi Germany	W	Finland switched sides	Lapland War
1945-04-11	Chile	Japan	W		Declaration
1945-07-06	Brazil	Japan	W		Declaration
1945-07-09	Norway	Japan	W		Declaration^[12]
1945-07-14	Italy	Japan	W		Declaration
1945-08-08	Soviet Union	Japan	W^[2]	Last outbreak of war during the entire Second World War.	Declaration
1945-08-10	Mongolia	Japan	W^[13]	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

German ambassador, Hans-Adolf von Moltke, Polish leader Józef Piłsudski, German propaganda minister Joseph Goebbels and Józef Beck, Polish Foreign minister meeting in Warsaw on June 15, 1934, five months after signing the Polish-German Non-Aggression Pact.
British Prime Minister Neville Chamberlain, landing at Heston aerodrome on 30 September 1938 after his meeting with Hitler at Munich. In his hand he holds the peace agreement between Britain and Germany.
Common parade of German Wehrmacht and Soviet Red Army on September 23, 1939 in Brest, Eastern Poland at the end of the Poland Campaign. In the center is Major General Heinz Guderian; and on the right is Brigadier General Semyon Krivoshein.
Counsellor of state J.K. Paasikivi and his team arriving from Moscow for the first round of negotiations on 16 October 1939. From left, minister Aarno Yrjö-Koskinen, J.K. Paasikivi, chief of staff Johan Nykopp and colonel Aladár Paasonen.
German paratroopers taking the Greek island of Crete, May 1941.
Photograph from a Japanese plane of Battleship Row at the beginning of the surprise Attack on Pearl Harbor. The explosion in the center is a torpedo strike on the USS Oklahoma. Two attacking Japanese planes can be seen: one over the USS Neosho and one over the Naval Yard.

Literature about the war

Harman, Nicholas (1990). Dunkirk: the Necessary Myth. Jove. ISBN 978-0340517857.
German White Book. All World Wars.
Hitler, Adolph (2012). The Great Tragedy: Germany's Declaration of War against the United States of America. ISBN 978-1300127703.
Torrie, Julia S. (2010). "For Their Own Good": Civilian Evacuations in Germany and France, 1939–1945. Berghahn Books. ISBN 978-1845457259.

References

↑ On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 "2194 Days of War"; (1977); Salmaggi, C. & Pallasvini, A.; ISBN 91-582-0426-1; per tables included. [Italian; American]
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Timeline Data Archived May 5, 2016, at the Wayback Machine.; World at War online; retrieved February 2014.
↑ On This Day
↑ 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..."
↑ 1939: Britain and France declare war on Germany, BBC
↑ Swedish Encyklopedia; "Bonniers Lexikon" (Vol. 1); (c.1960s); table in article by Andra Världskriget: The Second World War; Pp. 461-462.
↑ "The Rise and Fall of the Third Reich"; Shirer, William L
↑ all countries at war with the United States, United Kingdom, or the Soviet Union
↑
↑ Hungary declares war on Germany
↑ https://trove.nla.gov.au/newspaper/article/2634950
↑ 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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[1] On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.

[Days-2] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 "2194 Days of War"; (1977); Salmaggi, C. & Pallasvini, A.; ISBN 91-582-0426-1; per tables included. [Italian; American]

[World-3] 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 Timeline Data Archived May 5, 2016, at the Wayback Machine.; World at War online; retrieved February 2014.

[4] On This Day

[5] 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..."

[6] 1939: Britain and France declare war on Germany, BBC

[7] Swedish Encyklopedia; "Bonniers Lexikon" (Vol. 1); (c.1960s); table in article by Andra Världskriget: The Second World War; Pp. 461-462.

[8] "The Rise and Fall of the Third Reich"; Shirer, William L

[9] untries at war with the United States, United Kingdom, or the Soviet Union

[10] ↑

[11] Hungary declares war on Germany

[12] ttps://trove.nla.gov.au/newspaper/article/2634950

[13] 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.