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Animated map of the European Theater of war during WW II

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 Outbreaks 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.[2]

Outbreaks of Wars between Nations during World War II
Table Legend: Concerning "Declaration of War: Type." A = Attack without prior, formal declaration of war; U = State of war arrived at through use of ultimatum;
W = Formal declaration of war made; D = Diplomatic breakdown leading to de facto state of war.
Date Initiator Nation(s) Targeted Nation(s) Declaration of War: Type Notes/Comments
1939-09-01 Germany Poland A [3][4] German attack began at 4:45 am[3][5]
1939-09-03 United Kingdom, France Germany U [3][4] At 11 O'clock (am) British PM, Neville Chamberlain publicly delivered his Ultimatum Speech.[4][6][7]
1939-09-03 Australia, New Zealand Germany W[3][4]
1939-09-06 South Africa Germany W[3][4]
1939-09-10 Canada Germany W[3][4]
1939-09-17 Soviet Union Poland A[3][4]
1939-11-30 Soviet Union Finland A[3][4] First war between these nations.
1940-04-09 Germany Denmark A[4] Norway W[4] A[3]
1940-05-10 Germany Belgium, Netherlands A/W[3][4] Date of the German offensive in the West, W from Belgium and the Netherlands.* [8]
1940-05-10 Germany Luxemburg A[4]
1940-06-10 Italy France, United Kingdom W[3][4]
1940-06-10 Canada Italy W[3]
1940-06-11 South Africa, Australia, New Zealand Italy W[3]
1940-06-11 France Italy [3]
1940-06-12 Egypt Italy D[4]
1940-07-04 Vichy France United Kingdom D[3][4] After the Fall of France (Operation Catapult), Germany occupied the North and the Atlantic coast, but for around two years southern France wasn't occupied and was known as Vichy France.
1940-10-28 Italy Greece U[4] Italy invades Greece
1941-04-06 Germany Greece W[3][4]
1941-04-06 Germany, Bulgaria Yugoslavia A[3][4]
1941-04-06 Italy, Hungary Yugoslavia A[4]
1941-04-23 Greece Bulgaria D[4]
1941-06-22 Germany, Italy, Romania, Bulgaria Soviet Union A[3][4] A timed-declaration of war was given by Germany at the time of the attack[9]
1941-06-25 Finland Soviet Union A[3][4] Finland recognized a state of war with the Soviet Union; second war between these nations.
1941-06-27 Hungary Soviet Union W[4]
1941-06-30 Vichy France Soviet Union D[4]
1941-12-06 United Kingdom Finland U[4]
1941-12-07 United Kingdom Romania, Hungary U[4]
1941-12-07 Empire of Japan United States A[3] W (Japanese point of view); A The "Western" (Attack on Pearl Harbor);
1941-12-07 Canada, Australia, New Zealand Japan, Finland, Romania, Hungary W[4]
1941-12-07 United Kingdom Romania, Finland and Hungary W[4]
1941-12-07 Panama Japan W[4]
1941-12-08 United States, United Kingdom, Australia, Costa Rica, Dominican Republic, El Salvador, Haiti, Honduras, The Netherlands, New Zealand and Nicaragua Japan W[4]
1941-12-08 Japan United Kingdom W[3][4]
1941-12-08 South Africa Japan W[4]
1941-12-08 China Germany, Italy, Japan W[4]
1941-12-09 Australia, New Zealand Japan W[4]
1941-12-11 Germany, Italy United States W[3][4]
1941-12-11 United States Germany, Italy W[3]
1941-12-12 Romania, Bulgaria, Czechoslovakia United States, United Kingdom W[4]
1941-12-13 United Kingdom, New Zealand, South Africa Bulgaria W[4]
1941-12-13 Hungary United States W[4]
1941-12-14 Croatia United States, United Kingdom W[4]
1941-12-16 Czechoslovak government-in-exile all countries at war with the United States, United Kingdom, or the Soviet Union W
1941-12-17 Albania United States W
1941-12-19 Nicaragua Bulgaria, Hungary and Romania W
1941-12-20 Belgium Japan W
1942-01-06 Australia Bulgaria W
1942-01-24 United States Denmark D
1942-01-25 United Kingdom, New Zealand, Union of South Africa Thailand W
1942-05-22 Mexico Germany, Italy, Japan W[4]
1942-08-22 Brazil Germany, Italy W
1942-11-09 Vichy France United States D[4]
1943-01-20 Chile Germany, Japan, Italy D
1943-04-02 Bolivia Axis members W
1943-09-09 Iran Germany W
1943-10-13 Italy Germany W[3] Italy had changed side after the fall of Mussolini. The Declaration of War was given by Pietro Badoglio to the German ambassador in Madrid.[3]
1944-08-25 Romania Germany W Romania switched sides
1944-09-05 Soviet Union Bulgaria W
1944-09-08 Bulgaria Germany D Bulgaria switched sides
1945-02-07 Argentina, Paraguay Germany, Japan W
1945-02-12 Peru Germany, Japan W
1945-02-15 Venezuela, Uruguay Germany, Japan W
1945-02-21 San Marino Germany W
1945-02-23 Turkey Germany, Japan W
1945-02-24 Egypt Germany, Japan W
1945-02-26 Syria Germany, Japan W
1945-04-01 Saudi Arabia Japan W
1945-04-03 Finland Germany W Finland switched sides
1945-04-11 Chile Japan W
1945-07-06 Brazil Japan W
1945-07-14 Italy Japan W
1945-08-08 Soviet Union Japan W[3] Last outbreak of war during the entire Second World War.

Literature[]

References[]

  1. On the Opening of Hostilities; 1907; Yale Law School Library; retrieved March 2014.
  2. Note: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 armistices.
  3. 3.00 3.01 3.02 3.03 3.04 3.05 3.06 3.07 3.08 3.09 3.10 3.11 3.12 3.13 3.14 3.15 3.16 3.17 3.18 3.19 3.20 3.21 3.22 3.23 3.24 3.25 "2194 Days of War"; (1977); Salmaggi, C. & Pallasvini, A.; ISBN 91-582-0426-1; per tables included. [Italian; American]
  4. 4.00 4.01 4.02 4.03 4.04 4.05 4.06 4.07 4.08 4.09 4.10 4.11 4.12 4.13 4.14 4.15 4.16 4.17 4.18 4.19 4.20 4.21 4.22 4.23 4.24 4.25 4.26 4.27 4.28 4.29 4.30 4.31 4.32 4.33 4.34 4.35 4.36 4.37 4.38 4.39 4.40 Timeline Data; World at War online; retrieved February 2014.
  5. On This Day
  6. 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..."
  7. 1939: Britain and France declare war on Germany, BBC
  8. Swedish Encyklopedia; "Bonniers Lexikon" (Vol. 1); (c.1960s); table in article by Andra Världskriget: The Second World War; Pp. 461-462.
  9. "The Rise and Fall of the Third Reich"; Shirer, William L
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