This is a timeline of formal declarations of War during World War II .
World War II, also known as the Second World War, was a global war that lasted from 1939 to 1945. The vast majority of the world's countries—including all the great powers—eventually formed two opposing military alliances: the Allies and the Axis. A state of total war emerged, directly involving more than 100 million people from over 30 countries. The major participants threw their entire economic, industrial, and scientific capabilities behind the war effort, blurring the distinction between civilian and military resources. World War II was the deadliest conflict in human history, marked by 50 to 85 million fatalities, most of whom were civilians in the Soviet Union and China. It included massacres, the genocide of the Holocaust, strategic bombing, premeditated death from starvation and disease, and the only use of nuclear weapons in war.
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).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.
A declaration of war is a formal act by which one state goes to war against another. The declaration is a performative speech act by an authorized party of a national government, in order to create a state of war between two or more states.
War is a state of armed conflict between states, governments, societies and informal paramilitary groups, such as mercenaries, insurgents and militias. It is generally characterized by extreme violence, aggression, destruction, and mortality, using regular or irregular military forces. Warfare refers to the common activities and characteristics of types of war, or of wars in general. Total war is warfare that is not restricted to purely legitimate military targets, and can result in massive civilian or other non-combatant suffering and casualties.
The Hague Conventions of 1899 and 1907 are a series of international treaties and declarations negotiated at two international peace conferences at The Hague in the Netherlands. Along with the Geneva Conventions, the Hague Conventions were among the first formal statements of the laws of war and war crimes in the body of secular international law. A third conference was planned for 1914 and later rescheduled for 1915, but it did not take place due to the start of World War I.
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.
In law and government, de facto describes practices that exist in reality, even if not officially recognized by laws. It is commonly used to refer to what happens in practice, in contrast with de jure, which refers to things that happen according to law. Unofficial customs that are widely accepted are sometimes called de facto standards.
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.
|Date||Initiator nation(s)||Targeted nation(s)||Declaration of war: Type||Notes/comments||Document/event|
|1939-09-01||U||German attack began at 4:44 am||Invasion|
|1939-09-03||U||At 11 a.m., British PM, Neville Chamberlain publicly delivered his Ultimatum Speech.||Declaration|
|1939-11-30||A||First war between these nations.||Invasion|
|1940-04-09||A|| Invasion of Denmark |
Invasion of Norway
|1940-05-10||A/W||Date of the German offensive in the West, W from Belgium and the Netherlands.|
|1940-06-10||W||France and the UK|
|1940-06-25||A||Vichy France cuts off diplomatic relations with the United Kingdom on 8 July 1940.||Attack|
|1940-09-09||A||Egypt maintained neutrality until 1945.||Invasion|
|1940-10-28||U||Italy invades Greece||Invasion|
|1941-04-14||A||Egypt maintained neutrality until 1945.||Invasion|
|1941-06-22||A||A timed-declaration of war was given by Germany at the time of the attack||Invasion|
|W||Tuva was a client state of the Soviet Union. Part of the USSR from 1944.|
|1941-06-25||W||Finland recognized a state of war with the Soviet Union; second war between these nations.||Continuation War|
|1941-12-07||A||W (Japanese point of view); A (British Empire and United States)|
|1941-12-08||W|| United States declaration |
|1941-12-08||W||South African declaration|
|1941-12-08||W||China and Japan had been at war since 1937||Second Sino-Japanese war|
|1941-12-08||W[ citation needed ]|
|1941-12-11||W||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||A||Portugal maintained neutrality throughout World War II.|
|1942-01-01||United Nations||Axis Powers||W||Declared during Arcadia Conference||Declaration|
|1942-02-19||A||Portugal maintained neutrality throughout World War II.||Invasion|
|1942-12-14||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|
|1943-10-13||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|
|1944-08-25||W||Romania switched sides||Declaration|
|1944-09-08||W||Bulgaria switched sides||Declaration|
|1944-12-31||W||Hungary switched sides||Declaration|
|1945-04-03||W||Finland switched sides||Lapland War|
|1945-08-08||W||Last outbreak of war during the entire Second World War.||Declaration|
|1945-08-10||W||W (de jure) A (de facto 1945-08-09) War declared 24 hours after crossing the border with Soviet troops|
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The following events occurred in September 1939:
This is a timeline of formal declarations of War during World War I.