List of All War Declarations and Other Outbreaks of Hostilities

Regarding type of war outbreak (fourth column): A = Attack without a declaration of war, U = State of war emerged through ultimatum, WD = State of war emerged after formal declaration of war, D = Diplomatic breakdown leading to a state of war. In some cases a diplomatic breakdown later led to a state of war. Such cases are mentioned in the comments.

Date	Attacking Nation(s)	Attacked Nation(s)	Type	Comments
1939-09-01	Germany	Poland	A
1939-09-03	United Kingdom, France	Germany	U
1939-09-03	Australia, New Zealand	Germany	WD
1939-09-06	South Africa	Germany	WD
1939-09-10	Canada	Germany	WD
1939-09-17	Soviet Union	Poland	A
1939-11-30	Soviet Union	Finland	A	Diplomatic breakdown day before
1940-04-09	Germany	Denmark, Norway	A
1940-05-15	Germany	Belgium, Netherlands	WD	The German offensive in western Europe
1940-06-10	Italy	France, United Kingdom	WD	At a time when France already was about to fall
1940-06-10	Canada	Italy	WD
1940-06-11	South Africa, Australia, New Zealand	Italy	WD
1940-06-12	Egypt	Italy	D
1940-07-04	United Kingdom	France*	A	Vichy France Navy and colonies were attacked by UK, but no war was declared
1940-10-28	Italy	Greece	U
1941-04-06	Germany	Greece	WD
1941-04-06	Germany, Bulgaria	Yugoslavia	A
1941-04-06	Italy	Yugoslavia	WD
1941-04-10	Hungary	Yugoslavia	A
1941-04-23	Greece	Bulgaria	D
1941-06-22	Germany*, Italy, Romania	Soviet Union	WD	*The German declaration of war was given at the time of the attack
1941-06-24	Denmark	Soviet Union	D	Denmark was occupied by Germany
1941-06-25	Finland	Soviet Union	A	Second war between these nations.
1941-06-27	Hungary	Soviet Union	WD	Diplomatic breakdown 1941-06-24
1941-06-30	France	Soviet Union	D
1941-12-07	United Kingdom	Romania, Hungary, Finland	U	Diplomatic breakdowns 1941-02-11,1941-04-07 and 1941-08-01
1941-12-07	Japan	United States	A	WD came the day after.
1941-12-08	Japan	United Kingdom	WD
1941-12-08	Canada, South Africa	Japan	WD
1941-12-08	China	Germany*, Italy*, Japan	WD	*Diplomatic breakdown 1941-07-02
1941-12-09	Australia, New Zealand	Japan	WD
1941-12-11	Germany, Italy	United States	WD
1941-12-12	Romania	United States	WD
1941-12-13	Bulgaria	United Kingdom, United States	WD
1941-12-13	Hungary	United States	WD
1942-01-24	United States	Denmark	D
1942-05-28	Mexico	Germany, Italy, Japan	WD	Diplomatic breakdowns in all three cases 1941
1942-08-22	Brazil	Germany, Italy	WD	Diplomatic breakdowns 1942-01-20 and 1942-01-28
1942-11-09	France	United States	D
1943-01-20	Chile	Germany, Japan, Italy	D
1943-09-09	Iran	Germany	WD	Diplomatic breakdown in 1941
1943-10-13	Italy	Germany	WD	After the fall of Mussolini, Italy changed side
1944-01-10	Argentina	Germany, Japan	D
1944-06-30	United States	Finland	D
1944-08-04	Turkey	Germany	D	Turkey declared war on Germany on 23 Feb. 1945; a state of war against Germany existed from this date.
1944-08-23	Romania	Germany	WD	Like Italy, Romania also changed side.
1944-09-05	Soviet Union	Bulgaria	WD
1944-09-07	Bulgaria	Germany	D
1945-02-24	Egypt	Germany*, Japan	WD	*Diplomatic breakdown already 1939
1945	Argentina, Paraguay, Peru, Venezuela, Uruguay, Syria, and Saudi Arabia	Germany	WD	Needed a declaration to be eligible to join United Nations
1945-04-03	Finland	Germany	WD	Diplomatic breakdown in 1944, last outbreak in Europe.
1945-07-06	Brazil	Japan	WD
1945-07-17	Italy	Japan	WD
1945-08-08	Soviet Union	Japan	WD	Last outbreak of war during the Second World War.

 

William Orpen's painting The Signing of Peace in the Hall of Mirrors, Versailles, 28 June 1919, showing the signing of the peace treaty by the German Minister of Transport Dr Johannes Bell, opposite to the representatives of the winning powers.
Front Row: Dr Johannes Bell (Germany) signing with Herr Hermann Muller leaning over him.
Middle row (seated, left to right): General Tasker H Bliss, Col E M House, Mr Henry White, Mr Robert Lansing, President Woodrow Wilson (United States); M Georges Clemenceau (France); Mr D Lloyd George, Mr A Bonar Law, Mr Arthur J Balfour, Viscount Milner, Mr G N Barnes (Great Britain); The Marquis Saionzi (Japan).
Back row (left to right): M Eleutherios Venizelos (Greece); Dr Affonso Costa (Portugal); Lord Riddell (British Press); Sir George E Foster (Canada); M Nikola Pachitch (Serbia); M Stephen Pichon (France); Col Sir Maurice Hankey, Mr Edwin S Montagu (Great Britain); the Maharajah of Bikaner (India); Signor Vittorio Emanuele Orlando (Italy); M Paul Hymans (Belgium); General Louis Botha (South Africa); Mr W M Hughes (Australia).

Francisco Franco salutes Italian troops marching in his huge victory parade in Madrid, May 27, 1939. He celebrated his defeat of the Republicans in the Spanish Civil War under a triumphal arch decorated with his name and emblems. On July 17, 1936, Moroccan troops led by Gen. Francisco Franco rebelled against the Republican Government of Spain and thus began the Civil War that devastated the country. Germany and Italy sent troops, planes, and modern equipment to Franco, and Russia aided the Loyalists, who finally were forced to give up the struggle on March 28, 1939. The Spanish Civil War became a rehearsal for World War II, which burst upon the world approximately five months after the fighting ceased in Spain.

Defense Expenditure of the Major Belligerent Nations of World War II, 1930-1938.

German troops march into the Rhineland, 1936.

Adolf Hitler, age 35, on his release from Landesberg Prison, on December 20, 1924. Hitler had been convicted of treason for his role in an attempted coup in 1923 called the Beer Hall Putsch. This photograph was taken shortly after he finished dictating "Mein Kampf" to deputy Rudolf Hess. Eight years later, Hitler would be sworn in as Chancellor of Germany, in 1933.

Italian Fascist leader Benito Mussolini, center, hands on hips, with members of the fascist Party, in Rome, Italy, October 28, 1922, following their March on Rome. This march was an act of intimidation, where thousands of fascist blackshirts occupied strategic positions throughout much of Italy. Following the march, King Emanuelle III asked Mussolini to form a new government, clearing the way towards a dictatorship.

In Spain, loyalist soldiers teach target practice to women who are learning to defend the city of Barcelona against fascist rebel troops of general Francisco Franco during the Spanish Civil War, on June 2, 1937.

Three hundred fascist insurgents were killed in this explosion in Madrid, Spain, under the five-story Casa Blanca building, on March 19, 1938. Government loyalists tunneled 600 yards over a six-month period to lay the land mine that caused the explosion.

An insurgent fighter tosses a hand grenade over a barbed wire fence and into loyalist soldiers with machine guns blazing in Burgos, Spain, on Sept. 12, 1936.

German-made Stuka dive bombers, part of the Condor Legion, in flight above Spain on May 30, 1939, during the Spanish Civil War. The black-and-white "X" on the tail and wings is Saint Andrew's Cross, the insignia of Franco's Nationalist Air Force. The Condor Legion was composed of volunteers from the German Army and Air Force.

Scores of families are seen taking refuge underground on a Madrid subway platform, on December 9, 1936, as bombs are dropped by Franco's rebel aircraft overhead.

Aerial bombing of Barcelona in 1938 by Franco's Nationalist Air Force. The Spanish Civil War saw some of the earliest extensive use of aerial bombardment of civilian targets, and the development of new terror bombing techniques.

Following an aerial attack on Madrid from 16 rebel planes from Tetuan, Spanish Morocco, relatives of those trapped in ruined houses appeal for news of their loved ones, January 8, 1937. The faces of these women reflect the horror non-combatants are suffering in the civil struggle.

A Spanish rebel who surrendered is led to a summary court martial, as popular front volunteers and civil guards jeer, July 27, 1936, in Madrid, Spain.

A fascist machine gun squad, backed up by expert riflemen, hold a position along the rugged Huesca front in northern Spain, December 30, 1936.

Riette Kahn is shown at the wheel of an ambulance donated by the American movie industry to the Spanish government in Los Angeles, California, on Sept. 18, 1937. The Hollywood Caravan to Spain will first tour the U.S. to raise funds to "help the defenders of Spanish democracy" in the Spanish Civil War.