Declarations of war during World war II - wikipedia 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 ). 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. 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. Date Initiator Nation ( s ) Targeted Nation ( s ) Declaration of War : Type Notes / Comments Document / Event 1939 - 09 - 01 Nazi Germany Poland U German attack began at 4 : 44 am Invasion 1939 - 09 - 01 Slovak Republic Poland Invasion 1939 - 09 - 03 United Kingdom France Nazi Germany U At 11 a.m., British PM, Neville Chamberlain publicly delivered his Ultimatum Speech. Document Declaration 1939 - 09 - 03 Australia New Zealand Nazi Germany Australia New Zealand 1939 - 09 - 04 Nepal Nazi Germany Declaration 1939 - 09 - 06 South Africa Nazi Germany Declaration 1939 - 09 - 10 Bahrain Canada Oman Nazi Germany Declaration Declaration Declaration 1939 - 09 - 17 Soviet Union Poland Invasion 1939 - 11 - 30 Soviet Union Finland First war between these nations. Invasion 1940 - 04 - 09 Nazi Germany Denmark Norway Invasion of Denmark Invasion of Norway 1940 - 04 - 12 United Kingdom Faroe Islands Invasion 1940 - 05 - 10 Nazi Germany Belgium Netherlands A / W Date of the German offensive in the West, W from Belgium and the Netherlands. Belgium Netherlands 1940 - 05 - 10 Nazi Germany Luxembourg Luxembourg 1940 - 05 - 10 United Kingdom Iceland Invasion 1940 - 06 - 10 Italy France United Kingdom France and the UK 1940 - 06 - 10 Canada Italy Declaration 1940 - 06 - 11 South Africa Australia New Zealand Italy South Africa Australia New Zealand 1940 - 06 - 11 France Italy Declaration 1940 - 06 - 16 Soviet Union Lithuania Occupation 1940 - 06 - 17 Soviet Union Estonia Latvia Occupation 1940 - 06 - 25 United Kingdom Vichy France Vichy France cuts off diplomatic relations with the United Kingdom on 8 July 1940. Attack 1940 - 09 - 09 Italy Egypt Egypt maintained neutrality until 1945. Invasion 1940 - 09 - 22 Japan Vichy France Invasion 1940 - 09 - 23 Free France Australia Vichy France Invasion 1940 - 10 - ? ? Thailand Vichy France Franco - Thai War 1940 - 10 - 28 Italy Greece U Italy invades Greece Invasion 1941 - 02 - 05 Free France Italy Invasion 1941 - 04 - 06 Nazi Germany Greece Invasion 1941 - 04 - 06 Nazi Germany Bulgaria Yugoslavia Invasion 1941 - 04 - 06 Italy Hungary Yugoslavia Invasion 1941 - 04 - 14 Nazi Germany Egypt Egypt maintained neutrality until 1945. Invasion 1941 - 05 - 02 United Kingdom Iraq Invasion 1941 - 06 - 08 Free France Nazi Germany Invasion 1941 - 06 - 22 Nazi Germany Italy Romania Soviet Union A timed - declaration of war was given by Germany at the time of the attack Invasion 1941 - 06 - 22 Tuva Nazi Germany Tuva was a client state of the Soviet Union. Part of the USSR from 1944. 1941 - 06 - 25 Finland Soviet Union Finland recognized a state of war with the Soviet Union ; second war between these nations. Continuation War 1941 - 06 - 27 Hungary Soviet Union Invasion 1941 - 08 - 25 Soviet Union United Kingdom Australia Iran Invasion 1941 - 12 - 06 United Kingdom Finland U Declaration 1941 - 12 - 07 United Kingdom Romania Hungary U Declaration 1941 - 12 - 07 Japan United States United Kingdom 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 Canada Australia New Zealand 1941 - 12 - 07 United Kingdom Romania Finland Hungary Declaration 1941 - 12 - 07 Panama Japan Declaration 1941 - 12 - 08 United States United Kingdom Australia Philippines Costa Rica Dominican Republic El Salvador Guatemala Haiti Honduras Netherlands New Zealand Nicaragua Japan 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 South African declaration 1941 - 12 - 08 China Italy Japan China and Japan had been at war since 1937 Second Sino - Japanese war Declaration 1941 - 12 - 08 Mongolia Nazi Germany Mongolian declaration 1941 - 12 - 09 Australia New Zealand Japan Australian declaration New Zealand 's declaration 1941 - 12 - 11 Nazi Germany Italy United States German declaration Italian declaration 1941 - 12 - 11 United States Nazi Germany Italy Germany Italy 1941 - 12 - 11 Poland ( in - exile ) Japan Japan rejected declaration of War. Prime Minister Hideki Tōjō 's answer was following : `` We do n'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 Romanian declaration Bulgarian declaration 1941 - 12 - 12 Australia Netherlands Portugal Portugal maintained neutrality throughout World War II. Invasion 1941 - 12 - 13 United Kingdom New Zealand South Africa Bulgaria British declaration New Zealand 's declaration South African declaration 1941 - 12 - 13 Hungary United States Declaration 1941 - 12 - 14 Independent State of Croatia United States United Kingdom Declaration 1941 - 12 - 16 Czechoslovakia ( In - exile ) Nazi Germany Italy Finland Romania Hungary Japan Bulgaria Independent State of Croatia Declaration 1941 - 12 - 17 Albania United States Declaration 1941 - 12 - 19 Nicaragua Bulgaria Hungary Romania Declaration 1941 - 12 - 20 Belgium Japan Declaration 1942 - 01 - 01 United Nations Axis Powers Declared during Arcadia Conference Declaration 1942 - 01 - 06 Australia Bulgaria Declaration 1942 - 01 - 16 Iraq Nazi Germany Italy Japan Declaration 1942 - 01 - 25 United Kingdom New Zealand South Africa Thailand British declaration New Zealand 's declaration South African declaration 1942 - 01 - 19 Japan Portugal Portugal maintained neutrality throughout World War II. Invasion 1942 - 05 - 05 South Africa Netherlands ( in - exile ) Poland Vichy France Invasion 1942 - 05 - 05 United Kingdom Northern Rhodesia Southern Rhodesia South Africa Tanganyika Belgian Congo Vichy France Japan Invasion 1942 - 05 - 22 Mexico Nazi Germany Italy Japan Declaration 1942 - 08 - 22 Brazil Nazi Germany Italy Declaration 1942 - 11 - 08 United States Canada Vichy France Invasion 1942 - 11 - 10 Nazi Germany Italy Vichy France Invasion 1942 - 12 - 14 Ethiopia Nazi Germany Italy Japan 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 Declaration 1943 - 04 - 02 Bolivia Axis powers Declaration 1943 - 09 - 09 Iran Nazi Germany Declaration 1943 - 10 - 13 Italy Nazi Germany Italy had changed side after the fall of Mussolini. The Declaration of War was given by Pietro Badoglio to the German ambassador in Madrid. Declaration 1943 - 11 - 26 Colombia Nazi Germany Declaration 1944 - 01 - 17 Free France Italian Social Republic Invasion 1944 - 01 - 27 Liberia Nazi Germany Japan Declaration 1944 - 06 - 06 France Nazi Germany Invasion 1944 - 07 - 25 France Japan Invasion 1944 - 08 - 25 Romania Nazi Germany Hungary Romania switched sides Declaration 1944 - 09 - 05 Soviet Union Bulgaria Declaration 1944 - 09 - 08 Bulgaria Nazi Germany Bulgaria switched sides Declaration 1944 - 09 - 15 Nazi Germany Finland Lapland War 1944 - 09 - 23 Philippines United States United Kingdom Lapland War 1944 - 12 - 31 Hungary Nazi Germany Hungary switched sides Declaration 1945 - 02 - 02 Ecuador Nazi Germany Japan Ecuadorian declaration 1945 - 02 - 07 Argentina Paraguay Nazi Germany Japan Argentinean declaration Paraguayan declaration 1942 - 02 - 12 Peru Nazi Germany Japan Declaration 1945 - 02 - 15 Venezuela Uruguay Nazi Germany Japan Venezuelan declaration Uruguayan declaration 1945 - 02 - 21 San Marino Nazi Germany Declaration 1945 - 02 - 23 Turkey Nazi Germany Japan Declaration 1945 - 02 - 24 Egypt Nazi Germany Japan Declaration 1945 - 02 - 26 Syria Lebanon Nazi Germany Japan Declaration 1945 - 04 - 01 Saudi Arabia Japan Declaration 1945 - 04 - 03 Finland Nazi Germany Finland switched sides Lapland War 1945 - 04 - 11 Chile Japan Declaration 1945 - 07 - 06 Brazil Japan Declaration 1945 - 07 - 14 Italy Japan Declaration 1945 - 08 - 08 Soviet Union Japan Last outbreak of war during the entire Second World War. Declaration 1945 - 08 - 10 Mongolia Japan 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 Jump up ^ On the Opening of Hostilities ; 1907 ; Yale Law School Library ; retrieved March 2014. Jump up ^ 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. ^ Jump up to : `` 2194 Days of War '' ; ( 1977 ) ; Salmaggi, C. & Pallasvini, A. ; ISBN 91 - 582 - 0426 - 1 ; per tables included. ( Italian ; American ) ^ Jump up to : Timeline Data Archived May 5, 2016, at the Wayback Machine. ; World at War online ; retrieved February 2014. Jump up ^ On This Day Jump up ^ 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... '' Jump up ^ 1939 : Britain and France declare war on Germany, BBC Jump up ^ Swedish Encyklopedia ; `` Bonniers Lexikon '' ( Vol. 1 ) ; ( c. 1960s ) ; table in article by Andra Världskriget : The Second World War ; Pp. 461 - 462. Jump up ^ `` The Rise and Fall of the Third Reich '' ; Shirer, William L Jump up ^ all countries at war with the United States, United Kingdom, or the Soviet Union Jump up ^ ( 1 ) Jump up ^ Hungary declares war on Germany Jump up ^ 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. Retrieved from `` https://en.wikipedia.org/w/index.php?title=Declarations_of_war_during_World_War_II&oldid=853332002 '' Categories : Declarations of war Laws of war World War II Chronology of World War II Modern history timelines Hidden categories : Webarchive template wayback links All articles with unsourced statements Articles with unsourced statements from July 2017 Talk About Wikipedia Norsk Suomi Edit links This page was last edited on 4 August 2018, at 00 : 35 ( UTC ). Text is available under the Creative Commons Attribution - ShareAlike License ; additional terms may apply. By using this site, you agree to the Terms of Use and Privacy Policy. Wikipedia ® is a registered trademark of the Wikimedia Foundation, Inc., a non-profit organization. About Wikipedia

Question: when did germany declare war on belgium ww2
Answer: 1940-05-10