This timeline of events preceding World War II covers the events (mostly during the interwar period [1918–1939] after World War I) that affected or led to World War II.

Leaders of major participating countries

• 
  Benito Mussolini
  Italy
  1922–1943/45
• 
  Adolf Hitler
   Germany
  1933–1945
• 
  Hirohito
   Japan
  1926–1989
• 
  Chiang Kai-shek
   China
  1928–1975
• 
  Joseph Stalin
   Soviet Union
  1924–1953
• 
  Franklin D. Roosevelt
   United States
  1933–1945
• 
  Édouard Daladier
  France
  1938–1940

1895

October 8

Japanese agents assassinate Queen Min of Korea, removing a major obstacle to Japan's eventual conquest of Korea in the 1900s, ultimately facilitating Japan's invasion of Manchuria in 1931.^[1]

1905

September 5

The Treaty of Portsmouth formally ends the Russo-Japanese War, and concedes the Empire of Japan extraterritorial rights over the South Manchuria Railway Zone.^[2]

1910

August 22–29

Japan annexes Korea, further paving the way for the invasion of Manchuria in 1931.^[1]

1918

October 28–31

The Aster Revolution occurs establishing the First Hungarian Republic.

October 28

The German Revolution begins. It is sparked after the Imperial German Navy orders to send the High Seas Fleet to confront the British navy in a last stand attempt. Despite being planned that the mission would only be revealed when at sea, a rumor spreads that a combat mission is approaching and the sailors end up starting a mutiny as they feel it is a suicidal move. This mutiny ends up spreading to ports throughout the country.^[3]

November 11

The Armistice with Germany marks the end of World War I. German troops are given 72 hours to evacuate occupied territories^[4] and Allied troops subsequently move in and occupy the German Rhineland.^{[citation needed]}

November 13

The Hungarian–Romanian War begins.

December 27

Start of the Greater Poland Uprising against German rule.

1919

January 4–15

The Spartacist uprising takes place and is crushed by the German government.

January 18

Opening of the Paris Peace Conference to negotiate peace treaties between the belligerents of World War I.

January 31

Battle of George Square takes place in Glasgow, the British Army is called in by the city authorities to quell a riot during a strike for a 40 hour work week.

February

The Polish–Soviet War begins with border clashes between the two states.

February 13

Japan issues the Racial Equality Proposal during the Paris Peace Conference. The proposal would abolish racial discrimination but it founders on opposition from the United States, Australia and New Zealand.

March 2

Foundation of the Third International, or Comintern in Moscow. Comintern's stated aim is to create a global Soviet republic.

March 12

The Austrian Constituent National Assembly demands Austria's integration to Germany.^[5]

March 21

Proclamation of the communist Hungarian Soviet Republic.

May 15

The Turkish War of Independence begins as Greek troops land in Smyrna.

June 21

A majority of the German fleet is scuttled at Scapa Flow in Scotland. The ships had been interned there under the terms of the 1918 Armistice while negotiations were occurring over the ships fate. The Germans feared that either the British would seize the ships or Germany would reject the Versailles Treaty and resume the war effort altogether with the ships likely being used against Germany in this case.

June 28

Germany and the Allied powers sign the Treaty of Versailles after six months of negotiations. The German armed forces are limited in size to 100,000 personnel and Germany is ordered to pay large reparations for war damages. The United States signed the treaty but did not ratify it, later making a separate peace treaty with Germany.

July

An unknown corporal named Adolf Hitler infiltrates the German Workers' Party (the precursor of the Nazi Party) at the behest of the German Reichswehr.

August 1

Fall of the short-lived Hungarian Soviet Republic. The Hungarian People's Republic is reestablished.

August 3

The Hungarian–Romanian War ends.

August 8

The Hungarian People's Republic is dissolved.

September 10

German-Austria signs the Treaty of Saint-Germain. The peace treaty with the Allies regulates the borders of Austria, forbids union with Germany, and requires German-Austria to change its name to Austria. The United States did not ratify the treaty and later makes a separate peace treaty with Austria.

September 12

Gabriele D'Annunzio leads a force of Italian nationalist irregulars in the seizure of the disputed city of Fiume (Rijeka).

November 27

Bulgaria signs the Treaty of Neuilly-sur-Seine. The peace treaty gives Thrace back to Greece which was gained by them through the First Balkan War during 1913. While the Bulgarian army is reduced to 20,000 men and Bulgaria is ordered to pay war reparations.^[6]

1920

End of the western Allied intervention in the Russian Civil War with withdrawal of the last allied troops in Russia. (Japan continues its intervention until 1922.)

January 21

The Paris Peace Conference comes to an end with the inaugural General Assembly of the League of Nations. Although one of the victors of World War I, the United States never joins the League.

February 24

The National Socialist German Workers' Party (better known as the Nazi Party) is founded in Munich.^[7]

March

The failed right-wing Kapp Putsch takes place against the German government. The German military remains passive and the putsch is defeated by a general strike.

The German Ruhr Uprising, spurred by the general strike against the Kapp Putsch, is crushed by the German military

June 4

Hungary signs the Treaty of Trianon with the Allied powers. The treaty regulated the status of an independent Hungarian state and defined its borders. The United States did not ratify the treaty and later makes a separate peace treaty with Hungary.

August 10

The Ottoman Empire signs the Treaty of Sèvres with the Allied powers (except the US, which never declared war on Turkey). The treaty partitions the Ottoman Empire and the Turkish armed forces are reduced in size. Greece did not accept the borders as drawn up in the treaty and did not sign it. The Treaty of Sèvres was annulled in the course of the Turkish War of Independence and the parties signed and ratified the superseding Treaty of Lausanne in 1923.

October

Żeligowski's Mutiny, a Polish force led by General Lucjan Żeligowski, capture Vilnius, officially without support from the Polish state.

November 2

Franklin D. Roosevelt is defeated for the office of Vice President of the United States by Massachusetts Governor Calvin Coolidge.

November 15

The Free City of Danzig is established in accordance with the Treaty of Versailles, as a contentious compromise between the generally nationalist German majority in the city, and Poland's right to free and secure access to the sea.

December 24

Bloody Christmas: Italy occupies Fiume after five days of resistance from Gabriele D'Annunzio's legionnaires.

1921

Spring

Start of the Russian famine of 1921–1922 due to the combined effects of economic disturbance from the Russian Revolution, the Russian Civil War, and the government policy of war communism.

March 7–17

Red Army mutineers and Russian civilians seize the strategic city of Kronstadt in the Kronstadt Rebellion, demanding expanded civilian rights and an end to the Bolshevik monopoly on Soviet politics. After several days and several thousand casualties, the rebellion is crushed by Bolshevik forces from neighboring Petrograd.

March 18

The Polish–Soviet War ends with the Peace of Riga.

April 24

The Fiuman electorate approves the idea of a Free State of Fiume.

August 25

The U.S.–German Peace Treaty and the U.S.–Austrian Peace Treaty are signed, marking the formal end of the state of war between the two states and the United States instead of the Treaty of Versailles and the Treaty of Saint-Germain that were not ratified by the United States.

August 29

The U.S.–Hungarian Peace Treaty is signed, marking the formal end of the state of war between the two states instead of the Treaty of Trianon that was not ratified by the United States.

October 5

Foundation of the Sturmabteilung (SA), the paramilitary wing of the German Nazi Party.

November 9

Foundation of the Italian National Fascist Party by Benito Mussolini during the Third Fascist Congress in Rome.

1922

February 6

The Washington Naval Conference ends with the signing of the Washington Naval Treaty by the United Kingdom, the United States, Japan, France, and Italy. The signing parties agree to limit the size of their naval forces.

March

The first German officers travel to the Soviet Union for the purposes of military cooperation between Germany and the Soviet Union.

April 16

Germany and the Soviet Union sign the Treaty of Rapallo, re-establishing diplomatic relations, renouncing financial claims on each other, and pledging future economic cooperation.

October

The Russian Civil War (ongoing since 7 November 1917) ends in Bolshevik victory with the defeat of the last White forces in Siberia.

October 11

Armistice of Mudanya is signed in the Turkish War of Independence.

October 29

Fascist leader Benito Mussolini is appointed prime minister of Italy by king Victor Emmanuel III after the March on Rome.

November 1

The Grand National Assembly of Turkey abolishes the Ottoman Sultanate.

1923

January 11

France and Belgium occupy the Ruhr in an effort to compel Germany to step up its payments of war reparations.

January 26

The Nationalist Kuomintang party and the Chinese Communist Party form the First United Front to end warlordism in China.

June

In the great inflation of 1923, the value of the German mark is destroyed.

July 24

The Treaty of Lausanne, settling the boundaries of modern Turkey, is signed in Switzerland by Turkey and the Entente powers. It marks the end of the Turkish War of Independence and replaces the earlier Treaty of Sèvres

August 31

The Corfu incident: Italy bombards and occupies the Greek island of Corfu seeking to pressure Greece to pay reparations for the murder of an Italian general in Greece.

September 27

The Corfu incident ends; Italian troops withdraw after the Conference of Ambassadors rules in favor of Italian demands of reparations from Greece.

October 23–25

The Hamburg Uprising occurs.

October 29

Turkey officially becomes a Republic following the dissolution of the Ottoman Empire.

November 8

The Beer Hall Putsch takes place, in which Adolf Hitler unsuccessfully leads the Nazis in an attempt to overthrow the German government. It is crushed by police the next day.

1924

January 21

Leader of the Soviet Union Vladimir Lenin dies, and Joseph Stalin begins purging rivals to clear the way for his dictatorship.

February 1

The United Kingdom extends diplomatic recognition to the Soviet Union.

March 16

Italy annexes the Free State of Fiume.

April 1

Adolf Hitler is sentenced to 5 years in prison for his participation in the Beer Hall Putsch (he serves only 8 months).

April 6

Fascists win the 1924 Italian general election with a 2/3 majority.

June 10

Italian Fascists kidnap and kill socialist leader Giacomo Matteotti in Rome.

August 16

The Dawes Plan is accepted. It ends the Allied occupation of the Ruhr and sets a staggered plan for Germany's payment of war reparations.

August 18

France begins withdrawing its troops from the Ruhr in Germany.

1925

January 20

Signing of the Soviet–Japanese Basic Convention that normalizes relations between Japan and the Soviet Union.

April 4

Foundation of the paramilitary Nazi party organization the Schutzstaffel (SS). Originally intended as a personal bodyguard unit for party leader Adolf Hitler, the SS would grow in size and importance.

May 12

Retired Field Marshal Paul Von Hindenburg is elected President of Germany.

July 18

Hitler's autobiographical manifesto Mein Kampf is published.

December 1

The Locarno Treaties are signed in London (they are ratified September 14, 1926). The treaties settle the borders of western Europe and normalize relations between Germany and the Allied powers of western Europe.

1926

January 3

Theodoros Pangalos declares himself dictator of Greece. He would be elected president on April 4.

January 31

British and Belgian troops leave Cologne, Germany.

April 24

The Treaty of Berlin is signed by Germany and the Soviet Union, which declares neutrality if either country is attacked within the next five years.

September 8

Germany joins the League of Nations.

December 25

Emperor Taishō dies, and is succeeded by his son Hirohito as the Emperor of Japan.

1927

April 12

The Shanghai massacre of 5,000^[8]-10,000^[9] communists, perpetrated by the Kuomintang, marks the end of the First United Front and the beginning of the Chinese Civil War, which evolved into a proxy war between the Soviet Union and Nazi Germany until 1936.

May 20

Saudi Arabia and the United Kingdom sign the Treaty of Jeddah.

June 7

Peter Voikov, Soviet ambassador to Warsaw, is assassinated by a White movement activist.

November 12

Leon Trotsky is expelled from the Soviet Communist Party, leaving Joseph Stalin with undisputed control of the Soviet Union.

December 14

Iraq gains independence from the United Kingdom.

1928

May 3

The Jinan incident begins, a limited armed conflict between the Republic of China and Japan.^[10]

May 28

Foundation of the Chinese Red Army.

June 4

Huanggutun incident: Japanese agents assassinate the Chinese warlord Zhang Zuolin.^[11]

August 2

Italy and Ethiopia sign the Italo-Ethiopian Treaty, pledging cooperation and friendship.

August 27

The Kellogg–Briand Pact is signed in Paris by the major powers of the world. The treaty outlaws aggressive warfare.

October 1

The Soviet Union launches the first five-year plan, an economic effort to increase industrialization.

November 6

Herbert Hoover wins the 1928 US president election defeating Al Smith.

1929

February 9

Litvinov Protocol is signed in Moscow by the Soviet Union, Poland, Estonia, Romania, and Latvia. The Pact outlaws aggressive warfare along the lines of the Kellogg-Briand Pact.

February 11

Italy and the Holy See sign the Lateran Treaty, normalizing relations between the Vatican and Italy.

March 28

Japan withdraws troops from China, ending the Jinan incident.

April 3

Persia signs Litvinov's Pact.

June 7

The Lateran Treaty is ratified, making the Vatican City a sovereign state.

July 24

The Kellogg–Briand Pact goes into effect.

August 31

The Young Plan, which sets the total World War I reparations owed by Germany at US$26,350,000,000 to be paid over a period of 58½ years, is finalized. It replaces the earlier Dawes Plan.

October 29

The Great Depression begins with the Wall Street Crash.

1930

April 22

The United Kingdom, United States, France, Italy and Japan sign the London Naval Treaty regulating submarine warfare and limiting naval shipbuilding.

June 30

France withdraws its remaining troops from the Rhineland ending the occupation of the Rhineland.

September 14

German election results in the Nazis becoming the second-largest party in the Reichstag.

1931

May 19

Launching of the first Deutschland-class cruiser, Deutschland. The construction of the ship causes consternation abroad as it was expected that the restriction of 10,000 tons displacement for these ships would limit the German Navy to coastal defense vessels, not ships capable of warfare on the open sea.

September 18

Mukden Incident: the Japanese military stage a false flag bombing against a Japanese-controlled railroad in the Chinese region of Manchuria, blaming Chinese dissidents for the attack, an incident that is considered important in the lead up to World War II.^[12][13]

September 19

Using the Mukden Incident as a pretext, the Japanese invade Manchuria and create the Manchukuo puppet state.

1932

The Soviet famine of 1932–33, known in Ukraine as the Holodomor begins, caused in part by the collectivization of agriculture of the first five-year plan.

January 7

The Stimson Doctrine is proclaimed by United States Secretary of State Henry L. Stimson in response to Japan invading Manchuria. The Doctrine holds that the United States government will not recognize border changes that are made by force.

January 28

January 28 incident: using a flare-up of anti-Japanese violence as a pretext, the Japanese attack Shanghai, China. Fighting ends on March 6, and on May 5 a ceasefire agreement is signed wherein Shanghai is made a demilitarized zone.

February 27

Fighting between China and Japan in Manchuria ends with Japan in control of Manchuria.

March 1

Japan creates the puppet state Manchukuo out of occupied Manchuria.

April 10

Paul von Hindenburg is reelected President of Germany, defeating Adolf Hitler in a run-off.

May 4

The Soviet–Estonian Non-Aggression Pact is signed. It will enter into force on 18 August 1932 and will remain in force until 31 December 1945.

May 30

Chancellor of Germany Heinrich Brüning resigns. President Hindenburg asks Franz von Papen to form a new government.

July 25

Soviet–Polish Non-Aggression Pact is signed with it being initially effective for three years.

August 30

Hermann Göring is elected chairman of the German Reichstag.

November 4

Japan starts a counterinsurgency campaign in Manchukuo, known as the Pacification of Manchukuo.

November 8

Franklin D. Roosevelt defeats Herbert Hoover in the 1932 presidential election.

November 21

President Hindenburg begins talking to Hitler about forming a new government.

December 3

Hindenburg names Kurt von Schleicher Chancellor of Germany.

1933

January 1

Defense of the Great Wall: Japan attacks the fortified eastern end of the Great Wall of China in Rehe Province in Inner Mongolia.

January 30

Hitler is appointed Chancellor of Germany by President Hindenburg.^[14]

February 27

Germany's parliament building the Reichstag is set on fire.^[15]

February 28

Using the Reichstag fire as a pretext, the Reichstag Fire Decree is issued by President Paul von Hindenburg, nullifying many German civil liberties and paving the way for the Nazi seizure of power.^[15]

March 4

Franklin Delano Roosevelt is inaugurated as President of the United States. He launches the New Deal economic program, intended to counteract the effects of the Great Depression.

March 20

Germany's first concentration camp, Dachau, is completed.

March 23

The Reichstag passes the Enabling Act, making Adolf Hitler dictator of Germany.^[15]

March 24

Anti-Nazi boycott of 1933

March 27

Japan leaves the League of Nations over the League of Nations' Lytton Report that found that Manchuria belongs to China and that Manchukuo was not a truly independent state.

April 1

Germans are told to boycott Jewish shops and businesses.

April 26

The Gestapo secret police is established in Germany.

May 1

President Hindenburg and Chancellor Hitler appear before a crowd of 500,000 in Berlin as International Workers' Day is declared as "Day of National Labor" by the Nazi regime.^[16][17]

May 2

Hitler outlaws trade unions.

May 15

Official formation of the Luftwaffe, the German air force built in secret in violation of the Treaty of Versailles.

May 31

The Tanggu Truce is signed between China and Japan, setting the ceasefire conditions between the two states after the Japanese occupation of Manchuria. China accedes to all Japanese demands, creating a large demilitarized zone inside Chinese territory.

June 21

All non-Nazi parties are banned in Germany.

July 14

The Nazi party becomes the official party of Germany.

August 25

Haavara Agreement: The agreement was designed to help facilitate the emigration of German Jews to Palestine.

September 2

Italy and the USSR sign the Italo-Soviet Pact.^[18]

September 12

Leó Szilárd conceives the idea of the nuclear chain reaction.

October 19

Germany leaves the League of Nations over objections to the Conference for the Reduction and Limitation of Armaments.

November 16

The United States extends diplomatic recognition to the Soviet Union.

November 24

Homeless, alcoholic, and unemployed sent to Nazi concentration camps.

1934

January 26

Germany and Poland sign the 10 year German-Polish Non-Aggression Pact.^[19] From the German point of the view, the pact was intended to prevent Poland from intervening in an attempt to prevent the rearmament of Germany.^[20]

February 9

Balkan Pact, a military alliance is signed between Greece, Turkey, Romania and Yugoslavia.^[21] The intention of signing this treaty was to counteract plans being made by Italy to acquire new territories along with Bulgaria's intention to try and reclaim lost territories.^[22]

February 12–16

The Austrian Civil War is fought, ending with Austrofascist victory.

March 20

All German police forces come under the command of Heinrich Himmler.

May 5

Soviet–Polish Non-Aggression Pact is extented to December 31, 1945.

June 30

Night of the Long Knives in Germany. Potential rivals to Hitler within the Nazi Party, including SA leader Ernst Röhm and prominent anti-Nazi conservatives such as, former Chancellor Kurt von Schleicher, are killed by the SS and the Gestapo. Following this event, the SA continues to exist but loses almost all its influence and is effectively superseded by the SS.

July 20

The SS becomes an organization independent of the Nazi Party, reporting directly to Adolf Hitler.^[23]

July 25

Austrian Nazis assassinate Engelbert Dollfuss during the failed July Putsch against the Austrian government.

August 2

Upon the death of President Hindenburg, Hitler makes himself Führer of Germany, becoming Head of State as well as Chancellor.

August 8

Members of the Wehrmacht begin swearing a personal oath of loyalty to Hitler instead of to the German constitution.

September

The Soviet Union joins the League of Nations.

October 5

Left-wing parties in the Second Spanish Republic start the Revolution of 1934 against the right-wing government.

October 9

King Alexander I of Yugoslavia and French foreign minister Louis Barthou are assassinated in Marseilles^[24] Alexander's political murder further destabilized the Balkans. Barthou and Alexander were working for peace in Europe, particularly between Germany and the USSR, as they prepared both France and Yugoslavia for war.^[25] Prince Peter II takes Alexander's place but because he is a minor a regency council would take control.

October 16

Beginning of the Long March where the Chinese Red Army retreats to evade the pursuit of Kuomintang forces.

December 1

Sergei Kirov, head of the Leningrad Communist Party, is murdered by an unknown assailant, precipitating a wave of repression in the Soviet Union.

December 5

The Abyssinia Crisis begins with the Walwal incident, an armed clash between Italian and Ethiopian troops on the border of Ethiopia.

December 29

Japan renounces the Washington Naval Treaty and the London Naval Treaty.

1935

January 7

The League of Nations approves the results of the Saar plebiscite, which allows Saar to be incorporated into German borders.^[26]

June 18

The Anglo-German Naval Agreement is signed by Germany and the United Kingdom. The agreement allows Germany to build a fleet that's 35% the tonnage of the British fleet. In this way, the British hope to limit German naval rearmament.

August 31

The Neutrality Act of 1935 is passed in the United States imposing a general embargo on trading in arms and war materials with all parties in a war and it also declared that American citizens traveling on ships of warring nations traveled at their own risk.

September 15

The Reichstag passes the Nuremberg Laws, institutionalizing discrimination against Jews and providing the legal framework for the systematic persecution of Jews in Germany.

October 3

Italy invades Ethiopia, beginning the Second Italo–Abyssinian War. The League of Nations denounces Italy and calls for an oil embargo that fails.^[27]

November 14

Final British General election until 1945. Stanley Baldwin replaces Ramsay MacDonald as Prime Minister.

1936

January 20

George V, King of the United Kingdom dies.^[28] The Prince of Wales succeeds him as King Edward VIII.

February 6

Germany hosts the 1936 Winter Olympics in Garmisch-Partenkirchen, Bavaria.

February 26

The February 26 incident occurs in Japan where a group of 1,400 officers and soldiers of the Imperial Way faction stage a military coup which lasts until February 29 when the government suppresses the rebellion.^[29][30]

March 7

In violation of the Treaty of Versailles, Germany remilitarizes the Rhineland.

After the Rhineland move Hitler met separately with French journalist Bertrand de Jouvenal and British analyst Arnold J. Toynbee emphasizing his limited expansionist aim of building a greater German nation, and his desire for British understanding and cooperation.^[31]

King Edward VIII, over the head of the Baldwin Government, orders the military to stand down in relation to the move.

March 25

The Second London Naval Treaty is signed by the United Kingdom, United States, and France. Italy and Japan each declined to sign this treaty.

May 5

Italian troops march into the Ethiopian capital, Addis Ababa, marking the end of the Second Italo–Abyssinian War.

June 3

Luftwaffe Chief of Staff General Walther Wever loses his life in an air crash, ending any hope for the Luftwaffe to ever have a strategic bombing force similar to the Allies.

July 18

The Spanish coup of July 1936 by Nationalist forces marks the beginning of the Spanish Civil War. The coup initially begins in Spanish Morocco when a garrison of Spanish Foreign Legion soldiers rebel. This rebellion later spreads across the whole country.^[32]

August 1

Germany hosts the 1936 Summer Olympics in Berlin.

August 19

Commencement of the first Moscow show trials against Old Bolshevik Party leaders and top officials of the Soviet secret police.

October

The Great Purge commences in the Soviet Union with widespread repression of suspected opponents of the regime. The purge leads to the imprisonment and death of many military officers, weakening the Soviet Armed Forces ahead of World War II.

October 18

Göring is made head of the German Four Year Plan, an effort to make Germany self-sufficient through autarky and increase armaments.

November 3

Franklin D. Roosevelt wins reelection defeating Alf Landon.

November 14

Suiyuan campaign begins as Japanese-backed Mongolian troops attack the Chinese garrison at Hongort.

November 15

The aerial German Condor Legion goes into action for the first time in the Spanish Civil War in support of the Nationalist side.

November 25

The Anti-Comintern Pact is signed by Japan and Germany. The signing parties agree to go to war with the Soviet Union if one of the signatories is attacked by the Soviet Union.

December 1

Hitler makes it mandatory for all males between the ages 10-18 to join the Hitler Youth.

December 12

Kuomintang marshal Zhang Xueliang kidnaps Chinese leader Chiang Kai-Shek in order to compel the Kuomintang to make a truce with the Chinese Communist party for the purpose of fighting the invading Japanese.

Edward VIII is forced to abdicate due to his marriage to Wallis Simpson and is succeeded by Albert, Duke of York, who assumes the name King George VI

December 23

The first 3,000 men of the Italian expeditionary force (later named Corpo Truppe Volontarie) lands in Cadiz in support of the Nationalist side in the Spanish Civil War.

December 24

The Second United Front is formed between the Chinese Communist party and the Kuomintang, temporarily suspending the Chinese Civil War for the sake of fighting the Japanese.

1937

January 20

President Roosevelt begins his second term.

February 21

The Non-Intervention Committee of the League of Nations prohibits foreign intervention or involvement in the Spanish Civil War.

26 April

Bombing of Guernica by the German Condor Legion and the Italian Aviazione Legionaria at the behest of Franco's Nationalists in the Spanish Civil War. The bombing claims many civilian lives and draws widespread condemnation internationally.

May 7

The Condor Legion Fighter Group is deployed in Spain and begins to aid the Falangists.

May 28

Neville Chamberlain becomes Prime Minister of the United Kingdom.^[33]

June 21

Léon Blum's coalition government collapses.

July 7

The Marco Polo Bridge Incident occurs, beginning the Second Sino-Japanese War. Some scholars consider this to be the start of World War II.^[34][35] Japanese forces were doing military exercises near the Marco Polo Bridge;^[36] which begun on July 6^[37] which the Chinese objected to but let occur. The Chinese requested that locals be informed of exercises occurring at night which the Japanese promised but did not end up doing this.^[36] During that night Captain Shimizu reported one of his soldiers, Private Shimura as being missing as he was not present during a rollcall but later reappeared 20 minutes later. However Shimizu postponed reporting Shimizu's return by 4 hours for unknown reasons.^[38] The Japanese demanded they be granted access to search for the missing soldier in Chinese territory but the Chinese refused this request. Whether it was the Japanese or Chinese forces that fired first is unclear.^[39]

August 8

Japanese forces occupies the city of Beijing.

August 13

Second Sino-Japanese War: Battle of Shanghai commences.

October 5

President Roosevelt gives the Quarantine Speech outlining a move away from neutrality and towards "quarantining" all aggressors.^[40]

October 13

Germany notifies Belgium that its sovereignty will be guaranteed as long as Belgium refrains from taking part in military action against Germany.

November 5

Adolf Hitler holds a secret meeting in the Reich Chancellery and discusses the need for "lebensraum."

November 6

Italy joins the Anti-Comintern Pact.

November 26

Second Sino-Japanese War: Battle of Shanghai ends in Japanese victory as Chinese forces evacuate the city.

December 1

Second Sino-Japanese War: Battle of Nanjing commences as Japanese forces attack the city.

December 8

Japan established the puppet state of Mengjiang in the Inner Mongolia region of the Republic of China.^[41]

December 11

Italy leaves the League of Nations.

December 12

The USS Panay incident occurs, where Japanese aircraft attacked the American gunboat Panay which was carrying American evacuees and escorting four Standard Oil Barges. 3 people end up being killed in the attack while 11 are wounded; which leads to a diplomatic crisis between the US and Japan.^[42]

December 13

Second Sino-Japanese War: start of the Rape of Nanjing following Japanese victory in the Battle of Nanjing.

1938

January 26

The Allison incident occurs further straining relations between Japan and the United States.

March 6

Japanese troops reach the Yellow River in China.^[43]

March 13

The Anschluss: Germany annexes Austria.^[44]

March 24

Second Sino-Japanese War: Battle of Taierzhuang commences. The battle ends with Chinese victory on 7 April after intense house-to-house fighting inside the city of Taierzhuang.

Second Sino-Japanese War: Battle of Xuzhou begins, and ends in Japanese victory on May 1 as Chinese troops break out from the encircled city.

July 6–16

Évian Conference: The United States and the United Kingdom refuse to accept any more Jewish refugees.

July 29

The Soviet–Japanese border conflicts begin with the Battle of Lake Khasan.

August

Soviet Union wins the Battle of Lake Khasan against Japan.

September 27

U.S. President Roosevelt sends a letter to German Führer Adolf Hitler seeking peace.^[45]

September 30

The Munich Agreement is signed by Germany, France, the United Kingdom, and Italy. The agreement allows Germany to annex the Czechoslovak Sudetenland area in exchange for peace in an attempt to appease Hitler.^[46] Related: Polish–Czechoslovak border conflicts § Annexations by Poland in 1938.

October 5

Germany invalidates the passports of all its Jewish citizens who are reissued passports with the letter "J" stamped in red. This change was made after requests by Sweden and Switzerland who wanted a way of easily denying Jews entry into their countries.[1][2]

November 7

Polish-German Jew Herschel Grynszpan murders moderate German consular aide Ernst vom Rath in Paris.^[43][47]

November 9

vom Rath's death triggers Kristallnacht. Pogrom begins in Germany; thousands of Jewish shops and synagogues are smashed, looted, burned, and destroyed throughout the country.^[43]

1939

January 25

A uranium atom is split for the first time at Columbia University in the United States.^[48]

January 27

Hitler orders Plan Z, a 5-year naval expansion programme intended to provide for a huge German fleet capable of defeating the British Royal Navy by 1944. The Kriegsmarine is given the first priority on the allotment of German economic resources. This is the first and only time the Kriegsmarine is given the first priority in the history of the Third Reich.

March 14

The pro-German Slovak Republic is created.

March 15

Germany occupies and annexes Bohemia and Moravia-Silesia in violation of the Munich Agreement. The Czechs do not attempt to put up any organized resistance, having lost their main defensive line with the annexation of the Sudetenland.

Germany establishes the Protectorate of Bohemia and Moravia. The Second Czechoslovak Republic is dissolved.^[49]

Hungary invades the recently created Carpatho-Ukraine.^[50]

March 20

German Foreign Minister Joachim von Ribbentrop delivers an oral ultimatum to Lithuania, demanding that it cede the Klaipėda Region (German name Memel) to Germany.

March 21

Hitler demands the return of the Free City of Danzig to Germany.

March 23

German–Romanian Treaty for the Development of Economic Relations between the Two Countries is signed.

Germany annexes the Klaipėda Region.

Germany and Slovakia sign the Schutzzonenvertrag zwischen Deutschland und Slowakei [Treaty on the protective relationship between Germany and the Slovak State], creating the German Zone of Protection in Slovakia.

The Slovak–Hungarian War begins.

March 25

King Zog, the leader of Albania refuses Italy's ultimatum demanding the King hand over control of the country.^[51]

March 31

The United Kingdom and France offer a guarantee of Polish independence.^[52]

The Slovak–Hungarian War ends.

April 1

The Spanish Civil War ends in Nationalist victory. Spain becomes a dictatorship with Francisco Franco as the head of the new government serving until his death in 1975.^[53]

April 3

Hitler orders the German military to start planning for Fall Weiss, the codename for the attack on Poland, planned to be launched on August 25, 1939.

April 4

Hungary and Slovakia sign the Budapest Treaty, handing over a strip of eastern Slovak territory to Hungary.

April 7–12

Italy invades Albania with little in the way of military resistance in response to refusing the Italian ultimatum. Albania is later made part of Italy through a personal union of the Italian and Albanian crown.^[51]

April 14

U.S. President Roosevelt sends letter to German Chancellor Hitler and Italian Prime Minister Mussolini seeking peace.^[54]

April 18

The Soviet Union proposes a tripartite alliance with the United Kingdom and France. It is rejected.^[55]

April 28

In a speech before the Reichstag^{[citation needed]}, Hitler renounces the Anglo-German Naval Agreement.^[56]

April 29

Hitler renounces the German–Polish declaration of non-aggression.^[57]

May 11

Soviet–Japanese border conflicts: The Battle of Khalkhin Gol begins with Japan and Manchukuo against the Soviet Union and Mongolia. The battle ends in Soviet victory on September 16, influencing the Japanese not to seek further conflict with the Soviets, but to turn towards the Pacific holdings of the Euro-American powers instead.

May 17

Sweden, Norway, and Finland reject Germany's offer of non-aggression pacts.

May 22

The Pact of Steel, known formally as the "Pact of Friendship and Alliance between Germany and Italy", is signed by Fascist Italy and Nazi Germany. The Pact declares further cooperation between the two powers, but in a secret supplement the Pact is detailed as a military alliance.

May 31

Denmark and Germany sign a non-aggression pact which is later broken when Germany invades Denmark the following year.^[58]

June 7

The German–Estonian and the German–Latvian non-aggression pacts are concluded. They will remain in force for ten years.

June 14

The Tientsin incident occurs, in which the Japanese blockade the British concession in the North China Treaty Port of Tientsin, now called Tianjin.^[59]

July 10

Prime Minister Neville Chamberlain reaffirms support for Poland and makes it clear that Britain did not view Free City of Danzig as being an internal German-Polish affair and would intervene on behalf of Poland if hostilities broke out between the two countries.

August 2

The Einstein-Szilárd letter is sent to President Roosevelt. Written by Leó Szilárd and signed by Albert Einstein, it warned of the danger that Germany might develop atomic bombs. This letter prompted action by Roosevelt and eventually resulted in the Manhattan Project.

August 23

The Molotov–Ribbentrop Pact is signed between Nazi Germany and the Soviet Union, with secret provisions for the division of Eastern Europe – joint occupation of Poland and Soviet occupation of Estonia, Latvia and Lithuania, Finland and Bessarabia. This protocol removes the threat of Soviet intervention during the German invasion of Poland.^[60]

August 25

In response to a message from Mussolini that Italy will not honor the Pact of Steel if Germany attacks Poland, Hitler delays the launch of the invasion by five days to provide more time to secure British and French neutrality.^[60]

August 28

Tarnów train station bombing: A German agent named Antoni Guzy leaves a bomb inside two suitcases at the Tarnów train station in Poland that later explodes killing 24 people. It was one of several incidents done by Germany in Poland during the summer of 1939 to justify invading Poland.^[61]

August 30

Nazi Germany issues an ultimatum to Poland concerning the Polish Corridor and the Free City of Danzig.^[60]

Gleiwitz incident: Germany stages a false flag attack on the German radio station Sender Gleiwitz to manufacture a pretext for war with Poland.^[60]

September 1

Without response to its ultimatum, Germany invades Poland, start of World War II (the Soviet Union invades Poland on September 17).^[60]