Causes of World War II

Their ambitious and aggressive domestic and foreign policies reflected their ideologies of antisemitism, unification of all Germans, the acquisition of "living space" (Lebensraum) for agrarian settlers, the elimination of Bolshevism and the hegemony of an "Aryan"/"Nordic" master race over "subhumans" (Untermenschen) such as Jews and Slavs.

Other factors leading to the war included the aggression by Fascist Italy against Ethiopia, militarism in Imperial Japan against China, and Nationalists fighting against Republicans for control of Spain.

Britain and France rejected diplomatic efforts to form a military alliance with the Soviet Union, and Hitler instead offered Stalin a better deal in the Molotov–Ribbentrop Pact of August 1939.

[8] The German people largely viewed the treaty as placing the blame, or "war guilt", on Germany and Austria-Hungary and as punishing them for their "responsibility", rather than working out an agreement that would assure long-term peace.

The war in the east had ended with the defeat and the collapse of the Russian Empire, and German troops had occupied large parts of Eastern and Central Europe with varying degrees of control and established various client states such as a kingdom of Poland and the United Baltic Duchy.

In addition, the Treaty of Versailles dissolved the German general staff, and possession of navy ships, aircraft, poison gas, tanks and heavy artillery was also made illegal.

The old philosophy of "concert of nations", which grew out of the Congress of Vienna (1815), saw Europe as a shifting map of alliances among nation-states, which created a balance of power that was maintained by strong armies and secret agreements.

After the Treaty of Versailles, a unification between Germany and the newly formed German-Austria, a rump state of Austria-Hungary, was blocked by the Allies, despite the large majority of Austrians supporting the idea.

In the early 20th century, in the Russo-Japanese War, Japan had succeeded in pushing back the East Asian expansion of the Russian Empire in competition for Korea and Manchuria.

With oil reserves that would last only a year and a half during peacetime and much less during wartime, the ABCD line left Japan two choices: comply with the US-led demand to pull out of China or seize the oilfields in the East Indies from the Netherlands.

[28] In the late 1980s, the British historian Richard Overy was involved in a historical dispute with Timothy Mason that played out mostly over the pages of the Past and Present journal over the reasons for the outbreak of the war in 1939.

[29] The key aspects of the crisis were, according to Mason, a shaky economic recovery that was threatened by a rearmament program that overwhelmed the economy and in which the regime's nationalist bluster limited its options.

[29] Mason thought German foreign policy was driven by domestic political considerations, and the launch the war in 1939 was best understood as a "barbaric variant of social imperialism".

[34] Mason contended that when faced with the deep socio-economic crisis, the Nazi leadership had decided to embark upon a ruthless foreign policy of "smash and grab" to seize territory in Eastern Europe that could be pitilessly plundered to support the living standards in Germany.

[36] Mason's considered the decision to sign the Molotov–Ribbentrop Pact and to attack Poland despite the risk of a war against Britain and France to be the abandonment by Hitler of his foreign policy program outlined in Mein Kampf and to have been forced on him by his need to stop a collapsing German economy by seizing territory abroad to be plundered.

That aggressive strategy worked as Germany pulled out of the League of Nations (1933), rejected the Versailles Treaty, began to rearm with the Anglo-German Naval Agreement (1935), won back the Saar (1935), re-militarized the Rhineland (1936), formed an alliance ("axis") with Mussolini's Italy (1936), sent massive military aid to Franco in the Spanish Civil War (1936–39), seized Austria (1938), took over Czechoslovakia after the British and French appeasement of the Munich Agreement of 1938, formed a peace pact with Stalin's Russia in August 1939 and finally invaded Poland in September 1939.

On June 30, 1936, Ethiopian Emperor Haile Selassie gave a stirring speech before the League of Nations denouncing Italy's actions and criticizing the world community for standing by.

Japan looked south to expand its empire, which led to conflict with the United States over the Philippines and the control of shipping lanes to the Dutch East Indies.

After taking power, the Nazi government made efforts to establish friendly relations with Poland, which resulted in the signing of the ten-year German–Polish Non-Aggression Pact with the Piłsudski regime in 1934.

In 1939, Hitler claimed extraterritoriality for the Reichsautobahn Berlin-Königsberg and a change in Danzig's status in exchange for promises of territory in Poland's neighbours and a 25-year extension of the non-aggression pact.

In early February in Paris, three pacts were discussed by Polish Chief of State Józef Piłsudski and French President Alexandre Millerand: political, military and economic.

The agreement assumed a common foreign policy, the promotion of bilateral economical contacts, the consultation of new pacts concerning Central and Eastern Europe and assistance in case one of the signatories became a victim of an "unprovoked" attack.

Czechoslovakian foreign policy, under Edvard Beneš, avoided signing a formal alliance with Poland, which would force Czechoslovakia to take sides in Polish–German territorial disputes.

France's reluctance to invest in its allies' industry (especially Poland's), improve trade relations by buying their agricultural products and share military expertise further weakened the alliance.

However, with the German threat becoming increasingly visible in the latter part of the decade, both countries started to seek a new pact to guarantee the independence of all contracting parties and military co-operation in case of a war with Germany.

Although officially called a "non-aggression treaty," the pact included a secret protocol in which the independent countries of Finland, Estonia, Latvia, Lithuania, Poland and Romania were divided into spheres of interest between both the parties.

On September 17, 1939, the Red Army entered Poland from the east, and the Polish Command decided to abandon the defense of the so-called Romanian Bridgehead and evacuate of all its forces to neighboring countries.

In July 1941, as Operation Barbarossa had effectively neutralised the Soviet threat, the faction of the Japanese military junta supporting the "Southern Strategy" pushed through the occupation of the rest of French Indochina.

[71] On 7 December 1941, without a declaration of war,[72] the Imperial Japanese Navy attacked Pearl Harbor with the aim of destroying the main American battle fleet at anchor.

[74] The British declared war on Japan on the morning of 8 December and specifically identified the attacks on Malaya, Singapore and Hong Kong as the cause but omitted any mention of Pearl Harbor.