7.6F: Causes of WWII

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Learning Objective 7F

Explain the causes and consequences of World War II.

Historical Development 1

The causes of World War II included the unsustainable peace settlement after World War I, the global economic crisis engendered by the Great Depression, continued imperialist aspirations, and especially the rise to power of fascist and totalitarian regimes that resulted in the aggressive militarism of Nazi Germany under Adolf Hitler.


World War 2 Background


September 1, 1939 – September 2, 1945


Fighting in World War II was more widespread than fighting in World War I. The two largest theatres of fighting were in Europe and East Asia. However, significant conflict also erupted across North Africa and the Middle-East. 


World  War II had two military alliances. The Axis Powers of Italy,  Germany, and Japan. The Allied Powers were England, France, Russia, and the United States. Nations with colonies required their colonies to provide resources and soldiers for the war effort. 


World War II is often viewed as a continuation of World war I that resulted because of the failed peace after World War I. This total war was fought with 100 military personal from over 30 countries. By the end of the war, at least 70 million people had been killed. 


The Allies fought in Europe to prevent the spread of fascist Germany across Europe, especially Eastern Europe. Japan fought in Europe for the expansion of the Japanese imperialism. America entered the  war following Japan’s attack on the American naval base in Pearl harbor, Hawaii on December 7, 1941. 


The war ended with an Allied victory and the fall of Nazi Germany, fascist Italy, and Imperial Japan.  Over 70 million, people across the world died.  Allied nations created new international institution, such as the United nations, to mange global relationships. The United States and the Soviet Union rose at the new global superpowers. 

The Axis and Allied powers

The Axis Powers

Major Axis powers 

  • Germany 
  • Italy
  • Japan

Other Axis powers 

  • Hungary
  • Romania 
  • Finland 

The Allied Powers

The Big Three 

  • The United Kingdom (and colonies) 
  • The Soviet Union (from June 1941)
  • The United States (from December 1941)

Other significant Allied Powers 

  • France
  • China 
  • India (British colony)
  • Australia 
  • New Zealand 
  • South Africa
  • Brazil 
  • Mexico
  • Belgium (after liberation)
  • Netherlands (after liberation)

What were the causes of World War II?

After WWI, many argued that humanity had fought its last war. However, just 20 years later, a second global war broke out. World War II surpassed the death and destruction seen in WWI. By the end of the war, 80 million people were dead, nearly 3% of the world’s population. The causes of WWII included the unsustainable peace settlement after WWI, the Great Depression, imperialism, and the rise of fascist and authoritarian powers like Nazi Germany.

Cause 1: The Treaty of Versailles

The Treaty of Versailles did not bring lasting peace but instead set up the conditions that led to WWII.

Why did the Treaty of Versailles fail to bring peace?

Historians generally argue that the English and French used the Paris Peace Conference and the Versailles Treaty to punish the losing nations with severe consequences that crippled the losers’ societies and prevented them from creating stable political and economic systems after the war. The treaty only blamed the losing side and did not require the French and British to consider what role they may have played in creating the conditions that led to the war. As a result, the losing nations, especially Germany, were humiliated and angry at their harsh treatment.

War guilt clause: Germany had to take full responsibility for the war.

Loss of colonies: Germany had to agree to give up its colonies and portions of its territory in Europe. The Treaty forced Germany to give up territory to Belgium, Czechoslovakia, and Poland and return Alsace and Lorraine to France.

Financial reparations: Germany agreed to pay billions of dollars in financial reparations (repayments for a wrong). Reparations destroyed the German economy and prevented the German government from having the money necessary to rebuild Germany and stabilize its economy. After the war, Germany suffered from high inflation that made many essential goods like bread and milk unaffordable.

Limits on armed forces: Germany also had to reduce the size of its military. The entire army was limited to 100,000 soldiers, and the nave just 15,000. Along with setting restrictions, the Treaty also restricted the German government from manufacturing submarines, tanks, warplanes, poison gas.

German people blame the Weimer government: Germany’s postwar government, known as the Weimar Republic, signed the Treaty. The German people resented the Weimer government for accepting the Treaty, which contributed to the rise of the fascist Nazi party and Adolf Hitler.

Cause 2: economic depression

Economic depression in Germany after WWI and the global Great Depression of 1929 led to declining living standards. As people’s suffering increased within the industrial nations, political instability increased.

  • Populations became more open to radical leaders who blamed groups for economic conditions and offered radical changes to improve economic conditions.
  • This openness to alternative voices gave extremists a microphone to preach fascist and authoritarian ideas that blamed society’s troubles on specific groups.
  • Hitler was democratically elected and appointed the leader of Germany in 1933. He rose to power using an openly anti-Jewish campaign that blamed Jews for Germany’s economic troubles.

Cause 3: fascist and authoritarian governments

Fascist political leaders came to power in the 1920s and 1930s in Italy, Germany, and Spain. Promoting the strength and glory of the state was of utmost importance in fascist systems. Fascist regimes violently repressed all political opposition. Fascist governments banned all political opposition and eliminated speech and media freedoms.

Mussolini in Italy

Benito Mussolini was Europe’s first fascist dictator. He and his supporters took control of the Italian parliament in the mid-1920s, riding on a wave of general social discontent, which included the belief that the great powers had disrespected Italy at the Paris Peace despite Italy being on the winning side.

Hitler in Germany

Adolf Hitler rose to power in early 1930s Germany. Like Mussolini, Hitler came to power promising to rebuild the glory of Germany from the embarrassment and unjust treatment of the Versailles Treaty. He came to power through legal democratic processes. However, he used his authority to overthrow Germany’s democracy and seize absolute power.

Franco in Spain

Spain fell into civil war in the 1930s. When the war ended, fascist leader Francisco Franco defeated the Republic of Spain. While Spain never officially entered WWII, Franco did provide some assistance to Mussolini and Hitler. Franco retained power in Spain until 1975.

Authoritarianism in Japan

The Meiji reforms of the late 19th century transformed Japan into a constitutional monarchy. While technically democratic, a small, powerful elite ruled Japan. As Japan became increasingly angry at the western refusal to view them as an equal partner, Japanese nationalism surged. Conservative forces completely took over the government in the 1930s and adopted militaristic policies that viewed expansion as the best way to protect Japan. Authoritarian leaders silenced opposing voices.

Cause 4: militarism

Fascist governments in Europe and authoritarian leaders in Japan were militant nationalists. They glorified the military, combat, and dying for the nation. They devoted significant portions of their nation’s gross domestic products (GDP) to enlarging their armies and building modern weaponry and fighting forces.

Militarism in Germany

When Hitler came to power, he immediately went about rebuilding the German military in violation of the Versailles Treaty. He strengthened the army by

  • increasing the number of troops in the army,
  • developing a new air force,
  • and rebuilding the German navy,

Other western powers did nothing to stop him, hoping that a more powerful German military might halt the spread of communism out of Russia. By the mid-1930s, Hitler possessed one of the largest and strongest industrial militaries in the world.

Militarism in Japan

Throughout the 1930s, the military gained increasing power within Japan’s democratic institutions. Military leaders increasingly set Japan’s sights on foreign targets and empire building.

  • Japanese leaders saw themselves as facing two potential enemies. One was the communist Soviet Union, and the other was the western industrialized nations, such as the United States.
  • As military leaders gained power within the government, they funneled ever-increasing resources into expansion and building the Japanese war machine.
  • The state was also able to effectively use propaganda to sway Japanese public sentiment toward supporting the empire’s overseas conflicts by linking the success of the homeland to military conquest.

In 1941, military general Hideki Tojo became the Japanese Prime Minister. Less than two months later, Japan attacked the American Naval base in Pearl Harbor on December 7, 1941, drawing America into WWII.

Cause 5: imperialism

One feature of WWII fascism was an obsession with expanding the states’ territory and power, especially into the regions of those deemed “inferior” races.

Italian imperialism

After becoming the leader of Italy, Mussolini expanded the Italian empire.  

  • 1927: Albania became an Italian protectorate.
  • 1936: Italy invaded and defeated Ethiopia, one of the few places in Africa that had managed to retain its independence following the Scramble for Africa. Mussolini combined this territory with the pre-existing Italian colonies of Somaliland and Eritrea.
  • 1939: Italy invaded and annexed (combined with) Albania into Italy.

German imperialism

Once in power, Hitler sought to build a German empire closer to home. He became obsessed with expanding German living space in Central and Eastern Europe (Lebensraum). Hitler sought the permanent removal of Poles, Ukrainians, Russians, Czechs, and other Slavic people from the conquered lands. Germans and pure Aryans would settle conquered territories.

  • 1938: Hitler annexed the Czechoslovakian Sudetenland. Italy and France approved this land grab at the Munich Conference.
  • 1939: Hitler invaded the whole of Czechoslovakia and split it into two pieces. The western portion of Bohemia and Moravia were proclaimed a German protectorate and occupied by German forces. The eastern part of Czechoslovakia became independent and allied with Germany.
  • 1939: WWII officially started after Hitler invaded Poland and France and England declared war on Germany.
  • 1941: Hitler later violated his treaty with the Russian leader Stalin when he attacked Russia.

Japanese imperialism

Japan’s imperial ambitions to create an East Asian empire grew in the 1930s and led to the Greater East Asian Co-Prosperity Sphere.

  • 1931: Japan invaded Manchuria in Northern China.
  • The 1930s and early 1940s: Throughout WWII, Japan invaded European colonies throughout Southeast Asia. The Philippines, Malaysia, Vietnam, Cambodia, Myanmar were either attacked or occupied by Japan.