What caused World War II to break out in 1939?

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pohnpei397's profile pic

Posted on

The immediate cause of the outbreak of WWII in Europe in 1939 was the German invasion of Poland.  England and France had guaranteed that they would protect Poland’s borders as they were in 1939.  When Germany invaded, France and England kept their promise and declared war.

The broader cause of the war was German aggression and French and British appeasement.  Germany, under Hitler, had been trying to expand and create what it saw as a Greater Germany that included all ethnic Germans.  The French and British had simply allowed this expansion, not doing anything when Germany annexed Austria and then took Czechoslovakia.  Since the allies did not act, Hitler was emboldened to take Poland as well, not believing England and France would go to war.

However, England and France decided they could no longer back down and they went to war when Germany invaded Poland.

gpane's profile pic

Posted on

As outlined in pohnpei's answer, Germany's expansionist aims in Europe were the immediate trigger of the Second World War, when Britain and France stepped in following the German invasion of Poland.

Of course, it should be remembered that German expansionism had its roots in the outcome of the First World War, when Germany was stripped of land and power by the victorious nations, chiefly Britain and France. There was simmering resentment among many in Germany about how the country had been treated, and Hitler was able to exploit these grievances as he talked up the cause of German nationalism. The ignominious fate of Austria -  another Germanic country and formerly the seat of a centuries-old European empire - in the First World War also played into this.

The antagonism between these Germanic powers and Britain and France really went back to the nineteenth century when the ascendant German kingdom of Prussia unexpectedly defeated France in war. France and Britain were long-standing imperial powers in Europe (and had often bitterly fought each other) but in the later nineteenth century Germany began to seriously challenge them both. This rivalry between major European nations and the concomitant arms race was in large measure responsible for World War I, and the after-effects of that war carried over into World War II.

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