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What Started WW2? Military Causes

Although a variety of different factors caused World War Two, the main event and the trigger for what started WW2 was Germany’s invasion of Poland in September 1939.

“The Causes of World War 2”

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Of course the invasion was preceded by decades of political conflict. The Treaty of Versailles, signed at the end of WW1, placed some very harsh restrictions on Germany, which created a feeling of resentment among the Germans. Due to the financial depression of the 1920’s, Germany simply did not have the funds to pay the reparation fees demanded by the treaty. This could well have bene the foundation for what started WW2.

Other countries were sympathetic and acted very lenient towards Germany, overlooking other clear violations of the Treaty, such as a union with Austria. They also decided not to interfere when Hitler began to expand his army and, afraid of starting another war, did nothing when he claimed back former German land from Czechoslovakia. When they however realized that Hitler was setting his sights on Poland in his plight to expand his empire, this was the last straw. As soon as Hitler attacked Poland, Britain and France declared war against Germany.

Explanations from Propaganda

What started WW2? For those wondering how Hitler managed to get the German nation to support the invasion of Poland; Hitler did some very clever marketing in the form of propaganda. While the practice of manipulating public opinion is a mainstay of any political party today, it was an innovative practice in the early Twentieth Century. Nobody perfected this practice better than the Nazis, who devoted entire offices to propaganda and treated it with the same scientific thoroughness as weapons research.


Months before the 1939 invasion of Poland, Hitler and the German press accused the Polish of performing violent “ethnic cleansing” of Germans that were living in Poland. Adolf Hitler also ran several false flag operations such as the Gleiwitz incident, where he dressed his own men in Polish uniforms and ordered them to attack German stations. Needless to say, the Germans believed that Germany had to retaliate and that war with Poland was justified. This could serve as a partial answer to the question of what started WW2.

This article is part of our larger educational resource on World War Two. For a comprehensive list of World War 2 facts, including the primary actors in the war, causes, a comprehensive timeline, and bibliography, click here.

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