What started World War 2 and when?

Answer 1

The build up to WWII was done on several fronts: Hitler had claimed parts of Chechoslovakia and invaded it without outbreak of global war, and Austria was annexed to Germany. The Germans said that they wanted justice for WWI e.g. restoring former German territories and "Lebensraum" especially where many Germanspeakers lived. Italy had conquered African territories and Japan had been warring in China since mid 30s. These three made a tripartite "Axis pact" as a continuation of the "pact of steel" (Hitler-Mussolini).

Adolf Hitler gave the order for German troops to attack Poland in the morning of 1/9 1939, announced as a "retaliation to Polish aggression". According to the Molotov-Ribbentrop pact Poland was divided between Hitler and Stalin beforehand, and thus the Red Army soon invaded Poland simultaneously with the Werhmacht. Also Mussolini was prepared to this war. As the UK had an agreement with Poland, the WWII was a fact when UK and France declared war against Germany 3/9, and the war started to become global. Most countries were neutral in the beginning, trying to escape the hell of war, but in 1940 most of Europe was affected and largely under German rule. So in June 1941 it was basically Britain with its commonwealth that stood alone against Hitler, Mussolini, Stalin and Hirohito, when France was ruled by nazifriendly Pétain. But Britain's involvement in Africa and Asia brought the conflict to the colonial areas, e.g. Egypt and Burma, making it truly global in 1941 and not only on European soil. Hitler and Stalin had been discussing in 1940 how to divide the British territories between them but that ended with operation Barbarossa.

Answer 2

World War 2 started on september 1st 1939 when Britain and France declared war on germany. France and Britain declared war on germany because hitler sent 1 million troops to invade poland along with another 500,000 in support during the invasion. Germany invaded poland because Germany wanted to reclaim it's land what they lost because of the Treaty of Versailled which was signed when germany lost World War 1 the the Allied Forces.