World War II was caused by a number of factors both long term and short term.
The Treaty of Versailles was signed after World War I, by the Germany. The German people were angry at the punishments, which included paying reparations and reducing the German Army to 100,000 men. Hyperinflation during the Weimar period meant that it was not uncommon to see people with stacks of worthless money in wheelbarrows, which was used to light fires not spending!
Hitler and the Nazi Party used this resentment to boost their rise to power.
Rearmament and expansion
Hitler rearmed the German military, going against the clauses in the Treaty of Versailles. He used his propaganda machine, promising that Germany would be strong again.
In 1936 he moved troops into the demilitarised Rhineland, and yet Britain and France did nothing. In 1938 he united Germany with Austria which was called Anschluss. Again this was against the Versailles treaty, and nothing was done.
Czechoslovakia bordered next to Germany. Hitler argued that because there was a large population of Germans in the west part of the country that a part of it should go back to the nation. On September 30, 1938 the Munich agreement was signed. The British Prime Minister Neville Chamberlain had given away the Sudetenland, the industrial part of Czechoslovakia to Nazi Germany. This was a controversial move chosen as a strategy to satisfy Hitler and to gather time to build up Britain’s forces.
Invasion of Poland on September 1, 1939
On September 1, 1939 Nazi Germany invaded Poland. Germany’s Blitzkrieg ‘lightning war’ tactic of using planes, tanks and infantry on the enemy overwhelmed the Polish troops. By the end of the month on September 27, Poland had already surrendered.
Britain and France declared war on Nazi Germany beginning the Second World War.