What events led to the outbreak of World War II?

Answer:
Hitler invaded Poland and two days later, France and Britain declared war on Germany, beginning World War II
Explanation:
Answer:
In short, the violation of the treaty of Versailles and the invasion of Poland
Explanation:
Hitler directly violated the treaty by remilitarizing the Rhineland and building up the German military. This had tensions high in Europe. When Hitler invaded Poland in September 1939 the French declared war on the reich which in turn the UK joined.