Answer:
The German invasion of Poland officially began the fighting of WWII in Europe though Germany had already began annexing parts of countries and even whole countries (i.e. Hungary) through appeasement from the UK and France. The invasion of Poland was the first official declaration of war in Europe which caused a chain reaction. Because Poland was aligned with the UK and France, they also declared war on Germany though they did little to stop Hitler's forces from steamrolling through Polish lines. The leaders of the UK and France were weary to be involved in yet another world conflict and the Nazis, being fully aware of this, took advantage and Blitzkrieged through the low countries. Thus, the conflict in Europe had began.
