On September 1, 1939 the German Army invaded Poland.
The Germans used a strategy called "Blitzkrieg" against the Poles. The "Blitzkrieg" or "Lightning War" uses fast attacks with tanks and mobilized infantry along with heavy bombardment with artillery. The use of aircraft is also present to provide air superiority and to prevent the enemy from resupplying and also the redployment of more enemy troops.
With the use of Blitzkrieg warfare and superior weaponry the German Army had defeated the Polish Army within weeks.
When confronted by the leaders of England and France, Hitler said it was a defensive action.
The truth was that it would provide "living space for the racially superior Germans".
Hitler's plan was, after Germany successfully invades and controls Poland, the Germans would colonize Poland and the native Slavic people would be enslaved.