The Beginning
After establishing neutral foreign policy with the Soviet Union, Hitler unleashed his troops on Poland in 1939.
"Chamberlain... proclaimed Britain was at war with Germany, after the expiration of the British ultimatum to Germany to withdraw her troops from Poland. The deadline expired at 2 a.m., Pacific Time. 'No one can imagine what a bitter blow it is to me. The actions of this man Hitler show convincingly that he will never do otherwise than use force in the attainment of his will. Consequently, we are at war with Germany. I am certain right will prevail,' Chamberlain said in his fateful message, which was broadcasted in a quarter of an hour radio address... France... joined Britain in war against Germany. The French government announced Germany's refusal to answer to France's ultimatum for withdrawal of Reich troops from Poland, automatically putting France at war starting at 7 p.m., Sunday, Paris time. Australia, New Zealand and Egypt followed next in declaration of war against Germany."
-Fairbank's Daily New in Alaska, September 4, 1939
The refusal to accept their ultimatums resulted in a war waged between Germany and most of the world. Thus, began World War II.