In a nutshell , it was the Conviction-of-the-Commonwealth that it was Right to fight this tyranny Hitler had created in Europe, and the threat to the Freedom of the Free World. After the Great War , another Generation of Young People saw a Job that had be done , and enlisted. We lost in France and consolidated back in Britain. By then, Commonwealth troops were assembling and the Atlantic and Dominion convoys reinforced the Battle of Britain. - The rest has been said ; Radar , Hitler as C-in-C and his decisions Cost Germany the War. But the Grit to Fight back that came from that Generation of The Allies , won the War. - It was Churchill that stirred 'em up too. - Do you think Today's Generation could do the same thing , if asked ???