My thought would be if when Adolf Hitler and the NSDAP went around Germany and instead of blaming the Jews for the loss of WWI instead blamed the British and French for the horribly unfair Versailles Treaty. And made every German (Aryan, Jew, etc) truly believe in Ein Volk, Ein Reich, Ein Fuhrer. Thereby not having wasted manpower killing "Untermensche" and also scientists like Albert Einstein neve leaving Germany. This also would make WWII be a war to Regain Germany's lost territories and be a war where all Germans fought for the Fatherland