this answer starts at the beginning, Hitler should have built up his military might more before going to war with Poland/Europe. Defeating the Bolsheviks/Communism were the Nazis highest priorities but they had to ally with them at beginning or else they could have faced a two-front war, Hitler knew this and in the back of his head he was waiting for the perfect opportunity to strike. Saying this it confuses me still why he decided to forsake England a enemy that was no where near being defeated and were allied with us a sleeping giant, didn't he know that sooner or later they were going to invade France with superior forces? yes he had the beaches mined and built the bunkers ect... for a invasion but why not just finish off England? Yes it was a stalemate military wise, England was ready for a invasion from the Germans and they had a good navy. But Hitler wasn't counting on Englands harassment, they wouldn't leave him alone, he thought he could ally with them thats why Rudolf Hess flew over to negotiate, he realized they posed a grave threat to the Third Reich. Operation Sealion shouldn't have been post-poned, it should have been either re-planned or executed not delayed. Once England was removed then regather strength, build-up and finally invade the Soviets knowing you won't be fighting a two-front war. And yes Barbarossa should have began at that date, then the winter wouldn't have been has bad. Napoleon made the same mistake.