Originally Posted by Fooldartz
But everything he did was strategically sound until he invaded Russian Europe. Or am I just an idiot?
Hitler's strategies had nothing to do with early German successes - all the actual work was done by his generals. Besides, the German armed forces outmatched those of Britain and France at the start of the war (if not in actual material strength then in doctrine, morale and tactics). Germany was fighting at an advantage at the start of the war because their opponents were either unprepared for war (Britain and France) or simply didn't have the resources to match Germany's war machine (Poland).
So, Germany was more than capable of conquering continental western and central Europe. This was the zenith of Germany's success not because Hitler suddenly started making stupid decisions, but because the next round of fighting would be with enemies Germany had no realistic hope of defeating: the USSR and the USA. To be fair, if Germany had played its cards better the USSR might have folded in 1941, but it was a long shot. The sheer logistical strain of invading the USSR had broken the back of the German armed forces by 1942, and the resulting war of attrition was unwinnable for the Nazis given that the USA was now pouring nearly limitless resources into the war effort of both Britain and the USSR.
People often cite the opening of hostilities between Germany and the USSR as Hitler's "big mistake", but from their viewpoint it would have been an even bigger mistake not to invade the USSR. By the 1940s the USSR was knee-deep in militarization and the officer corps of the Red Army was being quickly rebuilt after being eviscerated in the 1930s. Hitler and the generals knew that the chance of victory over the USSR became slimmer every year the invasion was delayed.