Civil Engineering genius Fritz Todt(father of the autobahn) ran the numbers and found out it was impossible for Germany to win the war militarily

At Dunkirk, Guderian defied Hitler's orders and moved to attack the defeated Allied force at Dunkirk, but Hitler angrily told him that if he did not immediately halt his tanks' advance, Guderian would be court-martialed - or worse. Hitler failed to develop long-range bombers, evidently couldn't figure out that his radio codes had been compromised, built narrow-track Panzers to invade the Soviet Unuon's deeply-muddied terrain (the Russian tanks were designed with wide tracks to move more easily through mud and over snow). Most of all, the man never had a solid plan to obtain enough oil for his military offensives. Syalingrad was lost because only a fraction of supplies could be elivered as most Luftwaffe planes could not obtain fuel.