bro I played hoi4 so I'm an expert on ww2, I could've won that shit in 10mins
1. Not turning back to destroy the British at Dunkirk
2. Failing to secure enough oil both before and during the war (this was a MASSIVE problem)
3. Wasting resources on invasion of Norway
4. Dividing forces in 3 rather than in 2 while invading USSR, capturing Leningrad didn't serve much of a purpose, should have pushed towards the Volga valley as that contains majority of Russia's population & factories
5. Failing to build a strategic bomber force that could have taken out Soviet war material production in the Volga valley
6. Wasting enormous resources trying to capture cities like Stalingrad. Should have just bypassed them but hit the factories from overhead.
7. By far the biggest problem was not having enough tanks, planes, truck etc to compete with USA/UK/USSR. They simply didn't have enough resources or factories to match up. But if they fixed the above flaws, they could win before this really started to kill them.
8. Having a horse-drawn supply system rather than truck based like ALL of the allies did. This goes back to NO OIL. Worked ok in France but the USSR was just way too deep to get supplies that far.
9. Not providing adequate winterization for troops, tanks etc for the winter of 41-42. Dumb mistake, did they all just expect to go home the second Moscow fell?
10. Could have knocked out France by Nov 1939 in order to invade Russia earlier
11. Delayed invasion of Russia until June 41, should have been April