Because each month spent “trusting Hitler” was a month spent by Marshal Timoshenko to ensure learning of some more soldiers to actually shoot. The problems were that bad...
Now, putting the airplanes in positions more suitable for attacking Germany than defending from it (so they were quickly destroyed on the 21 June) was a big mistake from the Soviet side.
You need to read Churchill, Hitler and the Unnecessary War.
BTW How is trusting Hitler not a “massive external error”?
Because each month spent “trusting Hitler” was a month spent by Marshal Timoshenko to ensure learning of some more soldiers to actually shoot. The problems were that bad...
Now, putting the airplanes in positions more suitable for attacking Germany than defending from it (so they were quickly destroyed on the 21 June) was a big mistake from the Soviet side.