Having to pull Mussolini's arse outer of the fire from his ill-timed and ill-advised incursion into Greece which delayed the jump off for Barbarossa by 6-8 weeks coupled with an earlier starting (by 3 weeks) and much much colder and harsh than usual Russian winter certainly didn't help. Although Hitler, by all accounts from unclassified wartime documents, was responding and pre-empting a Russian/ Stalin betrayal of Russia already massing troops on their border to invade into Germany. Potato potatoe.
Stalling Germany forces and Allowing the BEF to evacuate from Dunkirk and leaving the entirety of the Afrika Korps and equipment in North Africa. Imo the slow response to D Day was more important and ultimately detrimental.
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