Why hitlers invasion of the soviet union was one of his biggest military mistakes

Hitler did not have the strength he thought he did.

Explanation:

Hitler had an allience with Russia, but when he got extra greedy, he decided to attack Russia. Of course, being that he attacked them in the winter did not help. Hitler's army way not equipped well enough to survive the harsh Russian winters, resulting in much of his army freezing or starving to death.

I hope this helps!!! Here's an article that might help:

https://www.historyextra.com/period/second-world-war/operation-barbarossa-hitlers-greatest-mistake/

tearing down the berlin wall.