What made Germany’s invasions of Europe difficult to stop during World War II?

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What is the main social system that existed in ancient china?

How did african americans the union during the civil war? a. by serving as representatives in congress b. by enlisting in the military to fight c. by organizing massive slave revolts in the south d. by negotiating for peace with the confederacy

Brainliestttme : describe the following event: increase in islamic extremism in the middle east