The great wall of china and the berlin wall of both intended to

Oh, goodness.
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WEST BERLIN    EAST BERLIN
WEST BERLIN    EAST BERLIN
WEST BERLIN    EAST BERLIN
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You see, East or else West (I don't remember) Berlin was Communist. The other was not Communist. One side of China was China, and the other side... well, invaders' land.
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You see, China was tired of Mongols attacking them, and Communist Berlin tired of their people escaping to non-Communist Berlin.
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So, they built a wall to prevent people from escaping and prevent people from getting in.
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Both prevented people from entering or leaving, in a sense.