Why is there a historical debate surrounding the great wall of china?

The Great Wall of China is, as the name suggests, a wall built to protect China from foreign invasions. The actual length of the wall is debatable but measurements range from 1.500 miles to 4.000 miles.

This is one of the debates about the wall. How long it actually is, since some historians consider some parts of the construction, while others leave some parts out of the count. Also, the wall wasn't built altogether, so it opens the debate whether or not some parts of it were actually parts of the Great Wall.

The other debate is whether or not it served its purpose of defending the land. Back then, armies had way less technology and resources to use during wars, so the wall was the primary tool for protection. However, some historians argue that it may not have been as effective as it was first intended to be.

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