What was the reason for the great wall of china?

The Great Wall of China was built as a military defensive line to defend the invasions from some northern nomadic nations. Apart from the function of defense, the wall also boosted the economy, as well as promoted the culture exchange and national integration of different nations at its two sides.

Explanation:

(202 bc - 220 ad) dynasty started by lui bang; a great and long-lasting rule, it discarded the harsh policies of the qin dynasty and adopted confucian principles; han rulers chose officials who passed the civil service exams rather than birth; it was a time of prosperity

explanation:

i have ni idea