The main cause of the Great Wall of China's construction was to protect Chinese states and empires from invasions by nomadic tribes, particularly the Mongols. The wall's beginnings can be traced back to the 7th century BC, but it was most significantly expanded during the Ming Dynasty (1368-1644). The wall served as a formidable line of defense against military incursions and a means of regulating trade along the Silk Road. Beyond military purposes, it symbolized the strength of the Chinese state and its resolve to defend its territory and culture from outside influences.