The primary reason for the construction of the Great Wall of China was to protect the Chinese states and empires from invasions by nomadic tribes from the north, particularly the Mongols. Initially built during the 7th century BCE and expanded significantly over the centuries, the wall served as a defensive structure to help control trade routes and immigration, as well as to provide military outposts. Its construction spanned several dynasties, with the most famous sections built during the Ming Dynasty (1368–1644). The Great Wall is not just a military fortification; it symbolizes the unification and strength of the Chinese people in the face of external threats.