The South and East China Seas served as vital maritime highways, connecting China with Southeast Asia, India, the Middle East, and Europe. Ports like Guangzhou and Quanzhou became cosmopolitan hubs, facilitating the flow of goods, technologies, and ideas.
China's seas also exposed it to maritime threats, particularly from the north and east. This prompted the development of naval forces and coastal fortifications (e.g., the Ming coastal defense system) to protect against invasions and piracy.