Two thousands years ago, china was unified by qin dynast followed by han dynast. During this period, china conquered nanyue kingdom (approximately Guangdong province of china today), Vietnam, Korea. Today, Guangdong is a part of china, but Vietnam and Korea are independent nation. Before the western country came to east Asia, the two country adopted Chinese writing system, Chinese political system, Chinese culture and so on. But why the Korea and Vietnam are different from Guangdong(nanyue kingdom)?