China
During the later years, China was often raided or invaded by northern nomadic people such as the Xiongnu, the Xianbei, the Jurchens and the Mongols (the latter led by Genghis Khan and Kublai Khan). One effect of regular nomadic invasion and the collapse of native dynasties was the massive migration of Han Chinese - especially the aristocratic elite and the literati, to sparsely populated frontier regions south of the Yangzi river such as Jiangsu, Zhejiang, Guangdong and Fujian. Several notable waves of Han Chinese immigration to Jiangsu, Zhejiang, Guangdong and Fujian took place during the collapse of the Jin, the Tang, and the Song.