Excerpts from Books and Wikipedia
"Driven southward, the Song eventually controlled only central and southern China. . . . Trade and industry boomed, and the capital, Hangzhou, became the world's greatest city. . . . Because trade with western lands was curtailed by loss of control over the northern land routes, the Song turned into a maritime power, trading along rivers and by sea with southeastern Asia, Indonesia, India, and Persian Gulf. . . . By 1279, Mongol forces overran the country and ended the Song dynasty." [National Geographic Almanac, p. 134-5] "While the Chinese under the Song perfected the classical examination system as the device for training obedient bureaucrats, the contemporary non-Chinese invaders of China--the Qidan (Liao dynasty), Ruzhen (Jin dynasty), and Mongols (Yuan dynasty)--proved the utility of militarism as the source of imperial power. The ancient adage that China could be ruled only in the Confucian civil fashion is only half true. Imperial Confucianism could function only as long as the ruling dynasty commanded enough violence to destroy rebels, and this type of power was the specialty of the non-Chinese tribesmen of Inner Asia." [Fairbank: China, p. 97-100]