The feeble emperor Wu Tsung died in 1521, after an ineffective reign, without leaving an heir. The clique then in power at court looked among the possible pretenders for the one who seemed least likely to do anything, and their choice fell on the fifteen-year-old Shih Tsung, who was made emperor. The forty-five years of his reign were filled in home affairs with intrigues between the cliques at court, with growing distress in the country, and with revolts on a larger and larger scale. Abroad there were wars with Annam, increasing raids by the Japanese, and, above all, long-continued fighting against the famous Mongol ruler Yen-ta, from 1549 onward. At one time Yen-ta reached Peking and laid siege to it. The emperor, who had no knowledge of affairs, and to whom Yen-ta had been represented as a petty bandit, was utterly dismayed and ready to do whatever Yen-ta asked; in the end he was dissuaded from this, and an agreement was arrived at with Yen-ta for state-controlled markets to be set up along the frontier, where the Mongols could dispose of their goods against Chinese goods on very favourable terms. After further difficulties lasting many years, a compromise was arrived at: the Mongols were earning good profits from the markets, and in 1571 Yen-ta accepted a Chinese title. On the Chinese side, this Mongol trade, which continued in rather different form in the Manchu epoch, led to the formation of a local merchant class in the frontier province of Shansi, with great experience in credit business; later the first Chinese bankers came almost entirely from this quarter. After a brief interregnum there came once more to the throne a ten-year-old boy, the emperor Shen Tsung (reign name Wan-li; 1573-1619). He, too, was entirely under the influence of various cliques, at first that of his tutor, the scholar Chang Chü-chan. About the time of the death, in 1582, of Yen-ta we hear for the first time of a new people. In 1581 there had been unrest in southern Manchuria. The Mongolian tribal federation of the Tümet attacked China, and there resulted collisions not only with the Chinese but between the different tribes living there. In southern and central Manchuria were remnants of the Tungus Juchên. The Mongols had subjugated the Juchên, but the latter had virtually become independent after the collapse of Mongol rule over China. They had formed several tribal alliances, but in 1581-83 these fought each other, so that one of the alliances to all intents was destroyed. The Chinese intervened as mediators in these struggles, and drew a demarcation line between the territories of the various Tungus tribes. All this is only worth mention because it was from these tribes that there developed the tribal league of the Manchus, who were then to rule China for some three hundred years.