The cessation of fighting against the Sung brought no real advantage in external affairs, though the tribute payments appealed to the greed of the rulers and were therefore welcomed. There could be no question of further campaigns against the south, for the Hsia empire in the west had not been destroyed, though some of its territory had been annexed; and a new peril soon made its appearance in the rear of the Chin. When in the tenth century the Sha-t'o Turks had had to withdraw from their dominating position in China, because of their great loss of numbers and consequently of strength, they went back into Mongolia and there united with the Ta-tan (Tatars), among whom a new small league of tribes had formed towards the end of the eleventh century, consisting mainly of Mongols and Turks. In 1139 one of the chieftains of the Juchên rebelled and entered into negotiations with the South Chinese. He was killed, but his sons and his whole tribe then rebelled and went into Mongolia, where they made common cause with the Mongols. The Chin pursued them, and fought against them and against the Mongols, but without success. Accordingly negotiations were begun, and a promise was given to deliver meat and grain every year and to cede twenty-seven military strongholds. A high title was conferred on the tribal leader of the Mongols, in the hope of gaining his favour. He declined it, however, and in 1147 assumed the title of emperor of the "greater Mongol empire". This was the beginning of the power of the Mongols, who remained thereafter a dangerous enemy of the Chin in the north, until in 1189 Genghiz Khan became their leader and made the Mongols the greatest power of central Asia. In any case, the Chin had reason to fear the Mongols from 1147 onward, and therefore were the more inclined to leave the Sung in peace.
In 1210 the Mongols began the first great assault against the
Chin, the moment they had conquered the Hsia. In the years 1215-17 the Mongols took the military key-positions from the Chin. After that there could be no serious defence of the Chin empire. There came a respite only because the Mongols had turned against the West. But in 1234 the empire finally fell to the Mongols.
Many of the Chin entered the service of the Mongols, and with their permission returned to Manchuria; there they fell back to the cultural level of a warlike nomad people. Not until the sixteenth century did these Tunguses recover, reorganize, and appear again in history this time under the name of Manchus.
The North Chinese under Chin rule did not regard the Mongols as enemies of their country, but were ready at once to collaborate with them. The Mongols were even more friendly to them than to the South Chinese, and treated them rather better.