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