Yin Mountains
Earlier in 1204, Genghis Khan had subdued the Ongud, a Mongol tribe helping the Jin dynasty guard its northern border. At the same time, Genghis Khan also formed an alliance with the Ongud by marrying his daughter to the Ongud chief's son. The Mongols controlled the area north of the Yin Mountains and started stockpiling resources in preparation for a military campaign against the Jin dynasty. Moreover, the Mongols had also been actively luring and inducing some Jurchens to defect or surrender. The Jin emperor Xingsheng underestimated the Mongol threat and had been gradually neglecting the defences against the Mongols. He was also delusional in his belief that the Jin dynasty was far more powerful than the Mongols.