 The Mongols , a nomadic confederation , had unified in the middle of the twelfth century . They and other steppe nomads occasionally raided the Jin empire from the northwest . The Jin <unk> away from punitive expeditions and was content with <unk> , similar to the practices of the Song . The Mongols , formerly a Jin tributary , ended their <unk> in 1210 and attacked the Jin in <unk> . In light of this event , the Song court debated ending tributary payments to the weakened Jin , but they chose to avoid <unk> the Jin . They refused Western Xia 's offers of <unk> against the Jin in 1214 and willingly complied when in 1215 the Jin rejected a request to lower the annual indemnity . Meanwhile , in 1214 , the Jin retreated from the besieged capital of <unk> to Kaifeng , which became the new capital of the dynasty . As the Mongols expanded , the Jin suffered territorial losses and attacked the Song in 1217 to compensate for their shrinking territory . Periodic Song raids against the Jin were the official justification for the war . Another likely motive was that the conquest of the Song would have given the Jin a place to escape should the Mongols succeed in taking control of the north . Shi <unk> ( <unk> ; 1164 – 1233 ) , the chancellor of Song Emperor <unk> ( r . 1224 – 1264 ) , was hesitant to fight the Jin and delayed the declaration of war for two months . Song generals were largely autonomous , allowing Shi to evade blame for their military <unk> . The Jin advanced across the border from the center and western fronts . Jurchen military successes were limited , and the Jin faced repeated raids from the neighboring state of Western Xia . In 1217 , the Song generals Meng <unk> ( <unk> ) and Hu <unk> ( <unk> ) defeated the Jin and prevented them from capturing <unk> and <unk> . 
