 In February 1233 , the Mongols took Kaifeng after a siege of more than 10 months and the Jin court retreated to the town of Caizhou . In 1233 Emperor <unk> ( r . 1224 – 1234 ) of the Jin dispatched diplomats to <unk> the Song for supplies . Jin envoys reported to the Song that the Mongols would invade the Song after they were done with the Jin — a forecast that would later be proven true — but the Song ignored the warning and rebuffed the request . They instead formed an alliance with the Mongols against the Jin . The Song provided supplies to the Mongols in return for parts of Henan . The Jin dynasty collapsed when <unk> and Song troops defeated the Jurchens at the siege of Caizhou in 1234 . General Meng Gong ( <unk> ) led the Song army against Caizhou . The penultimate emperor of the Jin , Emperor <unk> , took his own life . His short @-@ lived successor , Emperor Mo , was killed in the town a few days later . The Mongols later turned their sights towards the Song . After decades of war , the Song dynasty also fell in 1279 , when the remaining Song loyalists lost to the Mongols in a naval battle near Guangdong . 
