While the Jin and Song dynasties confronted each other along the Yangtze River, an obscure nomadic tribe was quietly rising in the northern grasslands under Jin rule. in 1206 Temujin, who now became Genghis Khan, announced the founding of the Mongol Empire.Mongol cavalry swept down to the Jin Dynasty, Western Xia and Tubo .... The powers of East Asia fell in droves.

World in 1235 AD
Under the leadership of Genghis Khan, the Mongols, originally vassals of the Jin dynasty, rose in rebellion in 1211. The war between the two sides lasted for 24 years. in 1227, after attacking the Western Xia, Genghis Khan died and his third son Voghtai took the throne. voghtai devoted all his Mongol forces to attacking the Jin dynasty and in 1232 allied with the Song dynasty and the two sides attacked the Jin dynasty together. in September 1233, the Song-Mongol allied forces besieged Cai Zhou, the last bastion of the Jin dynasty.
In February 1234, the city ran out of food and its walls were destroyed by the allied forces. Emperor Wanyan Shousu passed the throne to Marshal Wanyan Chenglin and ordered him to break out in order to hold out for battle.
On 9 February, the new emperor was in the process of being crowned when the Song and Mongolian armies had break into the city. The new emperor led his troops in street battle after the ceremony was completed and was killed,bringing about the end of the Jin dynasty.