The first Mongol forays into China began around 1000 A.D., but it was not until the arrival of Genghis Khan in 1205 that the Mongols got serious about invading and conquering the empire. After six decades of invasions, Mongol Kublai Khan was crowned emperor of all China in 1279.
In the 13th century, China was divided into two halves, the northern Kin dynasty and the southern Song dynasty. After about a decade of raids by Genghis Khan, the Kin emperor surrendered and agreed to pay tribute.
In 1267, the Mongols decided they wanted the Song dynasty as well. They began invading in the southwest, conquering the provinces of Yunnan and Sichuan. Outflanked, the Chinese steadily lost ground. The last Song emperor, 8-year-old Emperor Bing, died when an attendant leaped from a cliff into the ocean with him to avoid capture.