Mongol conquest of China

The Mongol Conquest of the Song Dynasty was an invasion of the Song states in southern China by the Mongol Empire led by Möngke Khan and later Kublai--both grandsons of Genghis Khan.

The resistance of the Song army in Sichuan was ineffective. By the spring of 1259, Möngke reached the city of Hechuan. In order to take Hechuan, the Mongols had to capture the Diaoyu Castle.

The commander of the Song forces in the castle was Wang Jian. Möngke sent his general Wang Dechen as the vanguard of the Mongol army. The Mongols initially tried to break the castle's gates. When this strategy was proven ineffective, they started night raids on the outer part of the castle on minor defensive structures. Although these raids surprised the Song army at first, the Mongols were not able to break into the castle.  

During one of these attempts in the summer of 1259, a mongol officer, Bayan, fought and killed a Chinese commander, who was an Assassin of the Chinese Brotherhood. As a result, the mentor of the Brotherhood, Kang, recruited Zhang Zhi, the Assassin's daughter, to take her father's place. Through rigorous training, Kang perfected her skills to kill the Great Khan himself. On August 11, 1259, Zhang Zhi infiltrated their encampment in the Diaoyu Mountain, Hechuan where she found and successfully assassinated Möngke Khan, plunging the Empire into division and straight into civil war between the Khan's younger siblings, Kublai and Ariq Böke, in a struggle to seize the title of Khan for themselves. Due to Zhang Zhi's deeds,the Mongol invasion was temporarily halted and the existence of the Song dynasty was prolonged.