How did the Yuan dynasty conquer and reunify China?

The Yuan dynasty, led by Kublai Khan, achieved the conquest and reunification of China by systematically dismantling the Song dynasty through a combination of military strategy, the use of auxiliary forces, and political maneuvering.

While Genghis Khan initiated the conquest of northern China in 1211, it was Kublai Khan who completed the process by 1279. The Mongols employed advanced siege warfare, utilizing technical specialists and Chinese auxiliary troops to overcome Song defenses. A pivotal moment was the five-year siege of the fortress at Xiangyang (1268–1273), which opened the path to the Yangtze River.123

Kublai Khan adopted a more disciplined approach than earlier Mongol campaigns, often forbidding indiscriminate slaughter to preserve the region's resources and stability. Following the fall of the Song capital, Lin’an, in 1276, the Mongols suppressed remaining loyalist resistance, culminating in the final defeat of the Song in 1279. This victory marked the first time all of China had been reunified under a single foreign power, leading to the integration of the northern and southern economies.345