Mongol–Jin War: The Mongols entered and began looting Kaifeng, the capital of the Jin dynasty of China, after a 13-month siege. Mongol conquest of the Jin dynasty: The Mongol conquest of the Jin dynasty, also known as the Mongol–Jin War, was fought between the Mongol Empire and the Jurchen-led Jin dynasty in Manchuria and North China. The war, which started in 1211, lasted over 23 years and ended with the complete conquest of the Jin dynasty by the Mongols in 1234. May 29, 1233. Wiki link