Emperor Aizong of Jin

Ningjiasu was the third son of Emperor Xuanzong. His mother was Emperor Xuanzong's concubine, Lady Wang (王氏), who was posthumously honored as "Empress Minghui" (明惠皇后). After Emperor Xuanzong ascended the throne, he gave the title "Prince of Sui" (遂王) to Ningjiasu. Emperor Xuanzong's eldest son and heir apparent, Wanyan Shouzhong (完顏守忠), as well as Wanyan Shouzhong's son, both died prematurely, so in 1216 Emperor Xuanzong declared Ningjiasu, his next oldest surviving son, as his heir apparent. Ningjiasu chose for himself the sinicized name "Shouxu" (守緒).

When Emperor Xuanzong died in January 1224, Wanyan Shouxu inherited the throne and became historically known as Emperor Aizong.

In 1224, he instated his consort Lady Tushan (徒單氏) as his empress consort. During his reign, Emperor Aizong tried to revive the Jin dynasty, which was on the verge of collapse due to his predecessors' policies. He ended the wars against the Southern Song dynasty, canceled the Treaty of Shaoxing free of obligation, reconciled with the Jin dynasty's former ally Western Xia, instituted internal reforms in his administration, eliminated corrupt and incompetent officials, and promoted military generals who resisted the Mongol invasion and recovered lost territories from the Mongols. However, the Mongol Empire had become a formidable power by then, and in 1227 it completely conquered Western Xia and concentrated its attacks on the Jin dynasty.

In 1232, the Mongols inflicted a crushing defeat on Jin forces at the Battle of Sanfengshan (三峯山之戰) and destroyed the bulk of the Jin armed forces. They pressed on and besieged the Jin capital, Bianjing (汴京; present-day Kaifeng, Henan Province). The defending Jin forces put up fierce resistance. At the same time, a plague hit Bianjing; around every 50 days, over 900,000 dead bodies had to be transported out of the city, excluding the dead bodies of those who were too poor to be given a proper burial.

Towards the end of 1232, Emperor Aizong fled from Bianjing, crossed the Yellow River, and sought shelter in Guide (歸德; present-day Shangqiu, Henan Province), before settling down in Caizhou (蔡州; present-day Runan County, Henan Province). The Han Chinese general Shi Tianze led troops to pursue Emperor Aizong as he retreated and destroyed an 80,000-strong Jin army led by Wanyan Chengyi (完顏承裔) at Pucheng (蒲城). In the eighth month of 1233, the Mongols asked their ally, the Southern Song dynasty, to attack the Jin dynasty at Tangzhou (唐州; present-day Tanghe County, Henan Province). Emperor Aizong sought to make peace with the Southern Song dynasty, so he sent an emissary to warn them that if the Mongols conquered the Jin dynasty, they would attack Southern Song next. The Southern Song dynasty ignored the warning.

On 9 February 1234, the allied forces of the Mongols and Southern Song dynasty besieged Caizhou and conquered the city.

• Toqto'a (c. 1345). "Volumes 17–18: Biography of Emperor Aizong". History of Jin. China.