He was killed in action on the same day he was crowned emperor, when Caizhou fell to the allied forces of the Mongol Empire and Southern Song dynasty.
Upon arriving in Caizhou, Wanyan Chenglin advised Emperor Aizong to establish a central command and actively prepare defences for an attack by the Mongols.
Wanyan Chenglin refused to accept, but the emperor insisted and said, "I am fat and unable to ride on horseback into battle.
On 9 February 1234, shortly after the abdication ceremony started, they received news that the enemy had breached the city walls.
Wanyan Chenglin, on the other hand, rallied his soldiers and engaged the enemy in battle in the streets and alleys.