The Crisis of the Tumu Fortress, also known as the Tumu Crisis, or the Jisi Incident, was a border conflict between the Oirat Mongols and the Ming dynasty. In July 1449, Esen Taishi, leader of the Oirat Mongols, launched a large-scale, three-pronged invasion of China. Despite having capable generals, Emperor Yingzong of Ming, under the influence of eunuch Wang Zhen who dominated the Ming court at the time, made the decision to personally lead his armies into battle against Esen. On 1 September, the Ming army suffered a crushing defeat at the hands of the much weaker Mongols, and the emperor was captured. This defeat was one of the biggest military failures in the Ming dynasty's three centuries of existence, and it was largely attributed to the poor leadership of the Ming army.
Esen, for his part, was not prepared for the scale of his victory or for the capture of the Ming emperor. Initially, he attempted to use the captured emperor to raise a ransom and planned to conquer the undefended Ming capital of Beijing. His plan was foiled due to the steadfast leadership of the Ming commander in the capital, Yu Qian, and the ascension of the captured emperor's brother, the Jingtai Emperor. Emperor Yingzong was eventually released in 1450, but he was placed under house arrest by his brother. Esen himself faced growing criticism for his failure to exploit his victory over the Ming and was assassinated six years after the battle in 1455.
