As a result of trade sanctions issued by the
Ming dynasty,
Esen Taishi, leader of the
Oirat Mongols, led an invasion against the Ming dynasty in the year 1449. In September, Esen was victorious in the
Tumu Crisis, resulting in
the Zhengtong Emperor being captured. Esen attempted to use the captured Zhengtong Emperor to raise a ransom and negotiate a favorable treaty including trade benefits. The emperor's family planned to raise funds to secure the emperor's release. The Ming court at first was inclined to follow the counsel of Xu Youzhen, an official who suggested that since the garrison forces around Beijing were less than 100,000, the court should retreat to
Nanjing while things were still in balance. This was following the example of when the
Song dynasty moved to
Hangzhou after the Jurchen
Jin dynasty captured its capital of Kaifeng. However the
Minister of War,
Yu Qian rejected this proposal and said those who advocated retreat should be executed. On 22 September,
Zhu Qiyu, the younger brother of the Zhengtong Emperor became the new emperor of the Ming dynasty. Orders claiming to be issued by the previous emperor were to be ignored and no negotiations regarding the hostage situation would be entertained. The rationale was that the emperor's life is not as important as the fate of the country. Yu Qian was promoted to minister of war although he had been already planning and arranging measures for the defense of Beijing beforehand. Yu Qian believed that a major reason for the defeat in the Tumu Crisis was poor logistics and lack of supplies. Large granaries were set up and the logistic network was reworked. Reserve forces from neighboring provinces such as
Shanxi,
Shandong and
Henan were mobilized to defend the capital and weapon manufacturing was significantly increased. By the time of the battle, Beijing had a force of around 220,000 soldiers ready. As a result of the Ming dynasty installing a new emperor, Esen was unable to leverage the Zhengtong Emperor to obtain a deal. Therefore, his chieftains agreed to move forward to invading Beijing with the claim of wanting to restore the Zhengtong Emperor to power. ==Battle==