Zhengtong Emperor
The Oirat Mongol leader Esen Tayisi launched an invasion into Ming China in July 1449. The chief eunuch Wang Zhen encouraged the Zhengtong Emperor (r. 1435–1449) to personally lead a force to face the Mongols after a recent Ming defeat; marching off with 50,000 troops, the emperor left the capital and put his half-brother Zhu Qiyu in charge of affairs as temporary regent. In the battle that ensued, his force of 50,000 troops were decimated by Esen's army. On 3 September 1449, the Zhengtong Emperor was captured and held in captivity by the Mongols—an event known as the Tumu Crisis. After the Zhengtong Emperor's capture, Esen's forces plundered their way across the countryside and all the way to the suburbs of Beijing. Following this was another plundering of the Beijing suburbs in November of that year by local bandits and Ming dynasty soldiers of Mongol descent who dressed as invading Mongols. Many Han Chinese also took to brigandage soon after the Tumu incident.