Battle of Tumu Fortress

The Battle of Tumu Fortress (Chinese 土木堡之變 tu3 mu4 bao3 zhi1 bian4) was frontier conflict between Mongolia and the Chinese Ming Dynasty leading to the capture of Zhengtong Emperor of China on September 8 1449 by an utterly wrong deployment.

In August (the 7th month of the Chinese lunar calendar) Esen Tayisi (也先 ye3 xian1) of the Oyirad Mongols attacked the Chinese frontier with several thousand cavalry at Datong castle (today Datong County, Shanxi Province), located north and without protection of the Great Wall of China. Aided by Jurchen and diversionary attacks, the Mongols annihilated the Chinese stationary forces.

Zhengtong Emperor favoured a eunuch Wang Zhen, who suggested that the emperor lead an ambitious expedition of five hundred thousand troops to repel the Mongols and boost morale. After Esen faked a complete withdrawal back to the Mongolian steppes the emperor and Wang Zhen ran right into an ambush by chasing the Mongolian to the west and arrived at Datong.

In the night of September 3 (Chinese lunar calendar: 8th day of the 8th month), Esen wiped out all defenses and laid siege to the Datong castle. The Chinese army managed to break the siege and were chased as they retreated to the Great Wall.

Struck by a thunderstorm and suffering a tremendous loss of morale, the Chinese army was caught on the north side of a barrack, the Tumu Fortress, in the morning of September 8 (Chinese lunar calendar: 13th day of the 8th month). Esen laid siege and overwhelmed its defenses in the late afternoon despite a final charge led by Wang Zhen two hours before. The emperor was captured and most of his accompanying bureaucrats, including Wang Zhen, were killed.