Wang Zhen talked Yingzong into leading a campaign — the emperor was captured by Mongols

In 1449, the Ming dynasty was at the height of its power — a century after its founding, wealthy, expansive, and militarily dominant. The Oirat Mongol leader Esen Taishi had raided the border, but the threat was manageable. Then the eunuch Wang Zhen, the most powerful official at court, convinced the young Emperor Yingzong to personally lead a punitive campaign. Wang Zhen had recently directed a successful campaign in Yunnan and wanted to cement his military credentials. The emperor — twenty-one years old, fond of military spectacle — agreed.

The army departed Beijing in August 1449, assembled in just two days. Modern estimates put its size at around 200,000, though the court claimed 500,000. The campaign was a logistical disaster from the start: soldiers ran out of food before reaching the Great Wall. Wang Zhen ignored advice from senior generals, changed the route to show off his hometown estates, then reversed course to avoid damaging his own crops. The delays were fatal.

On 1 September, the Ming army arrived at the Tumu Fortress, exhausted and out of water. The Mongols, with only 20,000 cavalry, surrounded the camp and blocked access to the nearest river. Wang Zhen ordered the army to advance towards water, but the movement broke formation. The Mongols attacked. The elite Ming army was annihilated in hours. Half the soldiers died. Two dukes, two marquises, five counts, and hundreds of senior officials were killed. Wang Zhen was struck down by his own officers.

Emperor Yingzong was captured and taken to Esen's camp — the first Chinese emperor taken prisoner since the Jingkang Incident 322 years earlier. The court in Beijing panicked. The Minister of War, Yu Qian, refused to surrender, installed the emperor's brother as the Jingtai Emperor, and organised a successful defence of Beijing. Esen, unable to profit from his prisoner, released Yingzong after 12.5 months. But the former emperor returned to house arrest, not the throne — a situation that sparked the 1457 coup that restored him.