Tumu Crisis

The Tumu Crisis (simplified Chinese: 土木之变; traditional Chinese: 土木之變; Mongolian: Тумугийн тулалдаан); also called the Crisis of Tumu Fortress (simplified Chinese: 土木堡之变; traditional Chinese: 土木堡之變) or Battle of Tumu (Chinese: 土木之役), was a frontier conflict between the Oirat Mongols and the Chinese Ming dynasty which led to the capture of the Zhengtong Emperor on September 1, 1449, and the defeat of an army of 500,000 men by a much smaller force.

• http://en.wikipedia.org/wiki/Tumu Crisis