The Crisis of the Tumu Fortress (simplified Chinese: 土木堡之变; traditional Chinese: 土木堡之變), also known as the Tumu Crisis (simplified Chinese: 土木之变; traditional Chinese: 土木之變; Mongolian: Тумугийн тулалдаан), or the Jisi Incident (simplified Chinese: 己巳之变; traditional Chinese: 己巳之變), was a frontier conflict between the Mongol Northern Yuan and the Chinese Ming dynasty. The Mongol Oirat ruler, Esen Taishi, captured the Chinese Emperor Yingzong on September 1, 1449.