居庸关
In the immediate aftermath of the disaster, the most pressing political concern caused by the capture of the emperor was resolved when the acting Minister of War Yu Qian (the actual minister having died at Tumu) installed the Emperor's brother as the new Jingtai Emperor (r.14501459). Military tensions with the Oirats remained high during Jingtai's reign, as peace would have caused a great deal of political awkwardness for Jingtai and Yu Qian's faction, who benefited from putting Jingtai on the throne. To maintain a military presence while compensating for the loss of soldiers, fortifications, ditches, and ramparts were constructed in key passes, including at Zijing Pass (紫荊關; through where the Mongols had entered during the Tumu Crisis), Ningwu Pass (寧武關), and Juyong Pass. The work undertaken in this period marked a major shift toward defensive construction.