Tong Pass in the context of "Hangu Pass"

Tongguan County (alternately romanized as Tungkwan) is a county in the east of Shaanxi province, China, administered as part of the prefecture-level city of Weinan. It is named after the Tong Pass, a historical fortress located south of the confluence of the Wei and Yellow Rivers. It is the southeastern corner of the Ordos Loop, the point at which the Qin Mountains turn the Yellow River sharply eastward, forcing it into the North China Plain, and borders the provinces of Shanxi to the north and Henan to the east.

Yang Guozhong (traditional Chinese: 楊國忠; simplified Chinese: 杨国忠; pinyin: Yáng Guózhōng; Wade–Giles: Yang Kuochung) (died July 15, 756), né Yang Zhao (楊釗), was a Chinese politician who served as principal chancellor of the Tang dynasty from 752 to 756, late in the reign of Emperor Xuanzong. Known in his youth as a gambler and wastrel, Yang rose rapidly to political power after his distant cousin, Yang Yuhuan, became Emperor Xuanzong's favorite consort in 744. His familial ties and skills as a financial administrator helped him navigate the tumultuous court politics of the late 740s and early 750s to become the emperor's leading chancellor in 752. While Yang enjoyed Emperor Xuanzong's trust, his competence as chancellor was questioned and he became entangled in a fierce rivalry with an erstwhile political ally, the general and imperial favorite An Lushan. Yang was blamed for precipitating An's cataclysmic rebellion in 755. In the following year, he forced the Tang army of Geshu Han, then holding favorable defensive positions in Tong Pass, to confront the rebel army, leading to a rout of Tang forces and the fall of the imperial capital, Chang'an. Yang attempted to flee to his base in Chengdu with Emperor Xuanzong, but when the imperial party stopped at Mawei Station in modern Shaanxi, Yang and his family, including Yang Yuhuan, were massacred by imperial guard soldiers who blamed them for the chaos.