Pei Ji (570 – 629[1]), courtesy name Xuanzhen, formally Duke of Hedong, was an important official and one-time chancellor[2] of the Tang dynasty.
Pei Ji was from Pu Province (蒲州, roughly modern Yuncheng, Shanxi), under Northern Zhou rule during the time of his birth.
During the reign of Emperor Wen of Sui, he became an officer in the guard corps, but was said to be so poor that, in order to report to the capital Chang'an for duty, he had to walk there.
He also allowed Li Yuan to, against strict laws, have sexual relations with some of the ladies in waiting at Jinyang Palace, assumed by some historians as the main reason to rebel against Sui dynasty due to fear of severe punishment from the Emperor.
Once he did, Pei, who had considerably personal wealth and further had control of the storage facility, offered a large supply of rice, silk, and armor, as well as 500 ladies in waiting, to Li Yuan.
Instead, per Pei's suggestions, after Li Yuan subsequently defeated Sui forces at Huoyi (霍邑, also in modern Yuncheng), he left part of his army to siege Hedong, while himself crossing the Yellow River into Guanzhong (i.e., the Chang'an region).
In 618, Emperor Yang was killed in a coup at Jiangdu (江都, in modern Yangzhou, Jiangsu) led by the general Yuwen Huaji.
In 619, Liu Wuzhou captured Taiyuan, forcing Emperor Gaozu's son Li Yuanji the Prince of Qi to flee.
Meanwhile, Emperor Gaozu summoned Pei back to Chang'an and put him under arrest briefly, but soon released him and continued to honor him.
During the years, Pei offered several times to retire, and in 626, Emperor Gaozu granted him the honorific title of Sikong (司空) and allowed him to effectively retire, but further continued to set up rotations of junior officials from the executive bureau who would attend to Pei on a daily basis.
Although Pei Ji appeared to have supported Li Jiancheng in the struggle, Emperor Taizong initially continued to honor him, and on one occasion, when Emperor Taizong was offering sacrifices to heaven outside the capital, he requested Pei and Zhangsun Wuji to ride with him in the imperial wagon, a great honor at the time.
Subsequently, the head servant embezzled money from Pei and feared punishment, and therefore reported the incident to Emperor Taizong.