At the beginning of the Zhou Dynasty, King Wu died of illness, and his successor King Cheng was still relatively young. Thus, the Duke of Zhou assisted in handling political affairs, which contributed to the turbulent political nature of the dynasty. In this context, Guan Shu (the first and only ruler of Guan, a vassal state of the Zhou Dynasty), Cai Shu (the first ruler of Cai, a vassal state of the Zhou Dynasty) and Wu Geng (the son of Zhou, the last king of the Shang Dynasty), who were enfeoffed with the former lands of the Shang Dynasty, rose in rebellion against the Duke of Zhou, which became known as the “Rebellion of the Three Guards.” The rebellion saw the collusion between the forces of the former dynasty and the internal forces of the new dynasty, and was supported by small eastern states such as the State of Xu and the State of Yan. Putting down the rebellion became an important issue for guaranteeing the stability of the kingdom in the early Western Zhou Dynasty.
The inscriptions on the “Qin” Bronze Gui record the important historical event that saw the Duke of Zhou launch the “Eastward Expedition” to put down the rebellion and destroy the State of Yan, making them precious historical materials. The inscriptions mention many prominent historical figures, such as King Cheng of Zhou, the Duke of Zhou, and Boqin (the eldest son of the Duke of Zhou, who was granted the newly established State of Lu instead of his father and was the founder of the State of Lu during the early Zhou Dynasty). Their titles and their roles in this expedition provide important clues for explaining unresolved issues from the early Western Zhou Dynasty, such as the Duke of Zhou taking over the regency of the young King Cheng and Boqin being enfeoffed with the State of Lu instead of the Duke of Zhou.