Duke of Zhou, Ji Dan, was the fourth son of King Wen of Zhou and the younger brother of King Wu of Zhou, serving as the first Duke of Zhou in Zhou Dynasty history. During King Wen's reign, he was known for his filial piety and benevolence, and after King Wu ascended the throne, he fully assisted King Wu in the campaign against King Zhou of Shang. In the war to overthrow the Shang Dynasty, he "often supported King Wu on his left and right, handling most of the affairs." In the pre-Qin period, men were referred to by their clan name rather than their surname, so although his surname was Ji and given name Dan, he was not directly called Ji Dan; historically, he is known as Duke of Zhou or Shu Dan, and because his posthumous title was Wen, he is also called Duke Wen of Zhou.
In the second year after the Zhou Dynasty overthrew the Shang Dynasty, around 1045 BCE, King Wu of Zhou passed away from illness, and his son Ji Song ascended the throne, becoming King Cheng of Zhou. When King Cheng took the throne, he was only twelve years old, a young and inexperienced child who understood nothing of state affairs. With the realm newly pacified and countless tasks awaiting attention, the political situation remained unstable, and the old nobles of the Shang Dynasty were restless and plotting. Fearing that various feudal lords might take the opportunity to rebel against Zhou, King Cheng's uncle, Ji Dan, decided to personally assume regency and govern the state, acting on behalf of King Cheng to ensure timely and effective issuance and implementation of decrees.
Through his extraordinary strategic insight and decisive style of handling affairs, the Duke of Zhou quickly stabilized the political situation of the Zhou Dynasty, allowing the people to focus wholeheartedly on production. At the same time, he strengthened the education of King Cheng, hoping that he would soon grow into a true monarch. Although the Duke of Zhou and King Cheng were uncle and nephew, King Cheng was the sovereign while the Duke of Zhou was his subject. Even when King Cheng did something wrong, it was not appropriate for the Duke of Zhou to directly reprimand or punish him. Therefore, the Duke of Zhou had his own son, Boqin, accompany King Cheng in his studies and strictly disciplined Boqin, punishing him without leniency whenever he made mistakes. Through this subtle and gradual education, King Cheng of Zhou came to understand many principles and learned much about the way of being a ruler.
All major affairs of the realm were decided by the Duke of Zhou, and even King Cheng was under his guidance. The other younger brothers of King Wu of Zhou—Guanshu, Caishu, and Huoshu—seeing that the Duke of Zhou, though not bearing the title of king, was effectively exercising royal authority, grew resentful. Guanshu, in particular, had originally hoped to inherit the throne himself, and now, witnessing Ji Dan wielding power, was deeply dissatisfied. He thus spread rumors, claiming that the Duke of Zhou was ambitious, plotting to harm King Cheng and usurp the throne.
Internal turmoil broke out in the Zhou Dynasty, giving hope to the nobles of the Shang Dynasty who harbored fantasies of restoration, the most prominent of whom was Wu Geng, the son of King Zhou of Shang. After King Wu established the Zhou Dynasty, in order to better govern the remnants of the Shang people, he enfeoffed Wu Geng as the Marquis of Yin, placing him in charge of the former Shang capital, Zhaoge, which was renamed Bin. At the same time, to keep watch over Wu Geng, the areas east, west, and north of Zhaoge were divided into the regions of Wei, Yong, and Bei, which were respectively governed by King Wu's younger brothers, Guan Shu Ji Xian, Cai Shu Ji Du, and Huo Shu Ji Chu, who jointly monitored Wu Geng. This effectively surrounded Wu Geng, a setup known as the "Three Overseers."
Wu Geng, unwilling to live under others' control and constant surveillance, eagerly hoped for internal turmoil within the Zhou Dynasty. Now that Guan Shu, Cai Shu, and Huo Shu were dissatisfied with the Duke of Zhou, Dan, he seized the opportunity to incite them to unite with various feudal lords in rebellion, hoping to restore the Shang Dynasty amid the chaos. The "Three Overseers," originally tasked with preventing Wu Geng's uprising, instead allied with him and colluded with several tribes to rebel against the Zhou Dynasty—this became known in history as the "Revolt of the Three Overseers."
At this critical juncture, after a calm analysis, the Duke of Zhou resolutely decided to launch an eastern campaign to suppress the rebellion. Before sending out the troops, he first had a sincere conversation with another younger brother of King Wu, the Duke of Shao, saying that King Wu had died young and King Cheng was still a child—if the realm were to fall into turmoil at this time, the people would suffer, and the hard-won legacy built over three generations by the Great King, King Ji, and King Wen would be lost, leaving him unable to face them after his own death. It was out of concern for the Zhou dynasty's future that he set aside personal gains and losses to manage state affairs. The Duke of Zhou's words won the Duke of Shao's trust, and the two brothers worked together to stabilize the political situation, also securing the support of the majority.
Next, the Duke of Zhou began organizing an eastern expeditionary force to suppress the rebellion. Before departing, he gathered all the ministers together for a propaganda and mobilization effort, formally assembled the army, personally took command as its leader, and led the troops eastward to confront the rebel forces.
The Zhou army marched directly toward Wugeng's territory, where the Yin forces immediately scattered and Wugeng was defeated and killed. Simultaneously, the Duke of Zhou dispatched troops to attack Guanshu's stronghold at Wei, swiftly capturing the city and eliminating his rebel forces; Guanshu, feeling unable to face his brothers and nephew, committed suicide. The Zhou army then pressed on to take Caishu's base at Yong, capturing and imprisoning him, while Huoshu was exiled to a remote region, thereby consolidating Zhou rule.
After suppressing the rebellion of Wu Geng and the "Three Overseers," the Duke of Zhou sought to expand his gains through the eastern campaign, eliminating other rebellious forces to permanently remove future threats. He thus decided to first attack the state of Yan to the east. Yan, the former capital of the Shang Dynasty, was a major power in the east and the center of the main rebel forces. Minister Xin Jiajia advised that large states were difficult to conquer, while small states were easier to take, suggesting that attacking the smaller states would leave the larger ones unable to sustain themselves. The Duke of Zhou found this reasoning sound and changed his plan, leading his army southeast to attack the Nine Yi tribes, including the small states of Xu, Xiong, and Ying, located between the Huai and Si Rivers. These small states of the Nine Yi had long fought against the Shang and possessed tenacious combat capabilities. Although they retreated step by step under the powerful assault of the Zhou army, they stubbornly resisted due to their familiarity with the local terrain. After arduous and continuous fighting, the Zhou army finally conquered all the small states of the Nine Yi.
Next, the Zhou army concentrated its forces and moved north, capturing the states neighboring Yan to its west and south. Facing a situation of isolation and weakness, the ruler of Yan was forced to surrender outside the city. Yan's surrender dealt a heavy blow to the Shang forces, and states such as Pugu (also known as Bogu or Fugu, located southeast of present-day Boxing in Shandong) subsequently surrendered as well.
The Duke of Zhou's Eastern Campaign lasted a total of three years. According to the "Shangshu · Great Commentary," the Duke of Zhou "spent the first year quelling the rebellion, the second year defeating the Yin remnants, and the third year conquering the Yan state." This shows that attacking the remaining Yin-Shang forces in the Yan state was the final battle of the Eastern Campaign.
During the eastern campaign, the Duke of Zhou captured a large number of Shang Dynasty nobles. These individuals still harbored thoughts of restoring the Shang Dynasty, so they were called the "stubborn people." The Duke of Zhou felt that the capital Haojing was located in the west, making it very inconvenient to control the vast central plains in the east. Therefore, he decided to build a new capital in the east and relocate all the "stubborn people" of the Shang Dynasty there. At the same time, he sent the Duke of Zhao to station troops and strengthen supervision over them. This became the eastern capital Luoyi (present-day Luoyang, Henan). From then on, the Zhou Dynasty had two capitals: the western one was Haojing, also called Zongzhou; the eastern one was Luoyi, also called Chengzhou.
After establishing the capital at Luoyi, the Duke of Zhou began enfeoffing his relatives and meritorious officials. He established the Wei state at the former Shang capital of Zhaoge, appointing his younger brother Kangshu as its ruler. He also founded the Song state, appointing Weizi Qi, a Shang noble who had surrendered to the Zhou, as its ruler. Meanwhile, he established the Lu state in the old territory of the Yan state, appointing his eldest son Boqin as its ruler to govern the Yin people. Before Boqin left for Lu, the Duke of Zhou told him, "In the court, my status is almost unrivaled, yet I still pause to wash my hair and spit out my food, fearing I might lose the worthy men of the realm. When you arrive in Lu, you must strive to govern diligently and not be arrogant or reckless." He established a total of 71 fiefdoms, sending 15 of King Wu's brothers and 16 meritorious officials to serve as lords in these states, creating a barrier to defend the royal house. The Duke of Zhou's eastern expedition extended Zhou influence to the shores of the Eastern Sea, which was of great significance in consolidating the rule of the Zhou dynasty.
Duke of Zhou served as regent for seven years, suppressing rebellions, establishing the eastern capital, and creating a comprehensive system of laws and institutions for the Zhou Dynasty, such as uniformly planning land within the feudal states, widely implementing the well-field system to consolidate and strengthen the dynasty's economic foundation, establishing the system of primogeniture and social hierarchy to reinforce central authority, along with the "Jifu" system, "Jueshi" system, legal codes, and ritual music system, all of which ultimately secured the stability of the Zhou Dynasty's rule.
When King Cheng of Zhou reached the age of twenty, the Duke of Zhou decided to return the reins of government to him. The "Shangshu Dazhuan" records: "The Duke of Zhou acted as regent: in the first year, he quelled chaos; in the second, he conquered the Shang remnants; in the third, he subdued the Yan tribe; in the fourth, he established feudal states and defenses; in the fifth, he built Chengzhou; in the sixth, he formulated rites and music; in the seventh, he handed power back to King Cheng." Before relinquishing authority, the Duke of Zhou composed the "Wu Yi" (Against Luxurious Ease), admonishing the young king to remember the lessons of the Shang Dynasty's fall, not to indulge in sensual pleasures, but to reflect on the "hardships of farming and harvesting," to be diligent and compassionate toward the people, and to select worthy and capable officials. Then, he "returned the government to King Cheng and took his place facing north as a subject."
The Duke of Zhou assisted King Wu in overthrowing the Shang dynasty and later helped King Cheng suppress rebellions and establish institutions, dedicating himself wholeheartedly to the founding and development of the Zhou dynasty. Even until his death, the Duke of Zhou remained utterly loyal. On his deathbed, he instructed his descendants to bury him in Luoyi, as a sign that he would never leave King Cheng even in death. After his passing, King Wen, to show his respect, had him buried beside the tomb of King Wen of Zhou.
The painstaking efforts of King Wen of Zhou, King Wu of Zhou, and the Duke of Zhou over several generations created a relatively relaxed environment for King Cheng's rule, as the Zhou Dynasty's governance grew increasingly stable and its national power became stronger. King Cheng reigned for thirty years, after which his son King Kang ascended the throne and ruled for sixteen years. During this period of over forty years, the Western Zhou Dynasty experienced a prosperous and powerful golden age, known in history as the "Reign of Cheng and Kang."