In Duke Huan of Qi's quest for hegemony, the Battle of Changshao was a rare setback, which made him rely more heavily on Guan Zhong and stop acting arbitrarily. Guan Zhong advised Duke Huan to send people to mine iron ore, enabling large-scale production of weapons and farm tools; to develop agriculture to enrich the state and its people; to leverage Qi's coastal location to expand the fishing and salt industries; and to implement policies that reduced burdens on all social classes. Duke Huan adopted all these suggestions. With Guan Zhong's guidance, Qi quickly became prosperous, with a well-off populace and a stable society.
As the State of Qi grew increasingly powerful, Duke Huan of Qi's ambition to command the various feudal lords also intensified. Duke Huan asked Guan Zhong, "Now that the country is prosperous and the people are strong, can we dominate the feudal lords?" Guan Zhong believed that among the feudal states, the southern State of Chu, and the western states of Qin and Jin all relied on their own strength to dominate their regions, so Qi could not yet claim supremacy over all the states and command the lords. He analyzed that since the Eastern Zhou moved its capital, although the Zhou royal house had declined, in the eyes of the feudal lords, the Son of Heaven of Zhou was still the common sovereign of all under heaven. At that time, the central states were suffering greatly from invasions by the Rong and Di tribes. Therefore, Guan Zhong proposed raising the banner of "Honor the King and Expel the Barbarians," calling on all feudal lords to respect the Zhou royal house and unite to resist the incursions of the Man and Rong tribes into the central plains, thereby using this to issue orders to the lords and establish a hegemonic position in the central plains. Duke Huan greatly admired this strategy and asked where to begin. At that time, the Son of Heaven of Zhou (King Xi of Zhou) had just ascended the throne. Guan Zhong advised Duke Huan to send an envoy to congratulate the king and report that internal turmoil had broken out in the State of Song, and the new ruler, Duke Huan of Song, had just taken the throne but his position was still unstable, so the situation in Song remained unsettled. He suggested asking the king to issue a decree recognizing Duke Huan of Song as the legitimate ruler, thereby ending the unrest in Song. Once Duke Huan of Qi obtained the king's decree, he could use the authority of the Son of Heaven to summon the feudal lords and form an alliance. Duke Huan nodded in approval and immediately sent someone to congratulate the new Son of Heaven, King Xi of Zhou.
By this time, the Zhou royal court existed in name only, as the various feudal lords were all busy expanding their own territories and had long ceased to pay homage to the Son of Heaven. When King Xi of Zhou first ascended the throne, he was naturally overjoyed that a major state like Qi even sent envoys to offer congratulations, and he readily agreed to let Duke Huan of Qi exercise the authority of the Son of Heaven on his behalf, summoning the feudal lords to recognize the legitimacy of Duke Huan of Song's rule.
In 681 BCE, Duke Huan of Qi, acting on the mandate of the Son of Heaven, summoned the various feudal lords to a covenant at Beixing in the state of Qi to confirm the status of the ruler of the Song state. At that time, Qi had little prestige among the feudal lords, so when the covenant date arrived, only the four states of Song, Chen, Zhu, and Cai heeded the summons and arrived at Beixing, while states like Lu, Wei, Zheng, and Cao adopted a wait-and-see attitude and did not attend. Duke Huan of Qi felt that too few states had come and wanted to cancel the covenant, but his advisor Guan Zhong dissuaded him, arguing that they could not afford to lose credibility with the feudal lords at their very first covenant, and that three people could already constitute a crowd—now with four states present, plus Qi itself, it was already considerable. Heeding Guan Zhong's advice, Duke Huan of Qi went to meet with the rulers of the four states. During this covenant, Duke Huan of Qi, relying on his authority as the holder of the Zhou king's mandate, was elected as the alliance leader. Finally, the five states concluded a treaty, pledging to respect the royal house, repel foreign barbarians, and assist one another.
After the Beixin Alliance, Duke Huan of Qi led his army to destroy several small states that had not attended the alliance, then used military force to force the states of Lu and Zheng to sue for peace with Qi. In 679 BC, Duke Huan of Qi convened another alliance of various states at the location of Juan, and at this meeting, Duke Huan's status as hegemon was initially recognized by the various feudal lords.
In 662 BCE, a civil disturbance broke out in the State of Lu. Duke Zhuang of Lu's wife, Ai Jiang, had an illicit affair with his younger brother, and together they murdered Duke Zhuang's son, the newly enthroned Duke Min of Lu, intending to install Qing Fu as ruler. Ai Jiang was the sister of Duke Huan of Qi, who subsequently executed her, while Qing Fu committed suicide out of fear of punishment. The newly installed Duke Xi of Lu then formed an alliance with the State of Qi at Luogu, finally stabilizing Lu. By this point, Duke Huan of Qi had become a symbol of justice, greatly enhancing his prestige among the feudal lords and further expanding and consolidating his hegemonic rule.
Just as the State of Qi was gradually establishing its hegemonic position in the Central Plains, the Di and Shanrong peoples, ethnic minorities from the remote border regions, were also growing in strength. They repeatedly launched military incursions, posing a serious threat to the stability and development of the Central Plains states.
In 663 BCE, the State of Yan sent envoys to the State of Qi pleading for help, reporting that the Shanrong tribe had led ten thousand cavalry to attack Yan, plundering large amounts of grain, livestock, and property, leaving Yan unable to resist. Duke Huan of Qi was reluctant to assist Yan, but his advisor Guan Zhong suggested that since Yan was in distress and had come seeking aid, if Qi took the lead in raising an army to attack the barbarians, it would surely establish prestige among the various states. Duke Huan found this reasoning sound, so he personally led a large army to rescue Yan.
Duke Huan of Qi led a large army to the state of Yan, but by then the Shanrong had already received word of their approach, plundered a great amount of wealth, and fled. Guan Zhong advised pursuing them northward to completely defeat the Shanrong and pacify the northern regions. Duke Huan of Qi decided to follow Guan Zhong's counsel and continued the chase. At that time, near the state of Yan, there was also the state of Wuzhong (present-day Yutian, Hebei), which likewise often suffered from Shanrong raids. So Duke Zhuang of Yan, the ruler of Yan, sent envoys to seek help from Wuzhong, thereby strengthening the army that was campaigning against the Shanrong.
Duke Huan of Qi led the allied forces of three states in a northward pursuit, charging out of Jimen Pass as the Shanrong barbarians fled in panic. Learning from captured Shanrong soldiers that their chieftain had escaped to the Guzhu state, Duke Huan followed in hot pursuit and besieged Guzhu. The Guzhu general Huang Hua beheaded the Shanrong chieftain and presented the head to the Qi army, falsely claiming that the Guzhu ruler had abandoned his state and fled into the desert, offering to guide the Qi forces in pursuit. Duke Huan believed him and led his army into the desert following Huang Hua. Taking advantage of the moment, Huang Hua slipped away unnoticed, leaving the Qi army stranded in the vast desert, completely disoriented. Looking around, all they saw was endless yellow sand—how could they find a way out? Many troops were lost. By night, fierce winds swept through the desert with bone-chilling cold, and barely surviving until dawn, they faced scorching heat and unbearable thirst. Duke Huan urgently ordered the army to find an exit, but the massive force could not locate a path. Panicked, Duke Huan sought advice from Guan Zhong. It was then that Guan Zhong suddenly recalled that old horses often know the way home, and suggested to Duke Huan: "Old horses mostly recognize the return path, and the Yan horses came from beyond the northern desert. Why not select a few old horses and let them lead? They might guide the army out of the desert." With no better option, Duke Huan followed the plan. Guan Zhong picked several old horses and let them go ahead, with the entire army following closely behind. They indeed escaped the perilous desert and returned to the original road. The idiom "an old horse knows the way" originates from this story.
After the Qi army emerged from the desert, they attacked Wudi City, which had been occupied by the ruler of the Guzhu state while the Qi and Yan forces were lured into the desert. The two armies clashed fiercely, and the ruler of Guzhu was killed in the chaos of battle.
Duke Huan of Qi decisively defeated the Mountain Rong tribes, rescuing the State of Yan from danger, and destroyed the states of Lingzhi and Guzhu before returning victorious. Duke Zhuang of Yan escorted Duke Huan of Qi all the way to the border of Qi, where Duke Huan said, "Only the Son of Heaven may be escorted beyond the borders of a state by its lords; I must not allow Yan to act without propriety." He then ceded the territory that the Duke of Yan had traversed to Yan and instructed the Duke of Yan to pay tribute to the Zhou court. When this matter spread among the feudal lords, it inspired awe and respect in all of them.
When rescuing Yan, the State of Lu had promised to send troops for support but took no action. Duke Huan of Qi, following Guan Zhong's advice, not only refrained from sending troops to punish Lu but also gave them some of the war spoils from the victory over Yan that were not found in the Central Plains. This gesture deeply moved the people of Lu and earned praise from other states.
Next, Duke Huan of Qi led his troops to help the states of Wei and Xing expel the invading Mountain Rong and Western Di tribes. He also assisted Wei in rebuilding its palaces and helped Xing restore its statehood and relocate to a new capital. These righteous acts earned Duke Huan of Qi the praise and support of the various feudal lords in the Central Plains, further elevating his prestige.
At that time, besides the Northern Rong and Western Di tribes, the southern state of Chu also posed a threat to the region. Chu had long been a powerful state in the south, situated beyond the Central Plains. The Chu people cultivated land, developed production, and gradually grew stronger, with a level of social development no lower than that of the Central Plains states, and they also had a profound influence on Chinese civilization. Due to its distance from the Central Plains, after Chu became powerful, it increasingly disregarded the Zhou royal court and harbored ambitions to expand northward. By the Spring and Autumn period, Chu even went so far as to claim the title of "king." As a result, the Central Plains feudal lords regarded Chu as a "southern barbarian" and made it a common target for attack.
Duke Huan of Qi pacified northern tribes through military campaigns like aiding Yan, then decided to attack Chu in the south.
In 656 BCE, Duke Huan of Qi led a coalition of eight states—Qi itself plus Song, Lu, Zheng, Wei, Chen, Xu, and Cao—to attack Cai, an ally of Chu. The allied forces then marched toward Chu. Upon receiving the news, King Cheng of Chu immediately mobilized his troops to prepare for battle, while sending an envoy to question Qi: given the great distance between the two states, why was Qi attacking Chu without cause? Qi accused Chu of failing to pay tribute to the Zhou king; Chu admitted its fault and promised to resume tribute payments. Qi then displayed its military might to intimidate Chu, but the Chu envoy remained resolute, warning that if war broke out, Chu would fight to the end. Duke Huan of Qi, calculating that a direct assault on Chu could lead to mutual destruction, decided to end the campaign since Chu had agreed to restore tribute. Thus, the feudal lords of the Central Plains concluded a covenant with Chu at Shaoling (northeast of present-day Yancheng, Henan), after which the allied forces withdrew. This action temporarily checked Chu's northward expansion.
Soon after, a civil conflict broke out within the Zhou royal court. King Hui of Zhou wanted to depose Crown Prince Zheng and install the son of his favored concubine as the heir. In 655 BCE, Duke Huan of Qi, together with the rulers of eight other states, held a meeting at Shouzhi. Using the pretext that the feudal lords needed to pay respects to the crown prince, he brought Prince Zheng to Shouzhi and kept him there for several months. Although King Hui was angry that Prince Zheng had disobeyed him, he feared the threat posed by the powerful state of Qi, and thus the prince's position was secured. Soon after, King Hui died, and Prince Zheng ascended the throne, becoming King Xiang of Zhou. Grateful to Duke Huan of Qi, King Xiang sent him sacrificial meat from the royal ancestral temple as a token of thanks.
Duke Huan of Qi used this opportunity to notify all feudal lords to gather at Kuiqiu in Song State to entertain the emperor's envoy.
In 651 BCE, Duke Huan of Qi held a meeting with the rulers of seven states—Lu, Song, Wei, Zheng, Xu, and Cao—at Kuiqiu. During the assembly, an envoy announced the will of the King of Zhou, stating that Duke Huan could be exempted from bowing when receiving sacrificial meat (zuo). This signified that the Zhou king had recognized Duke Huan's hegemonic status. The states once again swore an oath to coexist peacefully and assist one another, among other commitments.
The Kuiqiu Alliance was Duke Huan of Qi's ninth and final gathering of the feudal lords. Through this grand assembly, Duke Huan of Qi finally achieved his goal of uniting the lords and dominating the Central Plains. Therefore, the process of Duke Huan of Qi's rise to hegemony is historically referred to as the "Nine Gatherings of the Lords."