In 643 BCE, Duke Huan of Qi, who had dominated the Central Plains for over thirty years, passed away, and his sons attacked each other to fight for the throne, plunging the state of Qi into chaos. The three men Yi Ya, Shu Diao, and Kai Fang deposed the crown prince, Gongzi Zhao, whom Duke Huan had appointed, and installed Gongzi Wukui as ruler, while Gongzi Zhao fled to the state of Song.
During the lifetime of Duke Huan of Qi, Duke Xiang of Song actively upheld Qi's hegemony and maintained excellent relations with the Qi state. Since all of Duke Huan's sons were born to concubines and held equal status, he feared that after his death they would fight for the throne, so he entrusted his son Prince Zhao to Duke Xiang of Song. Duke Xiang of Song had always prided himself on benevolence and righteousness, and when Prince Zhao indeed came to seek refuge, he naturally felt duty-bound to take him in.
Duke Xiang of Song was the second son of Duke Huan of Song; early in his reign, he appointed the virtuous ministers Ziyu and Gongsun Gu to assist in governing, which brought great order to the state of Song. The growth of Song also ignited Duke Xiang's ambition to dominate the other feudal lords. Just then, Prince Zhao of Qi sought refuge with him, and Duke Xiang saw an opportunity to use the mission of suppressing the rebellion in Qi to inherit Duke Huan of Qi's hegemonic legacy and seize Qi's position as the leader of the alliance.
Therefore, Duke Xiang of Song notified the various states that he would escort Prince Zhao back to Qi to become its ruler, but in the end, only a few small states like Wei, Cao, and Zhu sent some troops. Duke Xiang of Song then led this four-state allied army to attack Qi. The Qi nobility, who had always favored Prince Zhao, now with the support of Song's military, united to kill Wukui and Shudiao, drive away Yiya, and welcome Prince Zhao back to ascend the throne as Duke Xiao of Qi.
Duke Xiang of Song believed that by quelling the chaos in the State of Qi and installing Duke Xiao of Qi on the throne, the other feudal lords would view the State of Song with newfound respect, so he sought to strike while the iron was hot by convening a meeting of the feudal lords to secure his position as the leader of the alliance.
At this time, Duke Xiang of Song already considered himself the hegemon. When the state of Teng (present-day Tengzhou, Shandong) refused to submit to Song, Duke Xiang detained Duke Xuan of Teng. Next, he invited the states of Cao, Zhu, and Zeng to a meeting at Caonan; when the ruler of Zeng arrived late, he ordered Duke Wen of Zhu to take the ruler of Zeng as a sacrificial offering. In autumn, because Cao did not send him a sheep, he took this as a sign of disrespect and sent troops to besiege Cao. Duke Xiang's arrogance angered the other feudal lords, and Duke Mu of Chen proposed restoring the good relations of Duke Huan of Qi, uniting the states of Lu, Cai, Chu, Zheng, and Qi in an alliance at Qi—ostensibly to commemorate Duke Huan of Qi, but in reality to oppose Duke Xiang of Song. Thus, two major camps formed among the feudal lords: one led by Chu, Qi, Zheng, Chen, and Cai, and the other by Song, which sought hegemony, along with its allied small states of Wei, Zhu, Cao, and Hua.
Duke Xiang of Song, seeing that he could not command the respect of the other feudal lords, decided to first secure the support of the two major states of Chu and Qi in order to pressure the other lords into submission. He therefore sent envoys to Chu and Qi to discuss the matter of convening an alliance of the feudal lords. King Cheng of Chu secretly mocked Duke Xiang for overestimating his own abilities and initially had no intention of responding. However, his senior minister Dechen advised that this could be an opportunity to advance into the Central Plains and contend for the position of alliance leader, so King Cheng of Chu agreed to attend the meeting on time.
In 639 BCE, Duke Xiang of Song brought Duke Xiao of Qi together with the ruler of the state of Chu at Ludi in Qi to discuss convening an alliance of the feudal lords. Believing that his position as leader of the alliance had been affirmed by Qi and Chu, Duke Xiang of Song assumed an air of superiority, acting as the de facto leader and unilaterally drafting a proclamation stating that Song would host a meeting of the lords to jointly support the Zhou king, scheduling the covenant for autumn at Yudi (present-day Sui County, Henan). Although King Cheng of Chu and Duke Xiao of Qi were displeased with Duke Xiang's actions, they agreed to the proclamation's terms out of courtesy.
In autumn, when going to the meeting at the place of Yu before the alliance, Duke Xiang of Song's younger brother, Prince Yimu, felt that King Cheng of Chu's intentions were unpredictable and worried that Duke Xiang might be deceived, so he advised him to bring troops. However, Duke Xiang of Song said that he had already agreed with Chu not to bring troops and could not break his promise. He believed that if he treated Chu with sincerity, Chu would not deceive him, and he insisted on going without troops. Yimu had to suggest that Duke Xiang keep his word and go lightly, while he himself would lead a contingent of soldiers to ambush three li away to guard against unforeseen events. But Duke Xiang of Song scolded him, saying that doing so would also be a breach of faith. To prevent Yimu from setting an ambush and undermining his integrity, Duke Xiang insisted that Yimu accompany him to the meeting.
When they arrived at Mengdi, the rulers of six states—Chu, Chen, Cai, Xu, Cao, and Zheng—all came, but only Duke Xiao of Qi and the ruler of Lu were absent. King Cheng of Chu sought to claim the position of alliance leader, which greatly angered Duke Xiang of Song, who refused to yield. At the king's command, the five hundred attendants who had come for the meeting shed their outer garments, revealing armor and swords. These armed soldiers quickly seized control of the assembly grounds, and the terrified feudal lords dared not utter a sound. King Cheng of Chu then ordered his troops to arrest Duke Xiang of Song and, directing the already prepared Chu army, launched an attack on the state of Song.
Mu Yi took advantage of the chaos to flee back to the Song state, where he united the Song people in steadfastly defending their city, stubbornly resisting the Chu army and refusing to surrender, ultimately thwarting King Cheng of Chu's scheme to destroy Song. King Cheng of Chu took Duke Xiang of Song back to Chu, intending to use him as leverage against Song. Gongsun Gu, a high-ranking official of Song, deliberately spread word that Mu Yi had ascended the throne as the ruler of Song, rendering Duke Xiang of Song useless to Chu. Later, with mediation from the states of Qi and Lu, King Cheng of Chu finally released Duke Xiang of Song back to his state. Upon Duke Xiang's return to Song, Mu Yi immediately abdicated, allowing Duke Xiang to reclaim the throne.
As a result, Duke Xiang of Song harbored a grudge against the state of Chu, but since Chu was powerful and strong, there was nothing he could do about it. At that time, the state of Zheng was small and weak, acting like a weather vane that leaned toward whichever major power was stronger. Seeing that Chu was flourishing, Zheng began to align itself with Chu. Soon after, Duke Wen of Zheng went to Chu to pay a visit to King Cheng of Chu. Duke Xiang of Song saw this as an opportunity to attack Zheng and vent his pent-up anger.
In 638 BCE, an enraged Duke Xiang of Song, ignoring the objections of Prince Muyi and Grand Marshal Gongsun Gu, allied with the small states of Wei, Xu, and Teng to launch an attack on Zheng. Duke Wen of Zheng sought help from Chu, which naturally sent troops to rescue him, but instead of directly aiding Zheng against Song's forces, the Chu army struck at Song's defenseless homeland. Unable to manage both fronts, Duke Xiang of Song had to lead his troops back in a frantic night march. The Song and Chu armies faced off on opposite banks of the Hong River (north of present-day Zhecheng, Henan). The disparity in strength between the two sides was vast, but Duke Xiang, burning with a desire for revenge, prepared to engage Chu in battle. Gongsun Gu advised Duke Xiang that Song's forces were too weak to withstand Chu's powerful army, noting that Chu's campaign was solely to rescue Zheng, and since Zheng was now relieved, their objective was achieved, urging a peace settlement. Duke Xiang, however, insisted that no matter how strong Chu's army was, it was an unjust force, while Song's army, however weak, was a righteous one, and that injustice could never overcome righteousness. Thus, Duke Xiang of Song stubbornly resolved to fight Chu to the finish, even having a large banner embroidered with the words "Righteousness and Benevolence" made, intending to use these virtues to defeat the formidable Chu.
After daybreak, the Chu army began crossing the river. Gongsun Gu proposed a plan, saying that if they attacked while the Chu army was halfway across, they would catch them off guard and surely win. However, Duke Xiang of Song pointed to his banner of "benevolence and righteousness" and said that attacking someone while they were in the middle of crossing a river was taking advantage of their predicament and went against the principles of benevolence and righteousness, so he disagreed.
The Chu army had all crossed the river and were hastily forming their battle lines on the bank. Gongsun Gu again advised, saying, "If we attack now while the Chu troops have just crossed and are not yet firmly positioned, we still have a chance to win." Duke Xiang of Song angrily replied, "How can we attack before they have even set their formation? That would betray the name of a righteous army!" Thus, he missed another opportunity.
The Chu army had already formed their battle lines and charged forward in formation, only then did Duke Xiang of Song order his troops to attack. As a result, the Song army fell into chaos, Duke Xiang himself was trapped among the enemy ranks and struck by an arrow in the thigh, while all his personal guards were killed. Only through the desperate protection of his subordinates did Duke Xiang manage to escape and return to the state of Song. The banner of "righteousness" that the Song state had raised was already trampled and torn to shreds on the battlefield.
After the defeat at the Battle of Hongshui, the common people cursed Duke Xiang of Song for his incompetence, yet he still believed he had done nothing wrong by adhering to benevolence and righteousness in the war. Later, his arrow wound reopened, and he died shortly thereafter.
Duke Xiang of Song failed to adapt to changing times, stubbornly clinging to ancient principles of warfare, which led to his defeat and heavy losses. He never truly became a hegemon in his lifetime and died with deep regret, making his quest for dominance a historical laughingstock.