In 579 BCE, the states of Chu and Jin formed an alliance at the western gate of Song, agreeing to temporarily cease hostilities and halt warfare. Jin, under attack from Qin and the Bai Di tribes, was eager to compromise with Chu to concentrate its forces against the Di and Qin; meanwhile, Chu, plagued by internal strife, lacked the strength to contend for hegemony with Jin. Thus, this alliance was merely a expedient measure between Jin and Chu, not a genuine reconciliation. After the Western Gate Alliance, Jin successively defeated the Di tribes and Qin, leaving Qin temporarily unable to turn eastward. Subsequently, the alliance between Qi and Jin was strengthened; the smaller states in the Central Plains all submitted to Jin, and the southern state of Wu joined forces with Jin to jointly resist Chu. Jin gained a clear advantage in the struggle for hegemony. Chu, adhering to the alliance while Jin attacked Qin, failed to send troops to aid Qin, which further bolstered Jin's power and left Chu in a passive position.
In 577 BCE, the State of Zheng, relying on the backing of the powerful State of Jin, launched an attack on the State of Xu but was defeated. Duke Cheng of Zheng, unwilling to accept this defeat, personally led another campaign against Xu, breached the outer city of its capital, and forced Xu to cede the fief of Shushen to Zheng in exchange for peace. Xu was an ally of the State of Chu, and Chu could not tolerate Zheng bullying Xu in this manner. Consequently, Chu decided to attack Zheng, indirectly contending with Jin for hegemony.
In 575 BCE, the State of Chu promised to cede the Ruyin fields to the State of Zheng as a gesture of peace, leading Zheng to betray the State of Jin and align with Chu. Zheng's Zihan led an attack on the State of Song but was defeated at Zhuobei; Zheng then regrouped and counterattacked, defeating Song at Zhuling. Shortly after Zheng's assault on Song, Jin sent envoys to Wei, Qi, and Lu, requesting their troops to join Jin in attacking Zheng. Duke Li of Jin personally commanded the four armies, appointing Luan Shu as commander of the central army with Shi Xie as his deputy; Xi Qi as commander of the upper army with Xun Yan as his deputy; Han Jue as commander of the lower army with his deputy Xun Ying remaining to guard the state; Xi Chou as commander of the new army with Xi Zhi as his deputy.
Upon learning the news, the State of Zheng urgently sought aid from Chu. King Gong of Chu personally led the campaign, with Peng Ming driving the left chariot and Pan Dang serving as the right guard; Xu Yan drove the right chariot, with Yang Youji as the right guard. He appointed Sima Zifan to command the central army, Lingyin Zizhong to lead the left army, and Youyin Zige to command the right army. Uniting the three armies with allied tribal forces to rescue Zheng, they engaged the Jin army in battle at Yanling in Zheng territory.
After the Chu army arrived at Yanling, the forces of Jin's allies—Qi, Lu, and Wei—were still on their way to Yanling. Thus, the Chu commander decided to concentrate superior forces to strike and defeat the Jin army quickly before it could join with its allies, aiming for a swift resolution. It was the twenty-ninth day of the sixth month, a day traditionally considered inauspicious for military action, but the Chu army, taking advantage of the thick dawn fog and catching the Jin forces off guard, suddenly advanced close to the Jin camp.
The Chu army was approaching, and in front of the Jin camp lay a vast expanse of mud, making it impossible to deploy chariots for battle, while allied reinforcements had not yet arrived, placing the situation at a severe disadvantage. The commander of the central army, Luan Shu, believed that the Chu troops were rash and impatient, unable to sustain their efforts, and would surely withdraw after three days; he advocated holding their ground and then launching a surprise attack when the enemy retreated. However, the deputy commander of the new army, Xi Zhi, argued that the Chu forces were disorganized, lacked order, and had conflicts among their generals, thus recommending an immediate offensive. Duke Li of Jin found Xi Zhi's analysis very convincing and decided to abandon the strategy of holding out for reinforcements, opting instead to engage the Chu army in a decisive battle. To expand the space for troop movements, Duke Li ordered the wells within the camp to be filled, the stoves leveled, and the pathways between the ranks cleared.
Before the battle, King Gong of Chu, accompanied by Grand Steward Bozhou Li, climbed onto a lookout chariot to observe the movements of the Jin army. Bozhou Li was the son of Bo Zong, a Jin official. Bo Zong was a wise and outspoken man who disapproved of the Xi clan monopolizing military power in Jin and advised Duke Li of Jin to curb their influence. The Xi clan then had him imprisoned on charges of slandering the government and exiled Bozhou Li. Fleeing to Chu, Bozhou Li took up the post of Grand Steward. The Chu king asked him about the Jin army's maneuvers, and Bozhou Li explained each action's purpose to King Gong, pointing out the location of the Jin marquis's personal guard. However, when scouting the enemy, the Chu forces failed to discern the Jin army's battle intentions and thus made no corresponding preparations.
On the Jin side, Duke Li of Jin, accompanied by Miao Benhuang, climbed a height to survey the Chu army's situation. Miao Benhuang was the son of Dou Jiao, a powerful minister of Chu; when King Zhuang of Chu suppressed the Ruo'ao clan rebellion, he killed Dou Jiao, and Miao Benhuang fled to Jin, where he was granted the town of Miao. Familiar with Chu's internal affairs, Miao Benhuang believed that the Chu army's elite forces were the royal troops in the center, which were strong, while the left and right armies consisted of Zheng troops and barbarian soldiers respectively, with low morale and disorderly ranks. He thus advised Duke Li of Jin to change the Jin army's formation, creating the illusion of a weak center to lure the Chu left and right armies into attacking the center, and once the Chu forces were encircled, to concentrate the elite troops of the upper and lower armies, together with the center, to annihilate them. Duke Li of Jin gladly adopted this plan, formulated a battle strategy based on it, and then ordered a change in the existing formation, having the center army's commander and deputy commander each lead elite units to reinforce the left and right flanks.
After the deployment was complete, the Jin army charged out of their camp and launched an attack on the Chu army from both sides of the swamp in front of their stronghold. King Gong of Chu indeed fell into the trap, believing that the Jin central army was weak, so he led his own central forces to attack, but the Jin troops put up a stubborn resistance. The Jin general Wei Qi shot King Gong of Chu in the eye, and King Gong gave Yang Youji two arrows, ordering him to shoot Wei Qi. Yang Youji hit Wei Qi with one arrow, killing him instantly. Yang Youji then returned to report to King Gong with the remaining arrow. Although King Gong of Chu had been wounded in the eye, he endured the pain and continued to command the battle from the front lines.
The fierce battle raged from morning until dusk, with neither side able to gain the upper hand. The state of Chu suffered heavy losses, and King Gong of Chu decided to temporarily withdraw his troops, allowing the soldiers to rest before resuming the fight the next day. The Chu general Zifan inspected the army, comforted the wounded, and reorganized the forces, preparing to re-engage in battle the following day.
On the Jin side, Miao Benhuang announced to the entire army to prepare for battle the next day, while deliberately allowing Chu prisoners to escape. After fleeing back to the Chu camp, they reported to King Gong of Chu that the Jin army was ready for battle. Upon hearing this, King Gong immediately summoned the commander-in-chief Zi Fan to discuss how to respond. Unexpectedly, Zi Fan was drunk that night and unable to discuss military strategy. King Gong, unsure of what to do, ultimately decided to lead the army in a night retreat. In this battle, although the Chu army suffered setbacks, the outcome between Jin and Chu was still undecided. Yet the commander-in-chief of the central army, Sima Zi Fan, was drunk on the battlefield, causing a delay in military operations and forcing the Chu king to withdraw. When the Chu army retreated to Xia, Zi Fan, under pressure from Zi Zhong, committed suicide out of fear of punishment.
The Battle of Yanling was the third hegemonic war between Jin and Chu, following the Battles of Chengpu and Bi, and also the last major confrontation between their main forces, ending with King Gong of Chu quietly withdrawing his troops. This battle weakened Chu's hegemony, marking the decline of Chu's struggle for control over the Central Plains. Although Jin consolidated its dominance through this victory, by the end of the battle, neither Lu nor Wei had sent a single soldier; only Qi dispatched reinforcements, which arrived only after Jin's forces had finished fighting and were returning home, revealing that Jin's control over the Central Plains feudal lords had already diminished.