The ambitious Sima Zhao killed Emperor Cao Mao of Wei and then conquered the Shu kingdom, growing ever more powerful, but before he could destroy the Wu kingdom, he fell ill and died; his son Sima Yan succeeded him as the Prince of Jin. Sima Yan was even more ruthless than his father—within months of becoming Prince of Jin, he deposed Emperor Cao Huan of Wei and made himself emperor, thus bringing the Wei kingdom to an end.
In 265 AD, Sima Yan proclaimed himself emperor in Luoyang, establishing the Jin Dynasty, historically known as the Western Jin. After ascending the throne, Sima Yan posthumously honored his father, Sima Zhao, as Emperor Wen with the temple name Taizu; posthumously honored his uncle, Sima Shi, as Emperor Jing with the temple name Shizong; and posthumously honored his grandfather, Sima Yi, as Emperor Xuan with the temple name Gaozu.
At this time, the emperor of the Wu Kingdom was Sun Hao, the grandson of Sun Quan. Sun Hao was cruel and arrogant; not only did he lead a lavish and corrupt personal life—building grand palaces and indulging in sensual pleasures—but he also enacted a series of harsh and brutal punishments to oppress the common people. Although the officials and the populace hated him in their hearts, none dared to speak out. Under Sun Hao's reckless extravagance, the Wu Kingdom's national strength gradually declined.
After Sima Yan ascended the throne, his first priority was to destroy the Wu Kingdom. Seeing that the Wu emperor Sun Hao had thrown the country into chaos, with the people voicing grievances everywhere, Sima Yan and his ministers all believed the time was ripe to attack Wu, so they dispatched troops southward.
In 279 AD, Emperor Wu of Jin, Sima Yan, ordered the Grand General of the Southern Pacification, Du Yu, the General of the Eastern Pacification, Wang Hun, and the Inspector of Yizhou, Wang Jun, to each lead large armies in a three-pronged attack on the Wu capital of Jianye (present-day Nanjing, Jiangsu). Du Yu was responsible for the central front, first attacking Jiangling; Wang Hun handled the eastern front, approaching Wu from the Hengjiang region (present-day Dangtu, Anhui); while Wang Jun advanced by water, sailing east along the Yangtze River to strike Wu.
Wang Jun was a highly intelligent man. Before the order was given to conquer the Wu Kingdom, he anticipated that Sima Yan would soon launch an attack on Wu, so he had ships built in Yizhou to launch a waterborne assault. He instructed the shipbuilders to construct vessels larger than any before, each capable of carrying over two thousand men, complete with walls and watchtowers on deck, almost identical to land-based fortifications. Sentries could observe the surroundings from the towers, and soldiers could fight on the walls. Because of this advantage, Wang Jun's warships were also known as "tower ships."
Of course, the shipbuilding activities could not be allowed to be known by the state of Wu, but as the shipwrights cut and shaped the timber, inevitably some small wood chips and fragments fell into the river. These pieces drifted downstream into the territory of Eastern Wu, catching the attention of a man named Wu Yan, who was the governor of a commandery in Wu. He noticed that for some time, wood chips had been floating down from upstream, and his intuition told him that something significant was happening upriver. Considering that Shu Han had already been conquered and Sima Yan had declared himself emperor, establishing the Jin state, Wu was in a precarious position. Wu Yan concluded that Jin was secretly building a fleet to prepare for an attack on Wu.
Wu Yan urgently reported this matter to Sun Hao, but Sun Hao paid no attention at all and instead scolded Wu Yan for making a fuss and being afraid of death. He said, "What is there to fear from the Jin Kingdom? They should be guarding against me not attacking them—how could they possibly invade Wu!" Wu Yan disagreed with Sun Hao's view in his heart but dared not argue. Since the emperor would not take action, he decided to strengthen defenses himself. Wu Yan ordered his men to drive many thick wooden stakes into the river at strategically dangerous points, then linked them together with iron chains, blocking ships from traveling on the river. He also placed many iron spikes over ten feet tall at the riverbed, so that when ships passed over them, they would be punctured with holes. After all these defenses were set up, Wu Yan's anxious heart finally settled.
After several months of fierce fighting, Du Yu and Wang Hun successfully captured the towns along their respective fronts, but only Wang Jun's fleet, advancing by water, was stalled at Zigui and unable to move forward. With the Wu border just ahead, the iron chains and iron spikes in the river made his towering warships unable to advance an inch. After racking his brains for several days, Wang Jun finally came up with a brilliant solution.
Wang Jun ordered his soldiers to build many large wooden rafts, placing scarecrows on them dressed in armor and holding weapons such as swords and spears. He then had soldiers skilled in swimming tow these rafts downstream. As the rafts passed over the iron spikes, the spikes pierced through the rafts but became stuck in the wood, and as the rafts continued downstream, the spikes were carried away. Next came the iron chains suspended between wooden stakes, which could not be removed or pulled out easily. Wang Jun thought it over and decided to use fire. He ordered large torches filled with hemp oil to be set up on the rafts, which were then towed next to the stakes. The flames ignited both the stakes and the chains, and once the stakes were burned through and the chains snapped, the ships could pass through smoothly.
After Du Yu's army had captured Jiangling, the soldiers were all exhilarated and their morale was extremely high. At this moment, someone in the army suggested taking a break to rest before launching the next attack. Du Yu said, "Now that the soldiers' fighting spirit is soaring, we should press on in one go straight to Jianye. It's like splitting bamboo—once you've cracked open the first few joints, the rest of the bamboo will naturally split apart with just a gentle push." Following this, Du Yu joined forces with Wang Jun's navy and charged toward Jianye together.
On the eastern front, Wang Hun also advanced smoothly to Jianye, and the three armies gathered to launch a fierce attack on the Wu Kingdom. Sun Hao never expected the Jin forces to truly invade his own territory; sadly, he had made no preparations at all. In a panic, he hastily appointed Prime Minister Zhang Ti to lead a defense against Wang Jun at the river. Zhang Ti arrived at the riverbank with 30,000 troops, only to see the Jin navy's banners blotting out the sky, flapping loudly in the wind. Looking at the imposing morale of the Jin soldiers, the Wu army was already terrified. After just a few exchanges in battle, Zhang Ti slunk back with his defeated and scattered troops.
Wang Jun's navy continued to approach Jianye City, and the panicked Sun Hao sent General Zhang Xiang to resist. However, when Zhang Xiang's ten thousand soldiers saw the imposing Jin army, they lost all will to fight, and before the Jin forces even engaged, the Wu troops surrendered. Sun Hao was at a loss, but then another general named Tao Jun stepped forward, claiming he could repel the enemy. He asked Sun Hao to give him twenty thousand naval troops, boasting that he would crush the Jin army and mocking the Jin navy's small ships and incompetent sailors. This sparked a glimmer of hope in Sun Hao, who granted Tao Jun the best and largest warships of Wu and handed him the command. Tao Jun then set off eagerly.
However, the naval soldiers of the Wu Kingdom were unwilling to sacrifice their lives for a cruel ruler who took pleasure in oppressing the people. Upon learning that Tao Jun was about to set out to confront the Jin army, they fled from the military camp one by one. Tao Jun, too, dared not return to report to Sun Hao and simply escaped from Jianye as well.
Wang Jun's naval forces successfully entered Jianye, with warships covering the river near the city. Soldiers poured into Jianye, and in an instant, drumbeats thundered like rolling thunder as cheers from the Jin army echoed everywhere. Sun Hao, realizing he had no chance to resist, ordered his ministers to bind his hands behind his back and led them out of the imperial palace to surrender to Wang Jun.
At this point, the Three Kingdoms period officially ended, and the Jin Dynasty established by the Sima clan unified the country.