The conquest of Wu by Jin was a military campaign launched by the Jin dynasty against the state of Wu from late 279 to mid 280 at the end of the Three Kingdoms period of China. The campaign, which started in December 279 or January 280, concluded with complete victory for the Jin dynasty on 1 May 280 when the Wu emperor Sun Hao surrendered. After the campaign, the Jin emperor Sima Yan (Emperor Wu) changed the era name of his reign from "Xianning" to "Taikang". Hence, the campaign has also been referred to as the Taikang campaign.
The campaign is significant in pre-1911 Chinese military history as it not only ended the chaos of the Three Kingdoms period and reunified China under the Jin dynasty, but was also the first successful large-scale military operation in Chinese history that involved a massive invasion force crossing the Yangtze. Among other aspects, its multi-directional approach, invasions by both land and water, and the sending of a naval fleet downstream along the Yangtze, have had strong influences on subsequent battles in Chinese military history.
Background
The Three Kingdoms
Following the end of the Eastern Han dynasty in 220, three contending states emerged in China and fought for control over the territories of the former Han Empire. Among the three, Wei was the most powerful one in terms of military prowess, economic resources, manpower and geographical size. The other two, Shu and Wu, reestablished their alliance against Wei in 223.
Rise of the Jin dynasty
From as early as 262, the Wei regent Sima Zhao had already started planning for the conquests of Wei's two rival states. He decided to attack Shu first because an invasion of Wu required costly and labour-intensive preparations such as constructing naval vessels and opening up waterways for the vessels. He also pointed out that if Wei managed to conquer Shu, they could make use of Shu's geographical advantage by sending a naval fleet downstream from Shu to attack Wu. In the winter of 262, as the Wei government mobilised troops from the various provinces for the Shu invasion, they also put Tang Zi in charge of overseeing the construction of warships in preparation for a future invasion of Wu.
In February 266, about 26 months after the surrender and end of Shu, Sima Zhao's son and successor Sima Yan usurped the throne from the last Wei emperor Cao Huan and established the Jin dynasty to replace Wei. During this time, Sima Yan heeded his advisers' suggestions to win over the Shu people's hearts by showing benevolence and generosity, as well as to induce Wu subjects to defect to Jin by tempting them with rewards and incentives. Among other things, he made the former Shu emperor Liu Shan a duke, and awarded peerages, titles and appointments to numerous former Shu subjects and their descendants, including Luo Xian, Chen Shou, Zhuge Jing, Lü Ya, Fei Gong and Chen Yu.
On 29 April 269, Sima Yan ordered Yang Hu to station at Xiangyang and supervise military affairs in the Jin-controlled territories in Jing Province.
Decline of Wu
In 264, following the Wu emperor Sun Xiu's death, his nephew Sun Hao came to the throne. In the same year, the Wei regent Sima Zhao sent two former Wu officers Xu Shao (徐紹) and Sun Yu (孫彧), who defected to Wei during the Shouchun rebellion, to deliver a letter to Sun Hao. In the letter, Sima Zhao pointed out that Wu stood no chance against a Wei invasion and told Sun Hao that he would be treated generously if he surrendered.
Around April 265, Sun Hao sent Ji Zhi (紀陟) and Hong Qiu (弘璆) as his emissaries to meet Sima Zhao, and express his desire for Wei and Wu to coexist peacefully. Ji Zhi and Hong Qiu accomplished their diplomatic mission well and even impressed Sima Zhao with their replies to questions from various Wei officials.
Sima Zhao died in September 265. In February 266, after Sima Zhao's eldest son Sima Yan usurped the Wei throne and established the Jin dynasty, Sun Hao sent Zhang Yan (張儼) and Ding Zhong (丁忠) as his representatives to attend a memorial service for Sima Zhao. After Ding Zhong returned, he advised Sun Hao to launch an attack on the Jin-controlled Yiyang Commandery (弋陽郡; around present-day Xinyang, Henan) because it was poorly guarded. When Sun Hao consulted his subjects, Lu Kai and Liu Zuan opposed and supported launching the attack respectively. Sun Hao secretly desired to heed Ding Zhong's suggestion but ultimately dropped the idea after considering the recent fall of Wu's ally state Shu.
In comparison with Wei and the subsequent Jin dynasty, Wu experienced greater problems of its own: the succession from the third Wu emperor, Sun Xiu, was marred with bloodshed and internal conflict. Sun Xiu's successor, Sun Hao, was a tyrant who made little effort to prepare for the imminent invasion by the Jin dynasty. Sun Hao's rule was more harsh as compared to the later part of the reign of Sun Quan, Wu's founding emperor. This caused a continuous wave of peasant uprisings and military mutinies, which mainly took place in present-day Zhejiang and Guangdong. Not only did Sun Hao refuse to accept advice to strengthen Wu's defences and reduce the burden on its people, he also executed around four dozen high-ranking officials who provided good counsel on governance. As a result, the Wu government had already lost the popular support of the people, and many regional commanders stationed at the border defected to the Jin dynasty.
At the same time, Sima Yan sent envoys to Wu to cease hostilities between the two states, in order to buy time for making preparations. The Wu emperor Sun Hao, in turn, viewed such actions as a sign of weakness of the Jin dynasty, and further let down his guard.
Jin preparations
Sima Yan had long harboured the ambition of conquering Wu. On 29 April 269, he designated three locations as bases for staging the invasion, and gave assignments to three generals as follows:
During his tenure in Jing Province, Yang Hu governed the region well and not only gained the locals' trust and respect, but also attracted many defectors from the Wu side. He also reduced the number of troops assigned to patrol and guard the Jin–Wu border, and reassigned them to work in agricultural colonies covering an area of over 800 qing. When he first came to Jing Province, his troops had less than 100 days' worth of food supplies. However, by the end of his third year in Jing Province, his troops had produced and stockpiled sufficient food supplies to last them for about ten years.
Construction of a navy in Yi Province
In 272, Yang Hu pointed out to Sima Yan that their forces could take advantage of their position in Yi Province and send a naval fleet downstream along the Yangtze to attack Wu. He secretly recommended to the emperor to appoint Wang Jun, who previously served as an army adviser under him, to serve as the Inspector of Yi Province (益州刺史) and oversee the construction of a naval fleet. Shortly after he was appointed as the Inspector of Yi Province, Wang Jun was also commissioned as Prancing Dragon General (龍驤將軍) and put in charge of supervising military affairs in Yi and Liang provinces.
Wang Jun reassigned his troops from farming in the agricultural colonies to start building vessels for the upcoming naval invasion of Wu. During this time, Wang Jun's assistant He Pan pointed out that they needed to recruit at least 10,000 labourers from every commandery in Yi Province for the project, which could be completed within a year. He Pan also advised Wang Jun to notify the central government after they had started the project because the central government might reject their idea of recruiting 10,000 labourers from every commandery. Wang Jun heeded He Pan's advice.
To make up for the Jin navy's lack of experience in naval warfare in comparison to the Wu navy, Wang Jun constructed many large vessels equipped with ram bows. The largest of these vessels were 120 bu long and capable of carrying up to 2,000 troops on board. These vessels also had viewing towers and three-storey-tall fortifications made of strong wood. In addition, the vessels had doors on all four sides to allow troops to board and get off easily. Horses could even run freely on board. It took Wang Jun a total of seven years to build the naval fleet and the only thing left to do was to train his troops in naval warfare.
Yang Hu's role
In November or December 276, Yang Hu wrote a memorial to Sima Yan to outline a plan for the conquest of Wu as follows: Jin forces in Yi Province to attack Wu from the west on both land and water; Jin forces in Jing Province to attack Jiangling; Jin forces in Yu Province to attack Xiakou; and Jin forces in Xu, Yang, Qing and Yan provinces to attack Moling. He explained that the idea of invading Wu from multiple directions was to confuse the Wu forces and demoralise the Wu forces by creating the impression of an overwhelming invasion. He further pointed out Wu's only strategic advantage was the Yangtze, which served as a natural barrier. However, once the Jin forces break through the Wu defences along the Yangtze, the Wu forces would retreat to behind their walled cities and fortresses. By then, the Jin forces, which were more adept in land-based warfare, would gain the upper hand over their adversaries. He also noted that Sun Hao was a highly unpopular ruler among his people and that a Jin invasion would provide a long-awaited opportunity for many Wu subjects to defect to the Jin side.
Sima Yan strongly agreed with Yang Hu's views and wanted to implement the plan. When Yang Hu's plan was put up for discussion in the Jin imperial court, many officials, including Jia Chong, Xun Xu and Feng Dan, argued that it was not time to attack Wu yet because they had to deal with the Xianbei rebels in Yong and Liang provinces. Only Du Yu and Zhang Hua supported Yang Hu's proposal.
In July or August 278, due to poor health, Yang Hu left his post at Xiangyang and moved to Luoyang to recuperate. When Sima Yan sent Zhang Hua to visit him, Yang Hu told Zhang Hua that they should seize the opportunity to conquer Wu while Sun Hao was still in power since Sun Hao's tyranny had already caused him to lose popular support from the Wu people. He also recommended Du Yu to replace him as the general overseeing military affairs in Jing Province. He died on 27 December 278.
Other preparations
In October 276, the preparation was roughly completed and Yang Hu suggested to Sima Yan to launch the attack. Yang Hu's suggestion was initially accepted but then delayed due to Jia Chong's objection, because northwestern China was still in the midst of a tribal rebellion. In July 277, additional assignments were given in order to prepare for the campaign against Eastern Wu:
After Yang Hu's death, Du Yu succeeded him and was appointed Senior General Who Conquers the South (征南大將軍) to take charge of military affairs in Jing Province from November 278.
Wu preparations
In February 270, the Wu general Ding Feng led an attack Jin's southern border at Wokou (渦口; northeast of present-day Huaiyuan County, Anhui) but was driven back by Jin forces under Qian Hong. In May of that year, following Shi Ji's death, the Wu emperor Sun Hao put his general Lu Kang in charge of military affairs in an area covering present-day Yichang and Gong'an in western and southern Hubei.
Before Lu Kang died in 274, he foresaw that Xiling (西陵; around present-day Yichang, Hubei) was a crucial location along Wu's western border so he advised Sun Hao to pay closer attention to the Wu defences in that area. After Lu Kang's death, Sun Hao split Lu Kang's command among his five sons: Lu Yan (陸晏), Lu Jing, Lu Xuan (陸玄), Lu Ji and Lu Yun (陸雲).
In the meantime, the wood shavings and other waste products from Wang Jun's naval construction project in Yi Province floated downstream along the river and entered Wu territory. The Wu officer Wu Yan, who was stationed at Jianping Commandery (建平郡; around present-day Zigui County, Hubei), picked up the wood shavings and realised that the Jin dynasty was building a naval fleet to attack Wu. He then sent the wood shavings to Sun Hao as evidence of an impending Jin invasion, and advised the emperor to send more troops to guard Jianping. When Sun Hao ignored him, Wu Yan ordered his troops to use heavy iron chains to set up a blockade along the river and prevent enemy vessels from passing through.