Lü Meng's invasion of Jing Province

Lü Meng's invasion of Jing Province was fought between the warlords Sun Quan and Liu Bei in 219 in the late Eastern Han Dynasty. Sun Quan's forces, led by Lü Meng, invaded Liu Bei's territory of Jing Province (covering present-day Hubei and Hunan), which was defended by Guan Yu, and succeeded in annexing the entire province. The campaign occurred after the Battle of Fancheng and provided the trigger for the subsequent Battle of Xiaoting (also known as the Battle of Yiling).

Background
In 219, Guan Yu led his troops from Jing Province to attack Cao Cao's stronghold at Fancheng (present-day Fancheng District, Xiangyang, Hubei), that was defended by Cao Ren. Cao Ren was besieged at Fancheng by Guan Yu for some time. Cao Cao's adviser Sima Yi sent an emissary to see Sun Quan, requesting that Sun sent his forces to flank Guan Yu's rear in order to lift the siege on Fancheng. The Jiangnan region was to be given to Sun Quan as spoils of war.

Sun Quan sent an emissary to Guan Yu, relating his wish for a marriage to be arranged between his son and Guan Yu's daughter (possibly named Guan Yinping). Guan Yu rejected the marriage proposal and insulted the emissary, infuriating Sun Quan.

Sun Quan's forces stationed at Lukou (陸口) at the border were commanded by Lü Meng. Lü Meng claimed to be ill and was called back to the headquarters while Lu Xun was sent to replace Lü Meng as acting commander at Lukou. Lü Meng was actually feigning illness and he returned to the headquarters to discuss his plans with Sun Quan. In Luo Guanzhong's historical novel Romance of the Three Kingdoms, Lu Xun wrote a letter to Guan Yu, creating an impression that his forces were weaker than Guan Yu's, to put Guan Yu off guard. Guan Yu fell for the ruse and lowered his guard, thinking that the younger and inexperienced Lu Xun posed no threat to him.

Sun Quan's invasion force gradually increased in size after subsequent reinforcements arrived but since the army was stationed at Xunyang, behind the frontier, Guan Yu's intelligence service was unaware of that and provided no warning to him about a possible invasion by Sun Quan. At the same time, Guan Yu's troops were running low on supplies after Yu Jin's 30,000 surrendered troops joined his army. Guan Yu seized some food supplies from one of Sun Quan's storage bases near the Xiang River and his action further infuriated Sun Quan.

Capturing Jing Province
In around early December 219, Sun Quan's forces advanced west towards Jing Province. Jiang Qin was in command of a fleet that moved up the Han River to defend against any counterattack. Sun Jiao led his men to the river junction to act as a reserve army and to defend against possible intervention by Cao Cao's forces in their communication lines. Lü Meng led the main force from the base at Xunyang and moved upstream along the Yangtze River. Lü Meng's troops were hidden in barges rowed by soldiers disguised as civilians. They captured all of Guan Yu's surveillance outposts in a surprise attack before the guards could let out any warning signal. The event was known as "crossing the river in civilian clothing" (白衣渡江).

Guan Yu's main defense posts were at Gong'an and Jiangling, guarded by his subordinates Shi Ren and Mi Fang respectively. Shi Ren and Mi Fang were in charge of supplies but they did not assist Guan Yu in the Battle of Fancheng. Guan Yu was furious and replied that he would punish them according to military law once he returned. Shi Ren and Mi Fang were fearful and Mi secretly agreed to defect to Sun Quan's side. When Lü Meng's army attacked Jiangling, Mi Fang surrendered and welcomed Lü Meng's troops into the city. Shi Ren followed suit and surrendered as well, allowing Lü Meng's troops to overrun the entire Jing Province. Lu Xun's army also swiftly captured the counties of Zigui, Zhijiang and Yidao (夷道) as well.

Retreat and isolation at Maicheng
When Guan Yu learnt that Jing Province had fallen into Lü Meng's control, he ordered a retreat from Fancheng and advanced southwards to retake Jing Province. Lü Meng treated the surrendered troops and civilians of Jing Province well and allowed Guan Yu's messengers to meet their families. The morale of Guan Yu's army plummeted as his soldiers were unwilling to attack their homes and were more inclined to surrender instead when they saw that their families were well-treated. Besides, Cao Cao had already sent Xu Huang to reinforce Cao Ren. Guan Yu was unsuccessful in defeating Xu Huang's army and forced to retreat to Maicheng (麥城; also known as Mai Castle or Mai City, located southeast of present-day Dangyang, Hubei). By then, Guan Yu's army had shrunk in size from thousands until only a few hundred were left.

Within a few weeks after the start of the campaign, Guan Yu was isolated within Maicheng and surrounded by Sun Quan's forces on three sides and Cao Cao's from the north. On the west, at Zhangxiang, Guan Yu's troops deserted and surrendered. Guan Yu attempted to break out of the encirclement with his surviving men, among whom include his son Guan Ping and his Commandant Zhao Lei. They were captured in an ambush at Zhang Town (章; east of present-day Anyuan County, Hubei) by Sun Quan's generals Zhu Ran and Pan Zhang.

Aftermath
Sun Quan asked for Guan Yu's surrender but Guan refused. On the advice of his followers and for fear that Guan Yu might pose a threat to him, Sun Quan eventually ordered Guan Yu, Guan Ping and Zhao Lei to be executed in Linju (臨沮). Liao Hua surrendered to Sun Quan but later faked his own death and escaped to rejoin Liu Bei.

Two years later in 221, Liu Bei attacked Sun Quan to retake Jing Province and to avenge Guan Yu, leading to the Battle of Xiaoting (also known as the Battle of Yiling).

Sun Quan forces

 * Left Protector of the Army / General of Tiger's Might (左護軍 / 虎威將軍) Lü Meng
 * Lieutenant General / Right Division Commander (偏將軍 / 右部督) Lu Xun
 * General Who Attacks the North (征北將軍) Zhu Ran
 * Lieutenant General (偏將軍) Pan Zhang
 * Major (司馬) Ma Zhong, captured Guan Yu, Guan Ping and Zhao Lei in an ambush

Liu Bei forces

 * General of the Vanguard (前將軍) Guan Yu, captured and executed
 * Guan Ping, captured and executed
 * Zhao Lei, an area commander (都督) under Guan Yu, captured and executed
 * Liao Hua, after surrendering he escaped from Sun Quan to rejoin Liu Bei
 * Shi Ren, defended Gong'an (公安)
 * Mi Fang, defended Jiangling (江陵)
 * Assistant Officer in Headquarters Office (治中從事) Pan Jun
 * Assistant Officer in Division Office (部從事) Fan Zhou (樊伷), refused to surrender and rose in revolt, but failed and was captured and executed
 * Administrator of Yidu (宜都郡守) Fan You (樊友), escaped
 * Zhan Yan (詹晏)

Modern references
The campaign is featured as a playable stage in some installments of Koei's video game series Dynasty Warriors, in which it is known as the "Battle of Mai Castle". In some installments this battle is merged with the Battle of Fan Castle into one single stage. Some of Sun Quan's generals, such as Cheng Pu and Gan Ning, who did not participate in the battle in history, appeared in this stage.