Hanzhong Campaign

The Hanzhong Campaign was a military campaign launched by the warlord Liu Bei to seize control of the commandery of Hanzhong from his rival Cao Cao. The campaign took place between 217 and 219 during the prelude to the Three Kingdoms period. Liu Bei emerged victorious and took control of Hanzhong in 219, subsequently declaring himself "King of Hanzhong" in autumn that year.

Background
In 215, Cao Cao attacked the warlord Zhang Lu in Hanzhong commandery, defeating the latter at the Battle of Yangping. Zhang Lu surrendered and Hanzhong came under Cao Cao's control.

On Liu Bei's side, he had also recently seized control of Yi Province (covering present-day Sichuan and Chongqing) from Liu Zhang, and was in the midst of a dispute with his ally Sun Quan over Jing Province (covering present-day Hubei and Hunan). Liu Bei felt threatened when he received news that Hanzhong had fallen to Cao Cao, because Hanzhong was the northern "gateway" into Yi Province, and he was now in danger of losing his home base to Cao Cao. Hence, Liu Bei came to a border treaty with Sun Quan, who had seized Changsha (長沙), Guiyang (桂陽), and Lingling (零陵) from him. Liu Bei asked Sun Quan to divert Cao Cao's attention by attacking Hefei and demanded Lingling back. In return, he recognised Sun Quan's control over Jing Province's commanderies of Changsha, Jiangxia (江夏) and Guiyang.

Strategic difference
In Hanzhong, Sima Yi and Liu Ye urged Cao Cao to use the opportunity to attack Yi Province, but Cao rejected the idea, saying, "We should not be discontent. Now that we've already conquered Longyou (referring to present-day eastern Gansu), you're still longing about merging Shu (referring to Yi Province)!" Cao Cao then left his generals Xiahou Yuan, Zhang He and Xu Huang behind to defend Hanzhong, and his Chief Clerk (長史) Du Xi to oversee affairs in Hanzhong.

In 217, Liu Bei's advisor Fa Zheng analysed the reason Cao Cao left Xiahou Yuan to guard Hanzhong-- the newly conquered Hanzhong was still unstable (partly due to the massive relocation enforced by Cao Cao). Fa Zheng also believed Xiahou Yuan and Zhang He were not good commanders, so the pair could not defend the commandery. Hence, Fa Zheng urged Liu Bei to attack Hanzhong, stating three advantages if the commandery was in Liu's control: the ideal usage of Hanzhong was that it served as a base of operations to attack Cao Cao and revive the Han Dynasty; a decent usage of Hanzhong was that Liu Bei could attack Yong and Liang provinces from it (Hanzhong granted access to the two provinces) and expand his territory; a more conservative mean was that defense of Hanzhong could be a long-lasting strategy for the survival of the Shu regime. Liu Bei agreed to Fa Zheng's insight and ordered him to plan for the upcoming campaign.

Initial clashes
In 217, Liu Bei followed Huang Quan's strategy and defeated the enemy generals Pu Hu (朴胡) and Du Huo (杜濩), taking control of Badong (巴東) and Baxi (巴西) commanderies, which were respectively guarded by them previously. Liu Bei's army then advanced towards Yangping Pass (陽平關) near Hanzhong. At the same time, Liu Bei also sent Zhang Fei, Ma Chao, Wu Lan (吳蘭), Lei Tong and Ren Kui (任夔) to attack Wudu (武都) commandery, and they garrisoned at Xiabian (下辨). During this time, Lei Ding (雷定) of the Di ethnic group led seven tribes to join Liu Bei. As for Cao Cao's side, Xiahou Yuan defended Yangping Pass, Zhang He and Xu Huang respectively guarded Guangshi (廣石) and Mamingge (馬鳴閣), while Cao Hong and Cao Xiu led a separate force to resist Zhang Fei.

In 218, Zhang Fei and Ma Chao's army garrisoned at Mount Gu (固山), where they spread news that they were going to blockade the enemy's retreat route. Cao Hong wanted to attack Wu Lan at Xiabian, but the other generals were suspicious of Zhang Fei's movements. Cao Xiu thought that if Zhang Fei was really planning to seal their retreat route, he should keep his plan covert; now that Zhang Fei had overtly revealed his intention, they should make use of the opportunity to feign retreat and perform a frontal assault. Cao Hong consented to Cao Xiu's tactic and attacked. Lei Tong and Ren Kui were killed in battle, while Wu Lan fled to join the Di tribes, where he was subsequently killed by a Di leader, Qiang Duan. After such a defeat, Zhang Fei and Ma Chao withdrew their army by the third lunar month.

On another front, Liu Bei was facing Xiahou Yuan at Yangping Pass. In the seventh lunar month, Liu Bei sent Chen Shi to attack Mamingge, but the latter was defeated by Xu Huang, and some of the fleeing soldiers fell into the deep valleys during their escape. Liu Bei personally led an assault on Zhang He at Guangshi but was unable to overcome his enemy. He then sent an urgent letter to Zhuge Liang in his capital, Chengdu, requesting for reinforcements. Zhuge Liang vacillated and consulted Yang Hong (楊洪), who said, "Hanzhong is the throat of Yi Province. This is a critical point of survival and destruction. Without Hanzhong there will be no Shu (Yi Province). A disaster has befallen on the gates of our home. At this moment, the men should go to war, the women should help in transporting supplies, what's there to hesitate about sending reinforcements?" Zhuge Liang accepted Yang Hong's advice and sent a relief force to Liu Bei, as Liu Bei continued his standoff against Cao Cao's forces.

Turn of the tide
In the ninth lunar month of 218, Cao Cao moved from Ye City to Chang'an near Hanzhong to direct the defence against Liu Bei, but had been held up by internal problems including a major coup d'état and some local uprisings. In the meantime, Liu Bei and Xiahou Yuan had been locked in a stalemate for a year. In the first lunar month of 219, to break the deadlock, Liu Bei crossed the Mian River (沔水) south of Yangping Pass and advanced towards Hanzhong through the mountains. Liu Bei's army set up camp at Mount Dingjun. In response, Xiahou Yuan and Zhang He led their forces out in an attempt to take control of higher ground, and they made camp at Zouma Valley (走馬谷). During the night, Liu Bei followed Huang Quan's plan and set fire to the enemy camp fences. Xiahou Yuan led a force to defend the southern flank while sending Zhang He to guard the eastern side. Liu Bei launched a direct assault on Zhang He and Zhang started to falter, so Xiahou Yuan despatched half of his forces to support Zhang. At this point, Fa Zheng told Liu Bei that it was an opportune time to attack. Liu Bei ordered his men to shout loudly and beat the drums, and sent Huang Zhong to charge at the enemy. The mettlesome soldiers of Huang Zhong broke through the enemy lines and slew Xiahou Yuan and Zhao Yong (趙顒), while Zhang He fled with his surviving troops to north of the Han River, where they set up camp.

As Cao Cao's forces had just lost their commander, Xiahou Yuan, a tempest ensued. Du Xi and Guo Huai regrouped their scattered troops and (unofficially) nominated Zhang He to replace Xiahou Yuan. Zhang He accepted and gave orders to his troops, restoring peace and order in his army. The following day, Liu Bei planned to cross the Han River and attack Zhang He, whose officers pointed out they were outnumbered, and suggested to Zhang to set up camps along the Han riverbank. Guo Huai felt that their forces were displaying weakness to the enemy by doing so, he proposed setting up camp far away from the river to lure the enemy to cross the shallow, during which they counterattack the enemy. Zhang He agreed with Guo Huai's idea and moved his camp further away from the river. Liu Bei became suspicious and did not dare to cross the river. In Chang'an, when Cao Cao heard that Xiahou Yuan had been killed in action, he despatched Cao Zhen with an army to reinforce their forces at Yangping Pass. When Cao Zhen arrived, he directed Xu Huang to attack Liu Bei's general Gao Xiang. Xu Huang scored a victory and temporarily restored some morale for Cao Cao's side.

Battle of Han River
In the third lunar month of 219, Cao Cao personally led an army from Chang'an to Hanzhong via Xia Valley (斜谷). Liu Bei was not worried, as he thought, "Even if Cao Cao came, he cannot do anything. I'll definitely take control of the Han River." Hence, Liu Bei gathered his forces and put up a firm defence, refusing to engage Cao Cao's army.

Later, when Cao Cao's forces were transporting supplies via Beishan (北山), Huang Zhong led a force to rob the enemy's supplies, but had yet to return on time. Zhao Yun led ten horsemen out of camp in search of Huang Zhong and encountered Cao Cao's army. They were surrounded but Zhao Yun fought his way out and retreated back to camp with the enemy in pursuit. Upon reaching camp, Zhao Yun ordered the gates to be opened, flags and banners to be lowered, and the beating of war drums to be stopped. Cao Cao's men feared an ambush in the camp and turned back. Just then, Zhao Yun ordered his troops to beat the drums loudly and his archers to rain arrows on the enemy. Cao Cao's soldiers were thrown into confusion and trampled on each other as they attempted to flee, while many drowned as they tried to escape across the Han River.

As Cao Cao had been in a standoff against Liu Bei for several months and had been facing serious logistics problem, he eventually gave an order, "chicken rib" (雞肋). Cao Cao's men were puzzled as they did not understand what "chicken rib" meant, except for Cao Cao's registrar Yang Xiu. Yang Xiu explained that it was a pity to discard chicken's rib, even though it did not have much meat to be eaten. This was an analogy to the situation Cao Cao was facing: Cao knew that he had little chance of defeating Liu Bei, but felt that it was a pity to just relinquish Hanzhong and withdraw. By the fifth lunar month, Cao Cao retreated back to Chang'an and gave up Hanzhong to Liu Bei.

Aftermath
A month after successfully conquering Hanzhong, Liu Bei sent Meng Da to attack Fangling (房陵) via Zigui (秭歸). Meng Da defeated and killed Fangling's Administrator, Kuai Qi (蒯祺), and took control of the area. Liu Bei later sent his adopted son, Liu Feng, to attack Shangyong (上庸) via sailing down the Mian River (沔水) from Hanzhong. Shangyong's Administrator Shen Dan (申耽) surrendered to Liu Feng. In the seventh lunar month of 219, Liu Bei declared himself "King of Hanzhong".

On the other hand, after withdrawing, Cao Cao was worried that Liu Bei might attack Wudu (武都) commandery, so he ordered the Inspector (刺史) of Yong Province, Zhang Ji, to relocate 50,000 Di people from Wudu to Fufeng (扶風) and Tianshui (天水) commanderies.

Liu Bei forces

 * Director of Retainers (司隸校尉) Liu Bei
 * General Who Spreads Martial Might (揚武將軍) Fa Zheng
 * Protector of the Army (護軍) Huang Quan
 * General Who Attacks Barbarians (討虜將軍) Huang Zhong
 * General of the Standard (牙門將軍) Wei Yan
 * Vice General of the Household in the Army (副軍中郎將) Liu Feng
 * Chen Shi
 * Gao Xiang


 * Assisting General of the Army (翊軍將軍) Zhao Yun
 * Zhang Zhu (張著)


 * General Who Attacks Barbarians (征虜將軍) Zhang Fei
 * General Who Pacifies the West (平西將軍) Ma Chao
 * Wu Lan (吳蘭)
 * Lei Tong
 * Ren Kui (任夔)

Cao Cao forces

 * King of Wei (魏王) Cao Cao
 * Protector of the Army Who Attacks Shu (征蜀護軍) Cao Zhen
 * Registrar (主簿) Yang Xiu
 * North General of the Household (北中郎將) Cao Zhang


 * General Who Attacks the West (征西將軍) Xiahou Yuan
 * Inspector of Yi Province (益州刺史) Zhao Yong (趙顒)
 * General Who Rocks Bandits (盪寇將軍) Zhang He
 * Imperial Son-in-Law and Commandant (駙馬都尉) Du Xi
 * Major (司馬) Guo Huai
 * Xiahou Rong (夏侯榮)


 * Protector-General (都護將軍) Cao Hong
 * Cavalry Commandant (騎都尉) Cao Xiu
 * Administrator of Wudu (武都太守) Yang Fu


 * General Who Pacifies Bandits (平寇將軍) Xu Huang


 * Pu Hu (朴胡)
 * Du Huo (杜濩)