Zhuge Liang's Northern Expeditions were a series of five military campaigns launched by the state of Shu Han against the rival state of Cao Wei from 228 to 234 during the Three Kingdoms period in China. All five expeditions were led by Zhuge Liang, the Imperial Chancellor and regent of Shu after the Kingdoms of Wei and Shu were established. Although they proved unsuccessful and ended up as a stalemate, the expeditions have become some of the best-known conflicts of the Three Kingdoms period and one of its few battles during which each side (Shu and Wei) fought with hundreds of thousands of troops, as opposed to other battles in which one side had a huge numerical advantage.
The expeditions are dramatised and romanticised in the 14th-century historical novel Romance of the Three Kingdoms, which includes the famous scene of the Empty Fort Strategy.
Background
In 220, following the end of the Han dynasty, China was divided into three competing regimes: Cao Wei (or Wei), Shu Han (or Shu) and Eastern Wu (or Wu). Each of them was trying to unify the country under its rule.
In Shu, the strategic thinking behind the Northern Expeditions came from Zhuge Liang's Longzhong Plan, which he presented to the warlord Liu Bei in 207. In essence, the plan envisaged a tripartite division of China between the domains of the warlords Liu Bei, Cao Cao and Sun Quan. According to the plan, Liu Bei would seize control of Jing Province and Yi Province from their respective governors, Liu Biao and Liu Zhang, and establish a solid foothold in southern and western China. Liu Bei would then form an alliance with Sun Quan, who ruled eastern China, and wage war against Cao Cao, who controlled northern China and the political centre of the Han dynasty in central China. Liu Bei would then lead one army from Yi Province to attack Chang'an via the Qin Mountains and Wei River valley; one of Liu Bei's top generals would lead another army from Jing Province to attack Luoyang.(亮荅曰：「自董卓已來，豪傑並起，跨州連郡者不可勝數。 ... 誠如是，則霸業可成，漢室可興矣。」) Sanguozhi vol. 35.
The first phase of the plan was completed in 214 when Liu Bei gained control of southern Jing Province and Yi Province. Between 217 and 219, Liu Bei launched a campaign to seize control of Hanzhong Commandery, the "northern gateway" into Yi Province, and succeeded in capturing it from Cao Cao's forces. In 219, Liu Bei's general Guan Yu, whom Liu Bei had left in charge of Jing Province, started the Battle of Fancheng against Cao Cao's forces. However, the Sun Quan–Liu Bei alliance ("Sun–Liu alliance"), which Zhuge Liang played an instrumental role in creating, broke down when Sun Quan sent his forces to attack and seize Liu Bei's territories in Jing Province while Guan Yu was away at the Battle of Fancheng. Guan Yu was captured and executed by Sun Quan's forces. Between 221 and 222, Liu Bei started the Battle of Xiaoting/Yiling against Sun Quan in an attempt to retake Jing Province, but failed and suffered a disastrous defeat. After Liu Bei died in 223, his son Liu Shan succeeded him as emperor of Shu, with Zhuge Liang serving as regent. The same year, Zhuge Liang made peace with Sun Quan's Eastern Wu regime and reestablished the Sun–Liu alliance (now the Wu–Shu alliance) against Wei, the regime established by Cao Cao's son and successor, Cao Pi.
In 227, Zhuge Liang ordered troops from throughout Shu to mobilise and assemble in Hanzhong Commandery in preparation for a large-scale military campaign against Wei. Before leaving, he wrote a memorial, called Chu Shi Biao (literally "memorial on the case to go to war"), and submitted it to Liu Shan. Among other things, the memorial contained Zhuge Liang's reasons for the campaign against Wei and his personal advice to Liu Shan on governance issues.[建興]五年，率諸軍北駐漢中，臨發，上疏曰：先帝創業未半， ... 不知所言。) Sanguozhi vol. 35. After Liu Shan approved, Zhuge Liang ordered the Shu forces to garrison at Mianyang (沔陽; present-day Mian County, Shaanxi).(遂行，屯于沔陽。) Sanguozhi vol. 35.
Geography
Zhuge Liang's plan called for a march north from Hanzhong Commandery (what is now southern Shaanxi Province), the main population centre in northern Yi Province. In the 3rd century, Hanzhong Commandery was a sparsely-populated area surrounded by wild virgin forest. Its importance lay in its strategic placement in a long and fertile plain along the Han River, between two massive mountain ranges, the Qin Mountains in the north and the Micang Mountains in the south. It was the major administrative centre of the mountainous frontier district between the rich Sichuan Basin in the south and the Wei River valley in the north. The area also afforded access to the dry northwest and the Gansu panhandle.
Geographically, the rugged barrier of the Qin Mountains provided the greatest obstacle to Chang'an. The mountain range consists of a series of parallel ridges, all running slightly south of east, separated by a maze of ramifying valleys whose canyon walls often rise sheer above the valley streams. As a result of local dislocations from earthquakes, the topographical features are extremely complicated.
Access from the south was limited to a few mountain routes called "gallery roads," which crossed major passes and were remarkable for their engineering skill and ingenuity. The oldest of them was northwest of Hanzhong Commandery and crossed the San Pass. The Lianyun "Linked Cloud" Road was constructed there to take carriage traffic during the Qin dynasty, in the 3rd century BCE. Following the Jialing Valley, the route emerges in the north where the Wei River widens considerably near Chencang (in present-day Baoji, Shaanxi). Another important route was the Baoye route, which transverses the Yegu Pass and ends south of Mei County. A few more minor and difficult routes lay to the east, notably the Ziwu Valley, which leads directly to the south of Chang'an.
Xincheng Rebellion
Meng Da, a former Shu general who defected to Wei in 220, served as the Administrator of Xincheng Commandery (新城郡; in present-day northwestern Hubei) near Shu's northeastern border. Zhuge Liang hated Meng Da for his capricious behaviour and worried that he would become a threat to Shu.(蜀相諸葛亮惡其反覆，又慮其為患。) Jin Shu vol. 1. Around 227, when he heard that Meng Da had a quarrel with his colleague Shen Yi (申儀), he sent spies to stir up greater suspicions between them and spread news that Meng Da was plotting a rebellion against Wei. Meng Da became fearful and decided to rebel.(諸葛亮聞之，陰欲誘達，數書招之，達與相報答。魏興太守申儀與達有隙，密表達與蜀潛通，帝未之信也。司馬宣王遣參軍梁幾察之，又勸其入朝。達驚懼，遂反。) Weilüe annotation in Sanguozhi vol. 3. However, he was stuck in a dilemma after receiving a letter from the Wei general Sima Yi, who was stationed at Wancheng. In the meantime, Sima Yi quickly assembled an army, headed towards Xincheng, and reached there within eight days.(帝恐達速發， ... 達得書大喜，猶與不決。帝乃潛軍進討。諸將言達與二賊交構，宜觀望而後動。帝曰：「達無信義，此其相疑之時也，當及其未定促決之。」乃倍道兼行，八日到其城下。) Jin Shu vol. 1.
Wei's rival states, Shu and Wu, sent forces to support Meng Da but were defeated and driven back by Wei forces led by Sima Yi's subordinates.(吳蜀各遣其將向西城安橋、木闌塞以救達，帝分諸將以距之。) Jin Shu vol. 1. Sima Yi ordered his troops to surround Shangyong (上庸), Meng Da's base, and attack from eight directions. At the same time, he also successfully induced Meng Da's nephew Deng Xian (鄧賢) and subordinate Li Fu (李輔) to betray Meng Da. After 16 days of siege, Deng Xian and Li Fu opened Shangyong's gates and surrendered to Sima Yi. Meng Da was captured and executed.(上庸城三面阻水，達於城外為木柵以自固。帝渡水，破其柵，直造城下。八道攻之，旬有六日，達甥鄧賢、將李輔等開門出降。斬達，傳首京師。) Jin Shu vol. 1.(二年春正月，宣王攻破新城，斬達，傳其首。) Sanguozhi vol. 3.(魏略曰：宣王誘達將李輔及達甥鄧賢，賢等開門納軍。達被圍旬有六日而敗，焚其首於洛陽四達之衢。) Weilüe annotation in Sanguozhi vol. 3. Sima Yi and his troops headed back to Wancheng after suppressing the rebellion.(俘獲萬餘人，振旅還于宛。) Jin Shu vol. 1. He then went to the Wei capital, Luoyang, to report to Wei emperor Cao Rui and then returned to Wancheng.(... 歸于京師。 ... 屬帝朝于京師，天子訪之於帝。 ... 天子並然之，復命帝屯于宛。) Jin Shu vol. 1.
First expedition
In the spring of 228, Zhuge Liang launched the first Northern Expedition and led the Shu forces to Mount Qi (祁山; the mountainous regions around present-day Li County, Gansu). At the same time, he ordered Zhao Yun and Deng Zhi to lead a decoy force to Ji Valley (箕谷) and pretend to be ready to attack Mei County, so as to divert the Wei forces' attention away from Mount Qi. News of the Shu invasion sent shockwaves throughout the Guanzhong region. Three Wei-controlled commanderies – Nan'an (南安), Tianshui and Anding (安定) – defected to the Shu side.([建興]六年春，揚聲由斜谷道取郿，使趙雲、鄧芝為疑軍，據箕谷，魏大將軍曹真舉衆拒之。亮身率諸軍攻祁山，戎陣整齊，賞罰肅而號令明，南安、天水、安定三郡叛魏應亮，關中響震。) Sanguozhi vol. 35.
In response to the Shu invasion, Cao Rui moved from Luoyang to Chang'an to oversee the defence and to provide backup. He ordered Zhang He to attack Zhuge Liang at Mount Qi, and Cao Zhen to attack Zhao Yun and Deng Zhi at Ji Valley.([建興]五年，隨諸葛亮駐漢中。明年，亮出軍，揚聲由斜谷道，曹真遣大衆當之。亮令雲與鄧芝往拒，而身攻祁山。雲、芝兵弱敵彊，失利於箕谷，然歛衆固守，不至大敗。) Sanguozhi vol. 36. Zhao Yun and Deng Zhi lost the Battle of Ji Valley because their decoy force, composed of the weaker soldiers in the Shu army, were no match for Cao Zhen and his well-trained troops. (Zhuge Liang had reserved the better troops for the attack on Mount Qi.) In the meantime, Zhuge Liang sent Ma Su to lead the vanguard force to engage Zhang He at Jieting (街亭; located east of present-day Qin'an County, Gansu). Ma Su not only disobeyed Zhuge Liang's orders but also made the wrong moves, which resulted in the Shu vanguard suffering a disastrous defeat. After his victory at the Battle of Jieting, Zhang He seized the opportunity to attack and to recapture the three commanderies.(諸葛亮出祁山。加郃位特進，遣督諸軍，拒亮將馬謖於街亭。謖依阻南山，不下據城。郃絕其汲道，擊，大破之。南安、天水、安定郡反應亮，郃皆破平之。) Sanguozhi vol. 17.(亮使馬謖督諸軍在前，與郃戰于街亭。謖違亮節度，舉動失宜，大為郃所破。) Sanguozhi vol. 35.
Upon learning of the Shu defeats at Ji Valley and Jieting, Zhuge Liang pulled back all his forces and retreated to Hanzhong. Although the first Northern Expedition was an overall failure, Zhuge Liang still made some small gains for Shu. The first gain was the capture of some Wei civilian families, which were then registered as Shu citizens and resettled in Hanzhong.
The second gain was the defection of Jiang Wei, a low-ranking Wei officer who later became a prominent Shu general. After returning to Hanzhong, Zhuge Liang executed Ma Su to appease public anger(亮拔西縣千餘家，還于漢中，戮謖以謝衆。) Sanguozhi vol. 35. and then wrote a memorial to Liu Shan, taking full responsibility for the failure of the first Northern Expedition and requesting to be punished by demotion.(上疏曰：「臣以弱才，叨竊非據，親秉旄鉞以厲三軍，不能訓章明法，臨事而懼，至有街亭違命之闕，箕谷不戒之失，咎皆在臣授任無方。臣明不知人，恤事多闇，春秋責帥，臣職是當。請自貶三等，以督厥咎。」) Sanguozhi vol. 35. Liu Shan approved and symbolically demoted Zhuge Liang from Imperial Chancellor (丞相) to General of the Right (右將軍) but allowed him to remain as acting Imperial Chancellor.(於是以亮為右將軍，行丞相事，所總統如前。) Sanguozhi vol. 35.
Second expedition
In the winter of 228–229, Zhuge Liang launched the second Northern Expedition and led Shu forces to attack the Wei fortress at Chencang via San Pass. When he showed up at Chencang, he was surprised to see that it was much more heavily fortified and well defended than he had expected. That was because after the first Northern Expedition, the Wei general Cao Zhen had predicted that Shu forces would attack Chencang the next time and so he put Hao Zhao in charge of defending Chencang and strengthening its defenses.(真以亮懲於祁山，後出必從陳倉，乃使將軍郝昭、王生守陳倉，治其城。明年春，亮果圍陳倉，已有備而不能克。) Sanguozhi vol. 9.(大和中，魏遣將軍郝昭築城陳倉城。適訖，㑹諸葛亮來攻。亮本聞陳倉城惡，及至，怪其整頓，聞知昭在其中，大驚愕。) Taiping Huanyu Ji vol. 30.