Deng Ai (197 – late March 264Vol.04 of Sanguozhi and vol.02 of Jin Shu both indicated that Deng Ai was arrested in the 1st month of the 1st year of the Xianxi era. The month corresponds to 15 Feb to 14 Mar 264 in the Julian calendar. Volume 78 of Zizhi Tongjian dated Deng Ai's arrest to the renchen day of that month, but there is no renchen day in that month. The next renchen day is in the 2nd month, and corresponds to 16 Mar 264 in the Julian calendar. All sources agree that Deng Ai died after Zhong Hui, who died on 3 Mar 264.), courtesy name Shizai, was a Chinese military general and politician of the state of Wei during the Three Kingdoms period of China. He is best known for his pivotal role in the Wei conquest of its rival state, Shu, in late 263. He was described as a very loyal subject who made great contributions to Wei, but was also noted for his arrogance and audacity, which led to his downfall and death.
Born in a peasant family, Deng Ai started his career as a minor agricultural officer. Sometime between 235 and 239, he met Sima Yi, who recognised his talent and gave him a higher position in the civil service. Around this time, he also wrote a proposal on starting agricultural works in the Huai River region, and received credit for his ideas. Deng Ai gained greater prominence in Wei from 249 onwards after he joined the Wei general Guo Huai in stopping a Shu invasion. He also advised the regent Sima Shi on some issues. In 255, he participated in the suppression of a rebellion started by the generals Guanqiu Jian and Wen Qin, and was promoted to the status of a top general. From 255 to 262, he defended Wei's western borders in present-day Gansu from multiple incursions by the Shu forces led by the general Jiang Wei.
Deng Ai reached the pinnacle of his career in 263, when he led Wei forces to conquer Shu. By leading a strike force through a shortcut across dangerous mountainous terrain, Deng Ai showed up in the vicinity of the Shu capital, Chengdu, and took the enemy by surprise. After a failed attempt by the Shu general Zhuge Zhan to stop Deng Ai at Mianzhu, the Shu emperor Liu Shan voluntarily surrendered to Deng Ai and brought an end to the Shu state. Following his success in the Shu campaign, Deng Ai became arrogant about his achievements and showed disregard for the Wei government's authority. The Wei general Zhong Hui exploited and manipulated Deng Ai's arrogance to great effect. In 264, Deng Ai was arrested by Wei Guan and Zhong Hui, who were acting under order by the Wei regent Sima Zhao. He was placed in a prison cart and escorted to the capital Luoyang, but was killed en route by soldiers sent by Wei Guan. His sons were executed as well. His surviving family members were exiled but allowed to return in 266 after the Jin dynasty was established.
Early life and career Deng Ai was from Jiyang County (棘陽縣), Yiyang Commandery (義陽郡), which is around present-day Xinye County, Henan. He was born towards the end of the Eastern Han dynasty and lost his father at a young age. When the warlord Cao Cao conquered northern Jing Province in 208, Deng Ai moved to Runan Commandery (汝南郡; in present-day southern Henan), where he lived as a farmer and raised cattle. When he was 11 years old, he and his mother passed by Chen Shi's tomb in Yingchuan Commandery (潁川郡; around present-day Xuchang, Henan). He read two lines engraved on Chen Shi's tombstone: "his writings became examples of excellent prose; his conduct served as a role model for scholar-officials" (文為世範，行為士則). He was so inspired that he wanted to change his given name to Fan (literally "(role) model") and his courtesy name to Shize (literally "for scholar-officials to emulate"). However, since the names Fan and Shize were already used by members of his extended family, he could not change his names as such because it would violate the naming taboo.(鄧艾字士載，義陽棘陽人也。少孤，太祖破荊州，徙汝南，為農民養犢。年十二，隨母至潁川，讀故太丘長陳寔碑文，言「文為世範，行為士則」，艾遂自名範，字士則。後宗族有與同者，故改焉。) Sanguozhi vol. 28.
Deng Ai later became an academician () under the Commandant of Xiangcheng (襄城; present-day Xiangcheng County, Henan). However, he was not too successful in his career because he stuttered in his speech. He then switched his job to an agricultural officer in charge of grain and fodder. The locals pitied him for his poor family background and often provided him with financial aid. Deng Ai initially did not show any form of gratitude towards them. Whenever he saw mountains and lakes, he started gesturing and pointing out how and where he believed army camps should be laid out, but was scorned by others. Later on, he was promoted to a clerical position which put him in charge of maintaining records of agricultural output.(為都尉學士，以口吃，不得作幹佐。為稻田守叢草吏。同郡吏父怜其家貧，資給甚厚，艾初不稱謝。每見高山大澤，輙規度指畫軍營處所，時人多笑焉。後將典農綱紀，上計吏， ...) Sanguozhi vol. 28.
Deng Ai had an acquaintance, Shi Bao (; father of Shi Chong), who was about the same age as him. They were quite close to Guo Xuanxin (), who served as an Internuncio (). When Ji Ben, an imperial physician, started a rebellion in Xu (許; present-day Xuchang, Henan) in 218, Guo Xuanxin was implicated and initially placed under house arrest until an officer came to escort him to the imperial capital for trial. Deng Ai and Shi Bao were among the escorts. While travelling for about ten li, Guo Xuanxin chatted with them along the way and remarked that the two of them would become very capable officials in the future. Deng Ai was later promoted to the rank of an Agricultural Officer of Merit ().(世語曰：鄧艾少為襄城典農部民，與石苞皆年十二三。謁者陽翟郭玄信，武帝監軍郭誕元弈之子。建安中，少府吉本起兵許都，玄信坐被刑在家，從典農司馬求入御，以艾、苞與御，行十餘里，與語，恱之，謂二人皆當遠至為佐相。艾後為典農功曹，奉使詣宣王，由此見知，遂被拔擢。) Shiyu annotation in Sanguozhi vol. 28. This anecdote was also recorded in Shi Bao's biography in Book of Jin, albeit in lesser detail. (县召为吏，给农司马。会谒者阳翟郭玄信奉使，求人为御，司马以苞及邓艾给之。行十馀里，玄信谓二人曰：“子後并当至卿相。”苞曰：“御隶也，何卿相乎？”) Jin Shu, vol.33
Sometime between 235 and 239, he was sent as a messenger to the capital, Luoyang, where, by chance, he met Sima Yi, who was then serving as the Grand Commandant () under the Wei government. Sima Yi felt that Deng Ai was an extraordinary person so he recruited him and promoted him to the position of a Gentleman of Writing ().(... 因使見太尉司馬宣王。宣王奇之，辟之為掾，遷尚書郎。) Sanguozhi vol. 28.
Agricultural and irrigation projects Around the time, the Wei state was planning to promote agriculture and stockpile food resources in preparation for military campaigns against its rival states, Shu and Wu. Deng Ai was sent to survey the lands from the east of Chen () and Xiang () commanderies (around present-day Zhoukou, Henan) to Shouchun (壽春; around present-day Shou County, Anhui), and assess their suitability for agriculture. He saw that the lands were fertile but lacked moisture, so they were not fully utilised. He suggested digging irrigation channels to irrigate the land, and open up new canals for transporting goods by water.(時欲廣田畜糓，為滅賊資，使艾行陳、項已東至壽春。艾以為「田良水少，不足以盡地利，宜開河渠，可以引水澆溉，大積軍糧，又通運漕之道。」) Sanguozhi vol. 28.
Deng Ai wrote a proposal, the Ji He Lun (濟河論; Discussion on the River), to explain his ideas:(乃著濟河論以喻其指。) Sanguozhi vol. 28. Sima Yi agreed with Deng Ai's proposal and implemented his ideas.(宣王善之，事皆施行。) Sanguozhi vol. 28.
In 241, the agricultural projects were complete. Whenever there were battles in the southeast between Wei and Wu, the Wei forces could sail down the river towards the Huai River region to counter the enemy. This was because they had plenty of food supplies stockpiled upstream and had the water pathways to their advantage. Deng Ai received credit for his proposal.(正始二年，乃開廣漕渠，每東南有事，大軍興衆，汎舟而下，達于江、淮，資食有儲而無水害，艾所建也。) Sanguozhi vol. 28.
Battle of Tao River
Deng Ai later became a military adviser to the Wei general Xiahou Xuan and served as the Administrator of Nan'an Commandery (南安郡; around present-day Longxi and Wushan counties, Gansu). In 249, he followed Xiahou Xuan's successor Guo Huai to resist an invasion led by the Shu general Jiang Wei. After the Shu forces were repelled, Guo Huai advanced west to attack the Qiang tribes. Deng Ai cautioned him: "The enemy did not retreat far. They might turn back to attack us again, so we should split up our forces in case they attack us again."(出參征西軍事，遷南安太守。嘉平元年，與征西將軍郭淮拒蜀偏將軍姜維。維退，淮因西擊羌。艾曰：「賊去未遠，或能復還，宜分諸軍以備不虞。」) Sanguozhi vol. 28.
Guo Huai then ordered Chen Tai, Xu Zhi and Deng Ai to lead Wei forces to attack the fortresses at Qushan and cut off their food and water supplies. Ju An and Li Xin led their men to taunt Deng Ai to attack them, but Deng Ai ignored them. As time passed, the two fortresses gradually ran out of supplies. Jiang Wei led his troops from Mount Niutou (牛頭山; west of present-day Zhaohua District, Guangyuan, Sichuan) to reinforce the fortresses. They encountered Chen Tai and his troops along the way. Chen Tai said: "The Art of War says that the best way to win a battle is to win without fighting. If we manage to occupy Mount Niutou, Jiang Wei's return route will be sealed off and he can be easily captured by us." He then ordered his troops to build forts to resist Jiang Wei's forces but refrain from engaging the enemy. At the same time, he also wrote to Guo Huai and requested his help in attacking Mount Niutou. Guo Huai did so and led his troops across the Tao River in preparation for attacking Mount Niutou.(淮從泰計，使泰率討蜀護軍徐質、南安太守鄧艾等進兵圍之，斷其運道及城外流水。安等挑戰，不許，將士困窘，分糧聚雪以稽日月。維果來救，出自牛頭山，與泰相對。泰曰：「兵法貴在不戰而屈人。今絕牛頭，維無反道，則我之禽也。」勑諸軍各堅壘勿與戰，遣使白淮，欲自南渡白水，循水而東，使淮趣牛頭，截其還路，可并取維，不惟安等而已。淮善其策，進率諸軍軍洮水。維懼，遁走，安等孤縣，遂皆降。) Sanguozhi vol. 22.(淮乃使泰率討蜀護軍徐質、南安太守鄧艾進兵圍麴城，斷其運道及城外流水。安等挑戰，不許，將士困窘，分糧聚雪以引日月。維引兵救之，出自牛頭山，與泰相對。泰曰：「兵法貴在不戰而屈人。今絕牛頭，維無反道，則我之禽也。」敕諸軍各堅壘勿與戰，遣使白淮，使淮趣牛頭截其還路。淮從之，進軍洮水。) Zizhi Tongjian vol. 75.
Deng Ai remained behind and garrisoned at the north of Baishui County. Three days later, Jiang Wei sent Liao Hua to lead a force to approach Deng Ai's camp from the south of Baishui. Deng Ai told his officers: "Jiang Wei has turned back to attack us. We have few troops. Ideally, we should cross the river and not build a bridge. I believe Jiang Wei must have sent Liao Hua to hinder us so that we are forced to remain here, while he would attack Taocheng (洮城) from the east." Taocheng was located north of the river and was about 60 li away from Deng Ai's position. Deng Ai immediately dispatched troops to travel overnight to Taocheng to defend the fortress. As he expected, Jiang Wei crossed the river to attack Taocheng, but failed to capture the fortress because Deng Ai had already strengthened its defences. For his achievements, Deng Ai was enfeoffed as a Secondary Marquis (), awarded the rank of General Who Attacks Rebels (), and subsequently appointed as the Administrator of Chengyang Commandery (城陽郡; around present-day Zhucheng, Shandong).(於是留艾屯白水北。三日，維遣廖化自白水南向艾結營。艾謂諸將曰：「維今卒還，吾軍人少，法當來渡而不作橋。此維使化持吾，令不得還。維必自東襲取洮城。」洮城在水北，去艾屯六十里。艾即夜潛軍徑到，維果來渡，而艾先至據城，得以不敗。賜爵關內侯，加討寇將軍，後遷城陽太守。) Sanguozhi vol. 28.
Military advisor service Around the time, the Xiongnu prince Liu Bao, who was nominally a vassal under the Wei government, unified the Five Divisions of Xiongnu in Bing province and was building up his military force. Deng Ai wrote a memorial to the Wei imperial court:(是時并州右賢王劉豹并為一部， ...) Sanguozhi vol. 28.