Fa Zheng (176–220), courtesy name Xiaozhi, was a key adviser to the warlord Liu Bei in the late Eastern Han dynasty. Born in a family of high social status and of noble descent, Fa Zheng travelled to Yi Province (covering present-day Sichuan and Chongqing) in the late 190s and became a subordinate of Liu Zhang, the provincial governor. However, his feelings of alienation and perception of Liu Zhang as an incompetent governor eventually led him to betray Liu Zhang and defect to Liu Bei in 211. Between 211 and 214, Fa Zheng assisted Liu Bei in overcoming Liu Zhang and seizing control of Yi Province, and became one of Liu Bei's most trusted advisers. In 217, he urged Liu Bei to launch the Hanzhong Campaign to capture the strategic Hanzhong Commandery from a rival warlord, Cao Cao, but died a year after Liu emerged victorious in the campaign.
Fa Zheng's keen foresight and brilliance in formulating strategies earned him praise from his contemporaries such as Zhuge Liang and Chen Shou. In less than a decade serving under Liu, Fa showed a near unmatched sense of timing where military geniuses like Cao Cao and his best advisers fell victim to his schemes. However, he was also notorious for his vindictive personality. When he held office, he abused his power by taking revenge against those who had offended him before, and by killing them without reason. Nevertheless, he was still highly regarded and trusted by Liu Bei – to the point where Zhuge Liang once said that Fa Zheng might have been the only person capable of preventing Liu Bei's defeat at the Battle of Xiaoting in 221 if he were still alive.
Family background Fa Zheng's ancestral home was in Mei County (), Youfufeng Commandery (), which is in present-day Mei County, Shaanxi. His ancestor was Tian Fazhang, who is historically known as King Xiang of the Qi state in the Warring States period. Tian Fazhang's descendants changed their family name from "Tian" to "Fa" after the fall of Qi in 221 BCE.(法雄字文彊，扶風郿人也，齊襄王法章之後。秦滅齊，子孫不敢稱田姓，故以法為氏。宣帝時，徙三輔，世為二千石。) Houhanshu vol. 38.
Fa Zheng's great-grandfather, Fa Xiong, served as the Administrator () of Nan Commandery (南郡; around present-day Jingzhou, Hubei) during the reign of Emperor An in the Eastern Han dynasty. Fa Zheng's grandfather, Fa Zhen, was a reclusive scholar known for his lofty character; despite being a learned scholar, he led a humble life and repeatedly rejected offers to serve in the government.(法正字孝直，右扶風郿人也。祖父真，有清節高名。) Sanguozhi vol. 37. Fa Zheng's father, Fa Yan (), whose courtesy name was Jimou (), also served as a government official and held the positions of an assistant to the Excellency over the Masses () and the Minister of Justice ().(三輔決錄注曰：真字高卿， ... 正父衍，字季謀，司徒掾、廷尉左監。) Sanfu Jue Lu Zhu annotation in Sanguozhi vol. 37.
Service under Liu Zhang In the early Jian'an era (196–220) of the reign of Emperor Xian, when famines broke out, Fa Zheng and his friend Meng Da (who was from the same commandery) travelled to Yi Province (covering present-day Sichuan and Chongqing) to join the provincial governor, Liu Zhang. Fa Zheng served as the Prefect () of Xindu County () and later as a Colonel Who Advises the Army () under Liu Zhang. Since he didn't have any connections with local clans and was defamed by other refugees from Youfufeng, who had also moved to Yi Province, he couldn't realize his ambitions. He maintained a close friendship with his colleague Zhang Song, who shared the same views as him about Liu Zhang being an incompetent and incapable governor.(建安初，天下饑荒，正與同郡孟達俱入蜀依劉璋，乆之為新都令，後召署軍議校尉。旣不任用，又為其州邑俱僑客者所謗無行，志意不得。益州別駕張松與正相善，忖璋不足與有為，常竊歎息。) Sanguozhi vol. 37.
In 208,Zizhi Tongjian vol. 65. Zhang Song travelled to Jing Province (covering present-day Hubei and Hunan) to meet the warlord Cao Cao, who controlled the Han central government and the figurehead Emperor Xian. After returning to Yi Province, Zhang Song advised Liu Zhang to break ties with Cao Cao and build friendly relations with another warlord, Liu Bei. When Zhang Song recommended Fa Zheng to be Liu Zhang's representative to meet Liu Bei, Fa initially refused to accept the task but eventually relented. When Fa Zheng returned from his mission, he told Zhang Song that Liu Bei had grand ambitions and persuaded Zhang to follow him to serve Liu Bei. They wanted to help him secure Yi province but did not have the occasion to do so.(松於荊州見曹公還，勸璋絕曹公而自結先主。璋曰：「誰可使者？」松乃舉正，正辭讓，不得已而往。正旣還，為松稱說先主有雄略，密謀協規，願共戴奉，而未有緣。) Sanguozhi vol. 37.
Their opportunity came in 211,Zizhi Tongjian vol. 66. when Liu Zhang became fearful upon receiving news that Cao Cao was planning to attack the warlord Zhang Lu in Hanzhong Commandery. As Hanzhong Commandery was located strategically at the northern route leading into Yi Province, Liu Zhang would be in great peril if Hanzhong fell into Cao Cao's hands. Zhang Song proposed to Liu Zhang to invite Liu Bei to Yi Province to assist them in countering the threat posed by Cao Cao. Liu Zhang agreed and sent Fa Zheng as his envoy to contact Liu Bei. When Fa Zheng met Liu Bei, he secretly told him, "General, with your brilliance, you can overcome our incompetent and weak Governor Liu. Zhang Song, as a trusted adviser (of Liu Zhang), will serve as your spy. Upon acquiring Yi Province's wealth and resources, and having its natural barriers as protection, you can easily realise your grand ambitions."(後因璋聞曹公欲遣將征張魯之有懼心也，松遂說璋宜迎先主，使之討魯，復令正銜命。正旣宣旨，陰獻策於先主曰：「以明將軍之英才，乘劉牧之懦弱；張松，州之股肱，以響應於內；然後資益州之殷富，馮天府之險阻，以此成業，猶反掌也。」) Sanguozhi vol. 37. Fa Zheng also saw Liu Bei's marital problems and advised him to have Lady Sun sent back to Wu.(孫夫人才捷剛猛，有諸兄風。侍婢百人先主每下車，心常凜凜。正勸先主還之。) Huayang Guo Zhi vol. 6. Liu Bei accepted Fa Zheng's former advice and led his forces into Yi Province, where he met Liu Zhang at Fu County (涪縣; present-day Fucheng District, Mianyang, Sichuan). Liu Bei then led his troops north to Jiameng (葭萌; located about 20 km northeast of present-day Jiange County, Sichuan) before turning south to attack Liu Zhang later.(先主然之，泝江而西，與璋會涪。北至葭萌，南還取璋。) Sanguozhi vol. 37.
Helping Liu Bei seize Yi Province from Liu Zhang
Upon receiving news of Liu Bei's attack, Zheng Du (), an assistant officer from Guanghan Commandery (廣漢郡; around present-day Guanghan, Sichuan)(華陽國志曰：度，廣漢人，為州從事。) Huayang Guo Zhi annotation in Sanguozhi vol. 37. serving under Liu Zhang, pointed out to his lord that Liu Bei's army lacked supplies and was composed of newly recruited soldiers who might not be loyal to him. He suggested that Liu Zhang adopt a scorched earth policy against Liu Bei by forcing the residents of Baxi () and Zitong () commanderies to relocate elsewhere and destroy all the granaries and supply depots in the commanderies, and then fortify their defences while avoiding direct conflict with Liu Bei. He claimed that if this strategy was implemented, Liu Bei would run out of supplies within 100 days and retreat, and then Liu Zhang could attack him while he was retreating. Liu Bei felt frustrated when he heard about Zheng Du's plan and consulted Fa Zheng about it. Fa Zheng predicted that Liu Zhang would not heed Zheng Du's suggestion and was proven right: In response to Zheng Du's plan, Liu Zhang not only rejected it on the grounds that it would cause disturbance to the people, but also dismissed Zheng from office.(鄭度說璋曰：「左將軍縣軍襲我，兵不滿萬，士衆未附，野穀是資，軍無輜重。其計莫若盡驅巴西、梓潼民內涪水以西，其倉廩野穀一皆燒除，高壘深溝，靜以待之。彼至，請戰，勿許，乆無所資，不過百日，必將自走。走而擊之，則必禽耳。」先主聞而惡之，以問正。正曰：「終不能用，無可憂也。」璋果如正言，謂其羣下曰：「吾聞拒敵以安民，未聞動民以避敵也。」於是黜度，不用其計。) Sanguozhi vol. 37.
In 214,Zizhi Tongjian vol. 67. when Liu Bei's army surrounded Luocheng (), one of Liu Zhang's strongholds, Fa Zheng wrote a long letter to his former lord, pointing out that Liu Zhang was already in a highly disadvantageous position and urging him to give up resistance and surrender to Liu Bei.(及軍圍雒城，正牋與璋曰：「正受性無術， ... 以保尊門。」) Sanguozhi vol. 37.
Fa Zheng's letter was written as such:
Later that year, when Liu Bei's forces was besieging Yi Province's capital Chengdu, Xu Jing, a commandery Administrator serving under Liu Zhang, planned to surrender and defect to Liu Bei, but his plan was leaked out and hence aborted. Liu Zhang felt that he was already at the brink of destruction so he did not punish Xu Jing. He eventually surrendered and relinquished his control of Yi Province to Liu Bei. After taking over Yi Province, Liu Bei treated Xu Jing coldly because he felt that Xu was a disloyal person. Fa Zheng advised him, "Xu Jing is someone with an exaggerated reputation. However, my lord, you've recently built your foundation and you can't possibly explain the facts to everyone. Xu Jing's name is already well known throughout the Empire. If you don't treat him respectfully, others might think that you're belittling talented and virtuous people. You should honour and respect him, and make this known to everyone, just like how the King of Yan treated Guo Wei (郭隗)." Liu Bei followed Fa Zheng's advice and treated Xu Jing generously.(十九年，進圍成都，璋蜀郡太守許靖將踰城降，事覺，不果。璋以危亡在近，故不誅靖。璋旣稽服，先主以此薄靖不用也。正說曰：「天下有獲虛譽而無其實者，許靖是也。然今主公始創大業，天下之人不可戶說，靖之浮稱，播流四海，若其不禮，天下之人以是謂主公為賤賢也。宜加敬重，以眩遠近，追昔燕王之待郭隗。」先主於是乃厚待靖。) Sanguozhi vol. 37.
Sun Sheng criticizes Fa Zheng for his advice and the comparison between Guo Wei and Xu Jing :
Pei Songzhi completely disagrees with Sun Sheng's opinion:
Service under Liu Bei Becoming Liu Bei's Chief Adviser Liu Bei appointed Fa Zheng as the Administrator () of Shu Commandery () and General Who Spreads Martial Might (). Fa Zheng oversaw administrative affairs in the vicinity of Yi Province's capital Chengdu. While Zhuge Liang was promoted to administer internal affairs, Fa Zheng served as Liu Bei's chief adviser.(以正為蜀郡太守、揚武將軍，外統都畿，內為謀主。) Sanguozhi vol. 37.(先主復領益州牧，諸葛亮為股肱，法正為謀主，) Sanguozhi vol. 32.
Following Liu Bei's victory over Liu Zhang, his subordinates urged him to take for wife Liu Mao's widow. However Liu Bei refused on the basics that he and Liu Mao were of the same family. Fa Zheng then to convince him said: "In the ancient times, lady Huai Ying first married the Duke Huai of Jin and later married his own brother, the Duke Wen of Jin. If the marriage of a widow between brothers happened by the past then why not for you and Liu Mao who are not close kinsman?" Liu Bei agreed with him and married Lady Wu.(有志之士，無不競勸。群下勸先主納劉瑁妻。先主嫌其同族。法正曰：「論其親疏，何與晉文之於子圉乎？」從之。) Huayang Guo Zhi vol. 6.
During this period of time, Fa Zheng repaid all of his previous debts, good or bad. He would not forget those who showed him even a little kindness but also abused his power by taking revenge against those who offended him before. And by killing those who harmed him without the legal authority. Someone approached Zhuge Liang, another of Liu Bei's key advisers, and urged him to restrict Fa Zheng's influence by advising their lord to take action against him. However, Zhuge Liang replied, "When our lord was in Gong'an, he was wary of Cao Cao's influence in the north and fearful of Sun Quan's presence in the east. Even in home territory he was afraid that Lady Sun might stir up trouble. He was in such a difficult situation at the time that he could neither advance nor retreat. Fa Xiaozhi supported and helped him so much that he became his own wings (翼), such that he is now able to fly high and no longer remain under others' influence. How can we stop Fa Zheng from behaving as he wishes?" Zhuge Liang was aware that Liu Bei greatly favoured and trusted Fa Zheng, which was why he refused to intervene in this matter.(一飡之德，睚眦之怨，無不報復，擅殺毀傷己者數人。或謂諸葛亮曰：「法正於蜀郡太縱橫，將軍宜啟主公，抑其威福。」亮荅曰：「主公之在公安也，北畏曹公之彊，東憚孫權之逼，近則懼孫夫人生變於肘腋之下；當斯之時，進退狼跋，法孝直為之輔翼，令翻然翱翔，不可復制，如何禁止法正使不得行其意邪！」初，孫權以妹妻先主，妹才捷剛猛，有諸兄之風，侍婢百餘人，皆親執刀侍立，先主每入，衷心常凜凜；亮又知先主雅愛信正，故言如此。) Sanguozhi vol. 37.