Li Su

Biography

Family Background and Early Life

Li Su was born into one of the most distinguished military families of the mid-Tang period. His father, Li Sheng, was a renowned general of the restoration era who helped suppress the rebellion of Zhu Ci and recover Chang'an. For these achievements he was enfeoffed as Prince of Xiping Commandery and had his portrait placed in Lingyan Pavilion during Emperor Dezong's reign. Li Sheng had fifteen sons, of whom Li Su was the eleventh. Li Su's birth mother died early, and he was raised by Lady Wang, Duchess of Jin. When Lady Wang died, Li Sheng ordered Li Su to wear only the mourning dress prescribed for a more distant relation because she was not his birth mother. Li Su wept bitterly and insisted on observing the heavier mourning dress appropriate to a mother. Moved by his filial devotion, Li Sheng agreed. The Old Book of Tang records: “Su lost his birth mother early and was raised by Lady Wang, Duchess of Jin. When she died, Sheng, because she was not his principal wife, ordered him to wear the sima mourning dress. He cried and could not bear it; Sheng was moved and permitted him to wear the heavier mourning.” The episode was later cited as evidence of Li Su's filial devotion, strong temperament, and deep sense of personal loyalty.

Li Su entered official service through hereditary privilege and was first appointed Pitch Regulator of the Court of Imperial Sacrifices, later becoming Vice Director of the Court of Imperial Guards. In 793, the ninth year of Zhenyuan, Li Sheng died. Li Su and his elder brother Li Xian built a hut beside the tomb and observed mourning there. Emperor Dezong feared that their grief would damage their health and ordered them to return home. Li Su obeyed, spent one night at home, and then ran barefoot back to the tomb. Recognizing that his resolve could not be changed, Dezong allowed him to complete the full three-year mourning period. Contemporaries praised the episode, and it accorded with the style of sincere treatment and moral obligation that later characterized Li Su's relations with his soldiers.

Middle Career

After completing mourning, Li Su was appointed Right Junior Preceptor of the Heir Apparent. He later served as Director of the Court of the Imperial Treasury and Left Junior Preceptor of the Heir Apparent, and was sent out as prefect of Fang and Jin prefectures. His local administration was regarded as effective, and he received the rank of Grand Master for Splendid Happiness after strong performance evaluations. He later returned to court, again served in the heir apparent's establishment, and rose to Supervisor of the Household of the Crown Prince and Commissioner of Palace Gardens and Stables.

Li Su's middle career was steady but lacked major military accomplishments. Although he was a capable strategist and skilled horseman and archer, he spent many years in offices attached to the Eastern Palace or as a prefect and had few opportunities to demonstrate military ability. The relatively quiet period nevertheless tempered his character and deepened his understanding of the dangers posed by semi-independent regional military governments.

Commission to Suppress the Rebellion

In 814, the ninth year of Yuanhe, Wu Shaoyang, military commissioner of Huaixi, died. His son Wu Yuanji seized control of the army without authorization, and Emperor Xianzong of Tang resolved to suppress him by force. The war dragged on. In 816, the eleventh year of Yuanhe, Gao Xiayu, military commissioner of Tang and Deng, suffered a severe defeat at Tiecheng, and his successor Yuan Zi likewise failed to make progress after prolonged fighting. Tang morale on the western front collapsed, and the campaign against Huaixi reached a stalemate.

Li Su then submitted a memorial volunteering for frontline service. Chancellor Li Fengji also appreciated his abilities. In the twelfth lunar month of 816, Li Su was appointed Left Cavalier Attendant-in-Ordinary, concurrently prefect of Deng Prefecture and Censor-in-chief, and military commissioner of Sui, Tang, and Deng prefectures, replacing Yuan Zi and taking command of the western front.

After arriving, Li Su did not immediately tighten discipline or prepare for battle. He knew that the Tang forces had just been defeated and were demoralized, while the rebels had grown arrogant after repeatedly defeating Gao and Yuan. He therefore deliberately presented an appearance of weakness, refrained from imposing strict discipline, and told his soldiers: “The Son of Heaven knows that I am compassionate and can endure humiliation, and therefore ordered me to care for you. Fighting is not my business.” He dismissed female entertainers, held no banquets, and personally comforted wounded and sick troops. Because Li Su previously held no great military reputation and appeared to have no intention of preparing for battle, the rebels relaxed their vigilance and stopped strengthening their defenses.

Preparing the Huaixi Campaign

While presenting weakness outwardly, Li Su secretly planned a direct strike on Cai Prefecture. He treated surrendering soldiers generously and personally questioned every Huaixi deserter, gradually gaining detailed knowledge of enemy terrain, troop deployments, and weaknesses. In the second lunar month of 817, a patrol commanded by Ma Shaoliang captured Wu Yuanji's fierce general Ding Shiliang. Li Su's officers urged that Ding be executed, but Li Su saw that he showed no fear and praised him as “a true man,” personally releasing him from his bonds. Ding Shiliang was moved to tears and vowed to repay him with his life. He then proposed a plan that led to the capture of Chen Guangqia, principal adviser to Wu Xiulin, commander of Wencheng Stockade. In the third lunar month, Wu Xiulin surrendered with three thousand men. Li Su patted him on the back in reassurance, incorporated his troops, and employed his brave subordinate Li Xian, changing the man's name to Li Zhongyi.

Li Su asked Wu Xiulin how Cai Prefecture might be taken. Wu replied that victory required Li You, a brave and capable Huaixi cavalry commander who held Xingqiao Stockade and had repeatedly defeated government troops. Li Su arranged an ambush by sending Shi Yongcheng with three hundred cavalry to lure Li You into pursuit and capture him. Because Li You had killed and wounded many Tang soldiers, the army clamored for his execution. Li Su overruled them, released Li You from bonds, and treated him as an honored guest. Li Su held private discussions with Li You and Li Zhongyi, often until midnight, which made other officers suspect that Li You was secretly working for the enemy. Under pressure from the army, Li Su sent Li You in chains to the capital while secretly memorializing Emperor Xianzong: “If Li You is killed, there will be no way to achieve success.” Xianzong ordered Li You released. Li Su was delighted and appointed him commissioner of detached troops, later making him Commissioner of the Six Garrisons with command of three thousand elite troops of Shannan East Circuit. Grateful for Li Su's trust, Li You served with complete loyalty and became a key planner of the assault on Cai Prefecture.

Snowy-Night Attack on Cai Prefecture

In the ninth lunar month of 817, the twelfth year of Yuanhe, Li Su judged the time ripe and secretly submitted his plan for a surprise attack on Cai Prefecture to Chancellor Pei Du. Pei strongly approved and authorized the operation. On the tenth day of the tenth lunar month, amid wind and snow, Li Su sent three thousand men as the vanguard, personally led another three thousand in the center, and placed three thousand more in the rear. The army moved east in secrecy. The initial order merely instructed the troops to march sixty li east and capture Zhangchai Village, a strategic point about seventy li from Cai Prefecture. After taking the village and allowing a brief rest, Li Su revealed that the true objective was Cai Prefecture. His officers were terrified; even the army supervisor wept, believing that Li You had deceived them. The snowstorm tore the banners, men and horses froze to death along the road, and many soldiers believed they would not survive.

The Tang army forced a march of thirty-five kilometers and reached the walls of Cai Prefecture. Near the city was a pond filled with chickens and ducks. Li Su ordered his soldiers to disturb the birds so that their cries would mask the sound of the advancing army. Since Wu Shaoyang had first defied the court, no government army had reached the walls of Cai Prefecture for thirty years. Combined with the heavy snow, this left the defenders completely unprepared. Li Su and his officers led from the front, cut footholds into the city wall, climbed first, and killed sleeping guards, while leaving the night watchmen to continue sounding the watches as usual. Wu Yuanji initially refused to believe that government troops had entered the city and assumed that prisoners were rioting. When he finally confirmed the truth, he was shocked, withdrew with his attendants into the headquarters citadel, and sent men to Huiqu for aid.

After entering the city, Li Su treated the family of Dong Chongzhi, commander at Huiqu, with generosity and sent Dong's son to summon him to surrender. Meanwhile, Li Su intensified the attack on the citadel. Wu Yuanji had lost local support, and townspeople competed to help the Tang troops carry firewood to burn the gates. On the twelfth day of the tenth lunar month, the citadel fell. Wu Yuanji surrendered and was transported to the capital in a cage. More than twenty thousand troops in Shen and Guang prefectures surrendered at the same time. The Huaixi Rebellion was ended.

Later Years

After the pacification of Huaixi, Li Su was appointed Acting Left Vice Director of the Department of State Affairs, concurrently military commissioner of Shannan East Circuit, and enfeoffed as Duke of Liang. In 818, the thirteenth year of Yuanhe, he was transferred as Military Commissioner of Wuning and joined the campaign against the rebellious Pinglu military governor Li Shidao. At Jinxiang, Li Su inflicted a major defeat on Li Shidao's army and won repeated engagements, contributing to the suppression of the Ziqing rebellion.

In 820, the fifteenth year of Yuanhe, Emperor Xianzong died and Emperor Muzong succeeded. Li Su was appointed Chancellor with the designation Tong Pingzhangshi and military commissioner of Zhaoyi, and soon afterward was transferred to Weibo. In 821, the first year of Changqing, Tian Hongzheng, military commissioner of Chengde, was killed. Li Su wanted to raise troops to avenge him, but serious illness prevented him from doing so. He returned to Luoyang to recover and was appointed Junior Guardian of the Crown Prince. He died in the tenth lunar month of the same year at the age of forty-nine. The court posthumously granted him the office of Defender-in-chief and the posthumous name Wu. In 846, the sixth year of Huichang, he was granted sacrificial association in the Temple of King Wucheng.

Major Activities

Surprise Snowy-Night Attack on Cai Prefecture

The greatest achievement of Li Su's career was his snowy-night attack on Cai Prefecture. In the tenth lunar month of 817, the twelfth year of Yuanhe, he used the cover of a snowstorm to lead nine thousand elite troops on a long forced march, seized the Huaixi capital of Cai Prefecture in a single stroke, captured Wu Yuanji alive, and ended the four-year Huaixi Rebellion. The campaign became a classic example of surprise attack in Chinese military history and displayed Li Su's strategy, courage, and ability to use men. Three factors were central to the success: he spent a long period deliberately appearing weak so that the defenders of Cai Prefecture relaxed their vigilance; he treated surrendered officers generously and thereby acquired accurate intelligence on Huaixi; and he maintained strict secrecy, to the point that even his own soldiers did not know their destination during the march, preserving the operation's element of surprise.

Winning Over Surrendered Officers Through Trust

Li Su placed great emphasis on winning people over. He did not treat surrendered officers with suspicion, but showed them sincere trust. Ding Shiliang, Wu Xiulin, Li You, and Dong Chongzhi were all leading Huaixi officers who were captured by or surrendered to Li Su, and all were released from restraints, treated favorably, and entrusted with responsibility. Li You had been a Huaixi cavalry commander who repeatedly defeated government forces, and many Tang soldiers wanted him killed. Li Su alone overruled them and preserved his life. Li You, grateful for this recognition, became a central planner of the attack on Cai Prefecture. Dong Chongzhi commanded Huiqu and possessed substantial troops. After entering Cai Prefecture, Li Su treated Dong's family well, sent Dong's son to summon him to surrender, and promised to preserve his life. When Emperor Xianzong later wanted Dong executed, Li Su memorialized repeatedly on his behalf, and Dong was ultimately spared death and merely demoted. Li Su's sincerity toward former enemies enabled him to gain their wholehearted service and was a crucial reason for his military success.

Caring for Soldiers and Restoring Morale

When Li Su first arrived in Tang Prefecture, the Tang army on the western front had just been defeated and morale was low. He adopted several measures to stabilize the troops. He deliberately refrained from tightening discipline in order to mislead the enemy, while personally comforting wounded and sick soldiers, dismissing entertainers, and avoiding feasts. He also abolished a harsh standing order that required the families of people who harbored enemy spies to be slaughtered, instead treating captured spies generously. Some of those spies then provided intelligence to the Tang army. These measures restored morale among the Tang and Deng troops and created a strong desire to fight.

Further Service After Huaixi

After Huaixi was pacified, Li Su also participated in the campaign against the rebellious Pinglu military governor Li Shidao. In 818, as Military Commissioner of Wuning, he defeated Li Shidao's forces decisively at Jinxiang and continued to win subsequent engagements. He later served as military commissioner of Zhaoyi and Weibo and retained a formidable reputation among the regional commands.

Personal Relations

Family

• Father: Li Sheng, Prince of Xiping Commandery and a celebrated mid-Tang general
• Mother: died early; surname unknown
• Foster mother: Lady Wang, Duchess of Jin
• Elder brother: Li Xian, Li Sheng's eldest son; observed mourning at their father's tomb together with Li Su
• Elder brother: Li Yuan, military commissioner of Wuning; Li Su once took command of his forces
• Wife: Lady Wei, daughter of Princess Tang'an; married Li Su in 798, the fourteenth year of Zhenyuan
• Son: Li Pin, military commissioner of Fengxiang
• Daughter: Li Hong, Lady of Longxi County, married Xie Guan, prefect of Ci Prefecture

Friends and Colleagues

• Pei Du: chancellor and commissioner for pacification and suppression of Huaixi; supported Li Su's plan to attack Cai Prefecture
• Li Fengji: chancellor who recommended Li Su for command of Tang and Deng
• Han Yu: writer who composed the Stele Inscription on the Pacification of Huaixi; controversy arose because the inscription gave relatively little space to Li Su's achievements

Officers and Surrendered Commanders

• Ding Shiliang: fierce general under Wu Yuanji; after capture he surrendered to Li Su and proposed the plan that captured Chen Guangqia
• Wu Xiulin: commander of Wencheng Stockade; surrendered with his troops and proposed the strategy for taking Cai Prefecture
• Li You: Huaixi cavalry commander captured through Li Su's stratagem; appointed Commissioner of the Six Garrisons and became a principal planner of the Cai operation
• Li Zhongyi: originally named Li Xian, an officer under Wu Xiulin; renamed by Li Su and involved in the secret planning of the attack on Cai Prefecture
• Dong Chongzhi: commander of Huiqu; Li Su treated his family well, sent his son to summon him to surrender, and later worked to spare him from execution
• Shi Yongcheng: garrison aide who was ordered to conduct the ambush that captured Li You

Ruler–Minister Relations

• Emperor Xianzong of Tang, Li Chun: entrusted Li Su with suppressing the rebellion and supported his plan to strike Cai Prefecture
• Emperor Dezong of Tang, Li Shi: allowed Li Su to complete the full mourning period for his father
• Emperor Muzong of Tang, Li Heng: ruler served by Li Su late in life; appointed him to Zhaoyi and Weibo

Enemies

• Wu Yuanji: rebellious military governor of Huaixi, captured alive by Li Su
• Li Shidao: rebellious military governor of Pinglu; Li Su campaigned against him and decisively defeated his army at Jinxiang

Historical Assessment

Tang and Contemporary Assessments

• Emperor Xianzong strongly praised Li Su's achievement at Cai Prefecture. After the victory, Li Su was appointed Acting Left Vice Director of the Department of State Affairs, military commissioner of Shannan East Circuit, and Duke of Liang. Xianzong also specially ordered Han Yu to compose the Stele Inscription on the Pacification of Huaixi to commemorate the campaign.
• Chancellor Pei Du “greatly approved” Li Su's surprise-attack plan and authorized the operation, showing the high assessment of his military abilities among senior court officials.
• Although Han Yu's Stele Inscription on the Pacification of Huaixi placed Pei Du's contribution first, it described Li Su's surprise advance in the words “the western army leapt forward; none remained along the road,” acknowledging the speed and success of his campaign.
• Li Su's officer Shi Xiaozhong was angered that the inscription gave too little credit to Li Su and pushed over the stele. The incident reached Emperor Xianzong, who eventually ordered Duan Wenchang to rewrite the inscription. The episode itself reflected contemporary recognition of Li Su's military contribution.

Song and Yuan Periods

• The Northern Song general Yue Fei is said to have commented on Li Su's snowy-night attack on Cai Prefecture and greatly admired his use of surprise.
• The Northern Song official compilation Biographies of One Hundred Generals from the Seventeen Histories included Li Su among its hundred generals, placing him alongside renowned commanders of earlier periods.
• The historian's assessment in the Old Book of Tang praised Li Su as “calmly courageous and long in calculation, sincere in dealing with his officers, and therefore able, from a position of weakness, to emerge where the enemy did not expect him.”
• The New Book of Tang stated that in “pacifying Huaixi, his merit was first,” explicitly giving him the leading place among the military achievements of the Yuanhe campaigns.

Ming and Qing Periods

• Wang Fuzhi, discussing the Huaixi campaign in Du Tongjian Lun, held that the success of the snowy-night attack lay in Li Su's ability “to endure” and “to decide,” praising his strategic judgment.
• Zhao Yi's Notes on the Twenty-Two Histories, in discussing Tang regional military disorders, treated the pacification of Huaixi as a decisive turning point in Emperor Xianzong's campaigns and remarked that “once Huaixi was pacified, the military governors lost courage.”
• Wang Mingsheng's Shiqishi Shangque examined Li Su's achievements and argued that they were no less than Pei Du's, correcting what he regarded as the Stele Inscription on the Pacification of Huaixi's excessive emphasis on the chancellor at the expense of the general.

Modern Assessments

• Cen Zhongmian's History of the Sui and Tang described Li Su's snowy-night attack on Cai Prefecture as “one of the most brilliant pages in Tang military history,” emphasizing its exemplary use of surprise.
• Huang Yongnian, in Political History of China from the Sixth to Ninth Centuries, argued that Li Su succeeded because he “treated officers sincerely and made good use of surrendered men,” making the campaign a classic example of combining political methods with military action in Tang warfare against regional commands.
• Modern studies of military history often list the snowy-night attack on Cai Prefecture as a classic ancient Chinese surprise operation, alongside Han Xin's last-stand battle and Li Jing's night attack on the Yin Mountains.