Battle of Tong Pass (211)
|Battle of Tong Pass|
|Part of the wars at the end of the Han dynasty|
The fictional duel between Xu Chu and Ma Chao, portrait at the Long Corridor of the Summer Palace, Beijing
|Cao Cao||Coalition of Guanxi forces|
|Commanders and leaders|
Li Kan †
Cheng Yi †
|60,000||100,000|
|Battle of Tong Pass|
|Battle of Weinan|
The Battle of Tong Pass, also known as the Battle of Weinan,[b] was fought between the warlord Cao Cao and a coalition of forces from Guanxi (west of Tong Pass) between April and November 211[a] in the late Eastern Han dynasty of China. The battle was initiated by Cao Cao's western expansion, which triggered uprisings in Guanxi. Cao Cao scored a decisive victory over the Guanxi coalition and established a hold of the Guanzhong region.
Towards the end of the Eastern Han dynasty, the warlord Ma Teng commanded a sizable army in the northwestern frontiers of China that threatened the North China Plain under the dominion of Cao Cao. When Cao Cao finished his unification of northern China in 207, he wished to turn south to attack the warlords Liu Bei and Sun Quan. To avoid a potential attack from behind, Cao Cao appointed Ma Teng as an official and summoned him to Ye (in present-day Handan, Hebei). Ma Teng and some of his family members were effectively held hostage to prevent Ma Teng's son, Ma Chao, from invading Cao Cao's territory.
Cao Cao's southern expedition failed and he was defeated by the combined forces of Sun Quan and Liu Bei at the Battle of Red Cliffs in 208. He turned his attention west instead and prepared to invade the Guanzhong region.
Around April 211, Cao Cao ordered Zhong Yao to lead an army against the warlord Zhang Lu in Hanzhong Commandery and sent Xiahou Yuan at the head of another force from Hedong Commandery to support Zhong Yao. Gao Rou cautioned Cao Cao against such a move, saying that sending troops west could draw suspicion from the warlords in the area and cause them to revolt.
The various warlords in the Guanzhong region feared that Cao Cao would to attack them because Zhong Yao's army would pass by the Guanzhong region on the way to Hanzhong Commandery. As soon as Zhong Yao's army entered Guanzhong, the warlords, under the leadership of Ma Chao and Han Sui, formed a coalition (known as the "Guanxi Coalition", or "coalition from the west of Tong Pass") and rebelled against the Han imperial court. The warlords included Hou Xuan (侯選), Cheng Yin (程銀), Yang Qiu, Li Kan (李堪), Zhang Heng (張橫), Liang Xing (梁興), Cheng Yi (成宜) and Ma Wan (馬玩). The coalition comprised a mixture of Han Chinese, Qiang and Hu soldiers. Many counties in the area joined the uprising. Some civilians escaped to Hanzhong via Ziwu Valley (子午谷) to avoid the war.
Crossing of the Wei River
In late July or August 211, Cao Cao personally led an army against the rebels, leaving behind his son Cao Pi to guard his base in Ye (in present-day Handan, Hebei). Some of his subordinates advised him: "The Guanxi soldiers are warlike and they specialise in using long spears. Only an elite vanguard force can stop them." Cao Cao replied: "I am in charge of the war, not the rebels. They may be skilled in using long spears, but I wll make them unable to use their spears. Gentlemen, just watch."
Upon reaching Tong Pass, Cao Cao ordered Xu Huang and Zhu Ling to lead their units across the Wei River via Puban Ford (蒲阪津) at night and set up a camp on the west bank. While Cao Cao and his men were preparing to cross the Wei River to the north bank, they suddenly came under attack by Ma Chao's forces, but Cao remained seated and refused to move. Zhang He and the other officers saw that the situation was very critical, so they led Cao Cao on board a ferry. As the river current was very strong, Cao Cao's vessels quickly sailed four or five li away from the south bank. Ma Chao ordered his troops to rain arrows upon the enemy boats. Ding Fei (丁斐), a colonel under Cao Cao, had released the cattle and horses to distract the enemy, so the Guanxi soldiers immediately gave up on attacking and started to seize whatever livestock they could lay their hands on. Cao Cao's officers were worried and panicky when they lost sight of their lord during the chaos, and they shed tears of joy when they reunited with him later. Cao Cao laughed and remarked: "I was almost trapped by that little scoundrel today!"
Construction of sand walls
After crossing the river, Cao Cao and his forces then headed south along the riverbank. The coalition retreated and made camp along the Wei River. Cao Cao set up many decoys to confuse the enemy while secretly sending troops to sail across the river and construct pontoon bridges. His forces crossed the river that night and built camps on the south bank. On the same night, the coalition attacked but were driven back by ambush forces deployed earlier by Cao Cao. Ma Chao and his allies also garrisoned at the south bank and they sent a messenger to meet Cao Cao, requesting to give up the territories west of the river in exchange for peace, but Cao Cao refused.
In late October or November 211, Cao Cao's forces attempted to cross the Wei River again, but came under attack by Ma Chao and his cavalry each time they tried to cross. Their camps were not stable and they could not build ramparts because the terrain was too sandy. Lou Gui suggested to Cao Cao: "The weather is cold. We can mix sand with water and use the mixture to construct walls. They will be ready after one night." Cao Cao heeded Lou Gui's suggestion and ordered his troops to work through the night to build the walls, which were ready by the following day. Cao Cao and his forces were hence able to cross the Wei River while the enemy was kept at bay by the walls. Ma Chao led his men to attack the walls but were repelled by Cao Cao's ambushes.
However, there were suspicions that the building of the sand walls did not actually occur, because the incident took place in late autumn or early winter (late October to November) and the weather was probably not cold enough to cause water to freeze. The fifth-century historian Pei Songzhi commented that the Wei Shu stated that Cao Cao's army reached Tong Pass in late August or September 211, and crossed the Wei River to the north bank in late September or October. The weather could not possibly be that cold in late autumn (late September to October) to cause water to freeze.
Cao Cao sowing discord between the coalition members
Ma Chao and the coalition repeatedly challenged Cao Cao to come out and engage them in battle but Cao ignored them. The rebels then offered to cede territories and send a hostage to Cao Cao's side in exchange for peace. As suggested by Jia Xu, Cao Cao pretended to agree to accept their offer.
Han Sui had a meeting with Cao Cao later. Han Sui's father and Cao Cao were nominated as xiaolians (civil service candidates) in the same year, while Cao and Han were also former colleagues when they were working in the old capital Luoyang. When they met at close quarters (they were on horseback and their steeds were side by side but facing opposite directions), they spoke nothing about military affairs and had a mere lighthearted conversation about old times. When Han Sui returned to his camp later, Ma Chao asked him: "What did Cao Cao say?" Han Sui replied: "Nothing." Ma Chao and the others became suspicious of Han Sui.
When Cao Cao was going to meet Han Sui again later (the other coalition members were with Han this time), his subordinates cautioned him: "My lord, when you meet the rebels, you may not be able to leave easily. How about using wooden horses as barriers?" Cao Cao agreed to their suggestion and spoke to Han Sui and his allies from behind the barriers. The coalition members greeted Cao Cao when they met him while their soldiers pushed their way forward to get a closer look at him. Cao Cao laughed and said: "You wish to see how I look like? I am also an ordinary person. I don't have four eyes or two mouths, but I am more intelligent." Cao Cao had brought along 5,000 armoured horsemen and instructed them to arrange themselves in an impressive formation. The rebel forces were shocked when they saw this display of military might by Cao Cao.
Some days later, Cao Cao wrote a letter to Han Sui which contained several "amendments", making it seem as though the recipient had deliberately edited the letter's contents to cover up something. Ma Chao and the others became even more suspicious of Han Sui after they saw the letter. In the meantime, Cao Cao was preparing for war with the coalition. He sent lightly armed troops to attack first, and then despatched his elite cavalry to launch a pincer attack. Cao Cao scored a major victory over the coalition: Cheng Yi, Li Kan and others were killed in action; Yang Qiu fled to Anding Commandery (安定郡; around present-day Pingliang, Gansu); Ma Chao and Han Sui retreated back to Liang Province. The Guanzhong region was pacified.
In late November or December 211, Cao Cao led an army from Chang'an to attack Yang Qiu and his forces besieged Anding Commandery (安定郡; around present-day Pingliang, Gansu). Yang Qiu surrendered and was allowed to retain his former titles and remain in his domain to pacify the people there.
Ma Chao retreated further west after his defeat at Tong Pass. Cao Cao pursued him to Anding Commandery but gave up on the pursuit after two months and headed back to Ye (in present-day Handan, Hebei) upon receiving news about unrest in northern China. He left Xiahou Yuan behind to defend Chang'an.
After Cao Cao left, Ma Chao led the various tribes in the region to attack the commanderies and counties in Guanzhong, while the people responded to his call and joined him in the revolt. In 213, Ma Chao killed Wei Kang, the Inspector of Liang Province, and seized control of Jicheng (兾城) and forced Wei Kang's subordinates to submit to him. He took control of Liang Province. Wei Kang's former subordinates were unhappy with Ma Chao so they plotted to get rid of him. Later that year, they rebelled against him and succeeded in driving him out of Guanzhong.
Ma Chao fled to Hanzhong, where he borrowed troops from the warlord Zhang Lu, and returned to attack those who drove him out of Guanzhong. He besieged Jiang Xu, Zhao Ang and their allies at Mount Qi (祁山; the mountainous areas around present-day Li County, Gansu) for about 30 days until reinforcements led by Cao Cao's generals Xiahou Yuan and Zhang He showed up and lifted the siege.
Cao Cao's analysis of the battle
After the battle, Cao Cao's officers asked their lord: "Earlier on, when the rebels were at Tong Pass, the north of the Wei River was not guarded. Why didn't you attack Pingyi (馮翊) from the east bank, and instead choose to defend Tong Pass and cross the river later?" Cao Cao replied, "The rebels were at Tong Pass. If I went to the east bank, they would definitely increase their defences at the fords and we wouldn't be able to cross over to the west. Hence, I chose to deploy our forces at Tong Pass so that the rebels would concentrate their defences on the south bank and lower their guard in the west. This was why our two generals (Xu Huang and Zhu Ling) were able to capture the west bank first, after which our main army crossed over to the north bank. The rebels were unable to fight for control of the west bank with us because our two generals had already occupied the area. When I gave orders for our carts to be linked together, wooden fences to be erected as defensive structures, and for our army to head south along the riverbank, I knew that we couldn't win then so I decided to display our weakness to the enemy. When we crossed the river back to the south bank and built solid walls, I didn't allow our men to engage the enemy because I wanted the enemy to become overconfident. As such, the rebels didn't attack our walls and instead requested to cede territories in exchange for peace. I pretended to agree so that they would be at ease and would not be on guard while our troops prepared for battle. When we attacked, it was indeed a case of 'a sudden crash of thunder leaves no time for one to cover his ears'. There are more than one way to how the situation on a battlefield can change."
Earlier on, during the battle, whenever Cao Cao received news of the arrival of enemy forces, he would express joy. After the battle, his officers asked him why, to which he replied: "Guanzhong is a very vast area. If the rebels garrisoned at the various strategic locations and we attack (all those places one by one), it would take a year or two to defeat all of them. However, they gathered (at Tong Pass) instead. They may have had superiority in numbers, but they were very disunited and they lacked a suitable leader, so they could be defeated in one strike. I was happy because it turned out to be much easier (than I expected)."
In Romance of the Three Kingdoms
The battle was mentioned in Chapters 58–59 of the 14th-century historical novel Romance of the Three Kingdoms (Sanguo Yanyi).
Ma Chao rallied an army to attack Cao Cao in revenge after Cao murdered his father Ma Teng and younger brothers Ma Xiu and Ma Tie.
Cao Cao was defeated by Ma Chao in the first skirmish of the battle. In the midst of the chaos, Cao Cao fled and was pursued by Ma Chao. Ma Chao shouted that the man dressed in the red robe was Cao Cao, so Cao took off his robe and discarded it to avoid being recognised. When Ma Chao saw that he shouted again that the man with a long beard was Cao Cao, so Cao drew his sword and quickly trimmed his beard until it was very short. Ma Chao then shouted that the man with a short beard was Cao Cao, and Cao responded by wrapping a flag around his jaw. Cao Hong appeared and held off Ma Chao long enough for Cao Cao to escape.
The following day, Ma Chao engaged Cao Cao's general Xu Chu in a duel. Xu Chu removed his upper garments, fighting topless against Ma Chao both on horseback and on foot. Neither of them managed to overcome his opponent.
Cao Cao eventually followed Jia Xu's strategy to turn Ma Chao and his ally Han Sui against each other. Ma Chao fell for the ruse and believed that Han Sui was planning to betray him so he barged into Han Sui's tent and attacked him. Han Sui lost his left arm during the fight and narrowly escaped under the protection of his subordinates. Cao Cao then took advantage of their internal conflict to attack them and defeated Ma Chao. Ma Chao fled to join the warlord Zhang Lu in Hanzhong after his defeat.
Both Ma Chao and Cao Cao's biographies in the Sanguozhi confirmed that Ma Chao started a rebellion in 211 together with Han Sui, Yang Qiu, Li Kan and Cheng Yi in Guanzhong and they formed a coalition army to attack Cao Cao, leading to the Battle of Tong Pass. The Dianlue stated that around a year after Ma Chao rebelled, Emperor Xian issued an imperial decree to Cao Cao, ordering him to have Ma Chao's entire family executed. This proves that the order of events had been reversed in Sanguo Yanyi, because Ma Chao started a rebellion in the first place, and then his clan was exterminated by Cao Cao about a year later.
The duel between Ma Chao and Xu Chu is not documented in the Sanguozhi and is likely to be fictional. Ma Chao, Cao Cao and Xu Chu's biographies gave an account of a meeting between Cao Cao, Ma Chao and Han Sui during the battle. Cao Cao rode forth on horseback to speak with Ma Chao and Han Sui. Cao Cao was accompanied only by Xu Chu. Ma Chao had confidence in himself and secretly harboured the intention of charging forward and capturing Cao Cao when they met. However, he had heard of Xu Chu before and suspected that the man with Cao Cao was Xu Chu. He then asked Cao Cao: "Where is your Tiger Marquis?" Cao Cao pointed at Xu Chu, and Xu glared at Ma Chao. Ma Chao was afraid and did not dare to make his move.
Ma Chao, Cao Cao and Jia Xu's biographies all mentioned Cao Cao heeding Jia Xu's suggestion to sow discord between Ma Chao and Han Sui and turn them against each other. Cao Cao's biography gave a detailed account of this incident, which is mainly similar to the description in Sanguo Yanyi, except that there is no mention about Ma Chao cutting off Han Sui's arm in a fight. Besides, the generals Cheng Yi, Li Kan, Yang Qiu and others were not subordinates of Han Sui, but rather, independent members who joined Ma Chao's alliance.
In popular culture
The Battle of Tong Pass is one of the playable stages in Koei's video game series Dynasty Warriors for the PS2. If the player is on Cao Cao's side and follows the order of events in both history and the novel by making Han Sui defect, it is an easy victory. In the original releases of Dynasty Warriors 6 for the PS3 and the Xbox 360 the stage was removed, but the stage was brought back, along with the Battle of Ruxukou and the Battle of Jieting, in the later release for the PS2.
- The Zizhi Tongjian recorded that the Battle of Tong Pass took place between the third and ninth months of the 16th year of the Jian'an era of the reign of Emperor Xian of the Eastern Han dynasty. This period corresponds to 1 April to 22 November 211 in the Gregorian calendar.
- "Weinan" means "south of the Wei (River)". Much of the fighting in the battle took place at the southern bank of the Wei River.
- Sima (1084), vol. 66.
- (張魯據漢中，三月，遣鍾繇討之。公使淵等出河東與繇會。) Sanguozhi vol. 1.
- (太祖欲遣鍾繇等討張魯，柔諫，以為今猥遣大兵，西有韓遂、馬超，謂為己舉，將相扇動作逆，宜先招集三輔，三輔苟平，漢中可傳檄而定也。繇入關，遂、超等果反。) Sanguozhi vol. 24.
- (是時關中諸將疑繇欲自襲，馬超遂與韓遂、楊秋、李堪、成宜等叛。) Sanguozhi vol. 1.
- (遣曹仁討之。超等屯潼關，公勑諸將：「關西兵精悍，堅壁勿與戰。」) Sanguozhi vol. 1.
- (魏書曰：議者多言「關西兵彊，習長矛，非精選前鋒，則不可以當也」。公謂諸將曰：「戰在我，非在賊也。賊雖習長矛，將使不得以刺，諸君但觀之耳。」) Wei Shu annotation in Sanguozhi vol. 1.
- (秋七月，公西征，與超等夾關而軍。公急持之，而潛遣徐晃、朱靈等夜渡蒲阪津，據河西為營。) Sanguozhi vol. 1.
- (公自潼關北渡，未濟，超赴船急戰。校尉丁斐因放牛馬以餌賊，賊亂取牛馬，公乃得渡， ...) Sanguozhi vol. 1.
- (曹瞞傳曰：公將過河，前隊適渡，超等奄至，公猶坐胡牀不起。張郃等見事急，共引公入船。河水急，北渡，流四五里，超等騎追射之，矢下如雨。諸將見軍敗，不知公所在，皆惶懼，至見，乃悲喜，或流涕。公大笑曰：「今日幾為小賊所困乎！」) Cao Man Zhuan annotation in Sanguozhi vol. 1.
- (... 循河為甬道而南。賊退，拒渭口，公乃多設疑兵，潛以舟載兵入渭，為浮橋，夜，分兵結營於渭南。賊夜攻營，伏兵擊破之。超等屯渭南，遣信求割河以西請和，公不許。) Sanguozhi vol. 1.
- (曹瞞傳曰：時公軍每渡渭，輒為超騎所衝突，營不得立，地又多沙，不可築壘。婁子伯說公曰：「今天寒，可起沙為城，以水灌之，可一夜而成。」公從之，乃多作縑囊以運水，夜渡兵作城，比明，城立，由是公軍盡得渡渭。) Cao Man Zhuan annotation in Sanguozhi vol. 1.
- de Crespigny (2010), p. 298.
- (或疑于時九月，水未應凍。) Cao Man Zhuan annotation in Sanguozhi vol. 1.
- (臣松之案魏書：公軍八月至潼關，閏月北渡河，則其年閏八月也，至此容可大寒邪！) Pei Songzhi's annotation in Sanguozhi vol. 1.
- (九月，進軍渡渭。 ... 超等數挑戰，又不許；固請割地，求送任子，公用賈詡計，偽許之。) Sanguozhi vol. 1.
- (韓遂請與公相見，公與遂父同歲孝廉，又與遂同時儕輩，於是交馬語移時，不及軍事，但說京都舊故，拊手歡笑。旣罷，超等問遂：「公何言？」遂曰：「無所言也。」超等疑之。) Sanguozhi vol. 1.
- (魏書曰：公後日復與遂等會語，諸將曰：「公與虜交語，不宜輕脫，可為木行馬以為防遏。」公然之。賊將見公，悉於馬上拜，秦、胡觀者，前後重沓，公笑謂賊曰：「爾欲觀曹公邪？亦猶人也，非有四目兩口，但多智耳！」胡前後大觀。又列鐵騎五千為十重陣，精光耀日，賊益震懼。) Wei Shu annotation in Sanguozhi vol. 1.
- (他日，公又與遂書，多所點竄，如遂改定者；超等愈疑遂。公乃與克日會戰，先以輕兵挑之，戰良乆，乃縱虎騎夾擊，大破之，斬成宜、李堪等。遂、超等走涼州，楊秋奔安定，關中平。) Sanguozhi vol. 1.
- (冬十月，軍自長安北征楊秋，圍安定。秋降，復其爵位，使留撫其民人。) Sanguozhi vol. 1.
- (十二月，自安定還，留夏侯淵屯長安。) Sanguozhi vol. 1.
- (超走保諸戎，曹公追至安定，會北方有事，引軍東還。) Sanguozhi vol. 36.
- (超至安定，遂奔涼州。詔收滅超家屬。超復敗於隴上。) Dianlue annotation in Sanguozhi vol. 36.
- (超果率諸戎以擊隴上郡縣，隴上郡縣皆應之，殺涼州刺史韋康，據兾城，有其衆。超自稱征西將軍，領并州牧，督涼州軍事。) Sanguozhi vol. 36.
- (康故吏民楊阜、姜叙、梁寬、趙衢等合謀擊超。阜、叙起於鹵城，超出攻之，不能下；寬、衢閉兾城門，超不得入。) Sanguozhi vol. 36.
- (超奔漢中，還圍祁山。叙等急求救，諸將議者欲須太祖節度。淵曰：「公在鄴，反覆四千里，比報，叙等必敗，非救急也。」遂行，使張郃督步騎五千在前，從陳倉狹道入，淵自督糧在後。郃至渭水上，超將氐羌數千逆郃。未戰，超走，郃進軍收超軍器械。淵到，諸縣皆已降。) Sanguozhi vol. 9.
- (遂共閉門逐超，超奔漢中，從張魯得兵還。異復與昂保祁山，為超所圍，三十日救兵到，乃解。超卒殺異子月。凡自兾城之難，至于祁山，昂出九奇，異輒參焉。) Lie Nü Zhuan annotation in Sanguozhi vol. 25.
- (諸將或問公曰：「初，賊守潼關，渭北道缺，不從河東擊馮翊而反守潼關，引日而後北渡，何也？」公曰：「賊守潼關，若吾入河東，賊必引守諸津，則西河未可渡，吾故盛兵向潼關；賊悉衆南守，西河之備虛，故二將得擅取西河；然後引軍北渡，賊不能與吾爭西河者，以有二將之軍也。連車樹柵，為甬道而南，旣為不可勝，且以示弱。渡渭為堅壘，虜至不出，所以驕之也；故賊不為營壘而求割地。吾順言許之，所以從其意，使自安而不為備，因畜士卒之力，一旦擊之，所謂疾雷不及掩耳，兵之變化，固非一道也。」) Sanguozhi vol. 1.
- (始，賊每一部到，公輒有喜色。賊破之後，諸將問其故。公荅曰：「關中長遠，若賊各依險阻，征之，不一二年不可定也。今皆來集，其衆雖多，莫相歸服，軍無適主，一舉可滅，為功差易，吾是以喜。」) Sanguozhi vol. 1.
- (超既統眾，遂與韓遂合從，及楊秋、李堪、成宜等相結，進軍至潼關。) Sanguozhi vol. 36.
- (是時關中諸將疑繇欲自襲，馬超遂與韓遂、楊秋、李堪、成宜等叛。) Sanguozhi vol. 1.
- (詔收滅超家屬。) Dianlue annotation in Sanguozhi vol. 36.
- (曹公與遂、超單馬會語，超負其多力，陰欲突前捉曹公，曹公左右將許褚瞋目盻之，超乃不敢動。) Sanguozhi vol. 36.
- (曹公與遂、超單馬會語，超負其多力，陰欲突前捉曹公，曹公左右將許褚瞋目盻之，超乃不敢動。) Sanguozhi vol. 1.
- (其後太祖與遂、超等單馬會語，左右皆不得從，唯將褚。超負其力，陰欲前突太祖，素聞褚勇，疑從騎是褚。乃問太祖曰：「公有虎侯者安在？」太祖顧指褚，褚瞋目盼之。超不敢動，乃各罷。) Sanguozhi vol. 18.
- (曹公用賈詡謀，離間超、遂，更相猜疑，軍以大敗。) Sanguozhi vol. 36.
- (超等數挑戰，又不許；固請割地，求送任子，公用賈詡計，偽許之。韓遂請與公相見，公與遂父同歲孝廉，又與遂同時儕輩，於是交馬語移時，不及軍事，但說京都舊故，拊手歡笑。既罷，超等問遂：「公何言？」遂曰：「無所言也。」超等疑之。他日，公又與遂書，多所點竄，如遂改定者；超等愈疑遂。公乃與克日會戰，先以輕兵挑之，戰良久，乃縱虎騎夾擊，大破之，斬成宜、李堪等。遂、超等走涼州，楊秋奔安定，關中平。) Sanguozhi vol. 1.
- (太祖後與韓遂、馬超戰於渭南，超等索割地以和，並求任子。詡以為可偽許之。又問詡計策，詡曰：「離之而已。」太祖曰：「解。」一承用詡謀。語在武紀。卒破遂、超，詡本謀也。) Sanguozhi vol. 10.
- Chen, Shou (3rd century). Records of the Three Kingdoms (Sanguozhi).
- de Crespigny, Rafe (2010). Imperial warlord: a biography of Cao Cao 155-220 AD. Leiden: Brill. ISBN 978-90-04-18522-7.
- Luo, Guanzhong (14th century). Romance of the Three Kingdoms (Sanguo Yanyi), ch. 58-59.
- Pei, Songzhi (5th century). Annotations to Records of the Three Kingdoms (Sanguozhi zhu).
- Sima, Guang (1084). Zizhi Tongjian.