The Battle of Tong Pass, also known as the Battle of Weinan, was fought between the warlord Cao Cao and a coalition of forces from Guanxi between April and November 211 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.
Background 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. 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.
In 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.(張魯據漢中，[建安十六年]三月，遣鍾繇討之。公使淵等出河東與繇會。) Sanguozhi, vol. 1; The month corresponds to 1 to 30 Apr 211 in the Julian calendar. 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.(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.
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 and rebelled against the Han imperial court.(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. The warlords included Hou Xuan (), Cheng Yin (), Yang Qiu, Li Kan (), Zhang Heng (), Liang Xing (), Cheng Yi (), and Ma Wan (). 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 () to avoid the war.
In response, Cao Cao sent Cao Ren against the coalition at Tong Pass (in present-day Tongguan County, Shaanxi) and gave strict orders to his generals to refrain from engaging the enemy.(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.
Crossing of the Wei River In late July or August 211, Cao Cao personally led an army against the rebels; he probably left 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 will make them unable to use their spears. Gentlemen, just watch."(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.
Upon reaching Tong Pass, Cao Cao ordered Xu Huang and Zhu Ling to lead their units across the Wei River via Puban Ford () at night and set up a camp on the west bank.(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. 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 (), 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!"(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.
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.(... 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.
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.(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. Ma Chao led his men to attack the walls but were repelled by Cao Cao's ambushes.
However, there have been 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.(或疑于時九月，水未應凍。) Cao Man Zhuan annotation in Sanguozhi vol. 1. 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.(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.
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.(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.
Han Sui had a meeting with Cao Cao later. Han Sui's father and Cao Cao were nominated as xiaolian (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 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.(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.
When Cao Cao was going to meet Han Sui again later, 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.(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.
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 dispatched 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.(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.
Aftermath
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.(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.
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.(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.
About a year after Ma Chao rebelled against the Han imperial court, Emperor Xian issued a decree ordering the execution of Ma Chao's family members in Ye.(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.
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, seized control of Jicheng () and forced Wei Kang's subordinates to submit to him. He took control of Liang Province.(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. 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.(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.