|Prince of Zhongshan (中山王)|
|Tenure||232 – 1 November 235|
|Prince of Puyang (濮陽王)|
|Tenure||226 – 232|
|Prince of Zan (贊王)|
|Reign||223 – 226|
|Prince of Beihai (北海王)|
|Tenure||222 – 223|
|Died||1 November 235|
|House||House of Cao|
Early life under the Han dynasty
Cao Gun was a son of Cao Cao, a warlord who rose to prominence towards the end of the Han dynasty and laid the foundation for the Cao Wei state. His mother was Lady Du (杜夫人), a concubine of Cao Cao. She also bore Cao Lin.
Cao Gun was enfeoffed as the "Marquis of Ping District" (平鄉侯) in 216 by Emperor Xian, the figurehead emperor of the Han dynasty. As a youth, he was known for being studious and diligent. He could already write essays when he was about nine years old. Every time when he was reading and writing, his attendants were worried that he would stress himself out and fall sick, so they advised him to rest more. However, Cao Gun continued to read and write tirelessly because he enjoyed doing so. In 217, Emperor Xian changed Cao Gun's title first to "Marquis of Dong District" (東鄉侯) and later to "Marquis of Zan" (贊侯).
Life during Cao Pi's reign
In 220, following Cao Cao's death, Cao Gun's half-brother Cao Pi usurped the throne from Emperor Xian, ended the Han dynasty, and established the Cao Wei state with himself as the new emperor. He enfeoffed Cao Gun as a duke in the following year. When some officials congratulated him on becoming a duke, Cao Gun said, "I've lived in the palace my whole life so I don't understand the hardships faced by the common people and mistakes caused by arrogance and oversight. I hope that you, gentlemen, can also point out my weaknesses apart from simply congratulating me."
While his brothers indulged in fun and entertainment, Cao Gun was often seen reading and being in deep thought. The officials around Cao Gun discussed among themselves and said, "His Majesty (Cao Pi) has ordered us to observe the Duke's behaviour. It's our duty to report to His Majesty when we see the Duke behaving inappropriately. However, when we see the Duke doing good deeds, we should also praise him in front of His Majesty." They then wrote a memo to Cao Pi to praise Cao Gun. Cao Gun was shocked when he heard about it and he scolded the officials, "It is one's responsibility to conduct himself with virtue and faithfully perform his duties. There's no need to tell anyone. Now that you've informed His Majesty, I feel more pressured and burdened. Besides, if one behaves well and does good deeds, why does he need to worry that no one will know? What you've done is not helpful to me." Such was Cao Gun's humility.
In 222, Cao Pi elevated Cao Gun from the status of a duke to a prince under the title "Prince of Beihai" (北海王). In the same year, when a yellow dragon was allegedly sighted in the Zhang River (漳水) to the west of Ye (around present-day Handan, Hebei), Cao Gun thought that it was an auspicious sign so he wrote a memorial to Cao Pi to praise the emperor. Cao Pi was so pleased that he rewarded Cao Gun with 10 jin of gold and issued an imperial decree to thank Cao Gun and praise him in return.
In 223, Cao Pi changed Cao Gun's title to "Prince of Zan" (贊王). He changed it again in 226 to "Prince of Puyang" (濮陽王).
Life during Cao Rui's reign
Cao Gun settled in his princedom in Puyang County in 228 during the reign of Cao Rui, Cao Pi's son and successor. He was known for being frugal and thrifty. Instead of purchasing cloth from the market, he instructed his wife and concubines to weave at home. That became a daily activity in his household.
In 233, someone reported to the imperial court that Cao Gun had violated a curfew by walking on the streets at night when he visited Luoyang in the winter of 231. Cao Rui knew that Cao Gun had a reputation for his virtuous and good behaviour, so he wanted to overlook this transgression and issue only an official warning to Cao Gun. However, after some officials pressured him, Cao Rui decided to punish Cao Gun by removing two counties, with a total of 750 taxable households, from his princedom. Cao Gun felt so distressed and upset that he instructed his subordinates to be more mindful in the future. Cao Rui appreciated Cao Gun's expression of remorse, so he returned the two counties to Cao Gun in the following year.
In the autumn of 235, when Cao Gun fell sick, Cao Rui sent a palace physician to treat him, ordered his palace attendants to bring him various health products, and even instructed Cao Gun's mother Lady Du and brother Cao Lin to visit him. As Cao Gun's condition worsened, he maintained the same humility he showed throughout his life by saying that he was undeserving of such generosity from the emperor. Although he knew that his funeral had to be in accordance with Confucian traditions, he requested for a simple funeral and to be buried near the tomb of Quyuan (蘧瑗), a famous official from the Wey state in the Spring and Autumn period. Before his death, he told Cao Fu (曹孚), his son and heir apparent, to conduct himself with humility and virtue, to empathise with his subordinates and the common people, to respect his grandmother Lady Du and uncle Cao Lin, and to learn how to be a loyal and faithful subject of the emperor.
Cao Gun died on 1 November 235[a] and was honoured with the posthumous title "Prince Gong" (恭王). After Cao Gun's death, Cao Rui ordered Cao Gun's brother, Cao Lin, to oversee the funeral arrangements and sent his Minister Herald (大鴻臚) to attend the funeral and read a eulogy. Throughout his life, Cao Gun produced over 20,000 pieces of writing. Although he was not as talented as his half-brother Cao Zhi in literary arts, his passion for reading and writing equalled Cao Zhi's.
Cao Gun's son, Cao Fu (曹孚), succeeded him and became the next Prince of Zhongshan. Throughout the reigns of the subsequent Wei emperors, the number of taxable households in Cao Fu's princedom increased until it reached 3,400 in the reign of Cao Huan.
- ([青龍三年]冬十月己酉，中山王衮薨。) Sanguozhi vol. 3.
- (武皇帝二十五男： ... 杜夫人生沛穆王林、中山恭王衮， ...) Sanguozhi vol. 20.
- (中山恭王衮，建安二十一年封平鄉侯。少好學，年十餘歲能屬文。每讀書，文學左右常恐以精力為病，數諫止之，然性所樂，不能廢也。) Sanguozhi vol. 20.
- (二十二年，徙封東鄉侯，其年又改封贊侯。) Sanguozhi vol. 20.
- (黃初二年，進爵為公，官屬皆賀，衮曰：「夫生深宮之中，不知稼穡之艱難，多驕逸之失。諸賢旣慶其休，宜輔其闕。」) Sanguozhi vol. 20.
- (每兄弟游娛，衮獨譚思經典。文學防輔相與言曰：「受詔察公舉錯，有過當奏，及有善，亦宜以聞，不可匿其美也。」遂共表稱陳衮美。衮聞之，大驚懼，責讓文學曰：「脩身自守，常人之行耳，而諸君乃以上聞，是適所以增其負累也。且如有善，何患不聞，而遽共如是，是非益我者。」其誡慎如此。) Sanguozhi vol. 20.
- (三年，為北海王。其年，黃龍見鄴西漳水，衮上書贊頌。詔賜黃金十斤，詔曰：「昔唐叔歸禾，東平獻頌，斯皆骨肉贊美，以彰懿親。王研精墳典，耽味道真，文雅煥炳，朕甚嘉之。王其克慎明德，以終令問。」) Sanguozhi vol. 20.
- (四年，改封贊王。七年，徙封濮陽。) Sanguozhi vol. 20.
- (太和二年就國���尚約儉，教勑妃妾紡績織絍，習為家人之事。) Sanguozhi vol. 20.
- (五年冬，入朝。六年，改封中山。) Sanguozhi vol. 20.
- (初，衮來朝，犯京都禁。青龍元年，有司奏衮。詔曰：「王素敬慎，邂逅至此，其以議親之典議之。」有司固執。詔削縣二，戶七百五十。) Sanguozhi vol. 20.
- (魏書載璽書曰：「制詔中山王：有司奏，王乃者來朝，犯交通京師之禁。朕惟親親之恩，用寢吏議。然法者，所與天下共也，不可得廢。今削王縣二，戶七百五十。夫克己復禮，聖人稱仁，朝過夕改，君子與之。王其戒諸，無貳咎悔也。」) Wei Shu annotation in Sanguozhi vol. 20.
- (衮憂懼，戒勑官屬愈謹。帝嘉其意，二年，復所削縣。) Sanguozhi vol. 20.
- (三年秋，衮得疾病，詔遣太醫視疾，殿中、虎賁齎手詔、賜珍膳相屬，又遣太妃、沛王林並就省疾。衮疾困，勑令官屬曰：「吾寡德忝寵，大命將盡。吾旣好儉， ... 」 ... 又令世子曰：「汝幼少，未聞義方，早為人君，但知樂，不知苦； ... 閫閾之外，受教於沛王。無怠乃心，以慰予靈。」) Sanguozhi vol. 20.
- (其年薨。詔沛王林留訖葬，使大鴻臚持節典護喪事，宗正弔祭，贈賵甚厚。凡所著文章二萬餘言，才不及陳思王而好與之侔。) Sanguozhi vol. 20.
- (子孚嗣。景初、正元、景元中，累增邑，并前三千四百戶。) Sanguozhi vol. 20.