When Yuan Shao, having defeated Gongsun Zan at Yijing, sent his eldest son Yuan Tan out to govern Qing Province, Ju Shou remonstrated that it would surely be the beginning of disaster. Yuan Shao did not listen, saying he meant to have each of his sons hold one province. In Qing Province Yuan Tan summoned Wang Xiu and made him Attendant Officer of the Headquarters Office, and later appointed him Aide-de-camp. When many local strongmen in Changguang Commandery on the coast rebelled, Yuan Tan even granted them official posts. Records, Wei 6 §49Records, Wei 11 §58Records, Wei 12 §45
In the 4th year of Jian'an (199), when Yuan Shu was in dire straits, Yuan Tan sent men from Qing Province to receive him, but Yuan Shu died of illness on his way north. In the 5th year of Jian'an (200), when Liu Bei, defeated by Cao Cao, fled to Qing Province, Yuan Tan, Inspector of Qing Province, whom Liu Bei had earlier recommended as Flourishing Talent, went out to meet him with infantry and cavalry, accompanied him as far as Pingyuan and reported to Yuan Shao. Records, Wei 1 §56Records, Wei 6 §80Records, Shu 2 §17
At Guandu, when Cao Cao attacked Chunyu Qiong, Yuan Shao said to his eldest son Yuan Tan, 'If I take their camp while they are attacking Chunyu Qiong, they will have nowhere to return to,' and sent Zhang He and Gao Lan. But on hearing that Chunyu Qiong had been defeated, Zhang He and the others surrendered, and Yuan Shao and Yuan Tan abandoned their army and fled across the Yellow River with only a few horsemen. Records, Wei 1 §70Records, Wei 6 §54
Yuan Shao loved his youngest son Yuan Shang, who was handsome, and wanted to make him his successor but did not make it known. Shen Pei and Feng Ji sided with Yuan Shang, and Xin Ping and Guo Tu with Yuan Tan, and the majority wanted to set up Yuan Tan as the eldest. But Shen Pei and the others, fearing that if Yuan Tan were set up Xin Ping and the others would harm them, invoked Yuan Shao's long-held wishes and put Yuan Shang on the throne. When Yuan Shao died in the 5th month of the 7th year of Jian'an (202), Yuan Tan arrived but could not succeed, so he styled himself General of Chariots and Cavalry and garrisoned Liyang, and with this a rift opened between the brothers. Records, Wei 6 §60Records, Wei 1 §76
In the 9th month of that year, when Cao Cao came north to attack, Yuan Shang gave Yuan Tan at Liyang only a few troops and sent Feng Ji along with them. When Yuan Tan asked for more troops and Shen Pei and the others would not give them, he killed Feng Ji in anger. Fearing that Yuan Tan would take over his forces, Yuan Shang came himself with troops and they fought together, but the brothers were defeated again and again, held fast, and in the 3rd month of the 8th year of Jian'an (203) were heavily defeated and fled by night. Records, Wei 1 §76–77Records, Wei 6 §61–62
When Cao Cao reached Xiping on his way to attack Liu Biao, Yuan Tan and Yuan Shang fought each other over Ji Province, and Yuan Tan was defeated and fled to Pingyuan. When his Aide-de-camp Wang Xiu came to his rescue leading officials and commoners, Yuan Tan rejoiced, saying, 'The one who has kept my army whole is Aide-de-camp Wang.' When Liu Xun rose at Tayin and many cities responded, he sighed, 'The whole province turns its back on me; is it not because I lack virtue?' Wang Xiu remonstrated that brothers are the left and right hands, and urged him to behead a few flattering ministers and make peace with Yuan Shang, but Yuan Tan was displeased and did not listen. Records, Wei 1 §80Records, Wei 6 §62Records, Wei 11 §58–61
When Yuan Shang pressed his attack on Pingyuan, Yuan Tan sent Xin Pi to Cao Cao to surrender and ask for help. Xin Pi said that Yuan Shang, seeing Xiansi (Yuan Tan) in difficulty yet unable to take him, had exhausted his strength, and that now was the time to attack Ye; Xun You too urged that with the brothers at enmity this was a moment not to be missed. Cao Cao agreed to make peace with Yuan Tan, and in the 10th month, arriving at Liyang, arranged a marriage alliance with Yuan Tan for his son Cao Zheng. When Yuan Shang's generals Lü Kuang and Lü Xiang surrendered to Cao Cao, Yuan Tan secretly had generals' seals carved and gave them to them. Cao Cao knew of Yuan Tan's deceit but reassured him with the marriage and went back. Records, Wei 1 §80Records, Wei 25 §2–7Records, Wei 10 §61–62Records, Wei 6 §62–63
In the 9th year of Jian'an (204), while Yuan Shang was again attacking Yuan Tan at Pingyuan, Cao Cao attacked Ye. While Ye was under siege, Yuan Tan overran Ganling, Anping, Bohai and Hejian, attacked Yuan Shang at Zhongshan, drove him to Gu'an, and took over all his followers. Cao Cao sent a letter reproaching him for breaking their agreement, ended the marriage alliance, sent his daughter back and advanced. Yuan Tan, afraid, abandoned Pingyuan, took Nanpi as well and garrisoned Longcou, and in the 12th month, when Cao Cao drew up his army before the city gate, he fled by night to Nanpi and encamped overlooking the Qing River. Records, Wei 1 §81 · 87Records, Wei 6 §63 · 67
In the 1st month of the 10th year of Jian'an (205) Cao Cao surrounded Nanpi. Yuan Tan came out to fight and many of Cao Cao's soldiers were killed, so Cao Cao wanted to slacken the attack, but Cao Chun said that to withdraw after coming so far would mean losing his authority, so they attacked fiercely and Yuan Tan was defeated. A cavalryman under Cao Chun cut off Yuan Tan's head, Guo Tu and the others were also beheaded, his wife and children were killed as well, and Ji Province was pacified. Records, Wei 9 §45–46Records, Wei 6 §67Records, Wei 1 §88
Wang Xiu, who was transporting provisions, hurried toward Yuan Tan on hearing he was in danger, but at Gaomi he heard of his death and wept aloud, saying, 'Without my lord, where shall I return?' When Wang Xiu went to Cao Cao and asked to be allowed to collect Yuan Tan's body and bury it, Cao Cao commended his loyalty and granted the request. Records, Wei 11 §61–62
Chen Shou did not assess Yuan Tan separately. The assessment to the biographies of Dong Zhuo, the two Yuans and Liu Biao says that Yuan Shao was magnanimous outwardly but jealous within, and that he set aside his rightful heir and raised a younger son, abandoning proper ritual and exalting favoritism, so that the overthrow of his successors and the toppling of his state were not due to misfortune. Records, Wei 6 §96