Xiahou Dun served Cao Cao since he first raised an army, fighting in the Yellow Turban Rebellion in 184 AD. His first major mention, however, came when he joined the alliance against Dong Zhuo in 189 AD, saving his brother from Dong Zhuo's guards in Luoyang when he failed to kill the tyrant. Xiahou Dun later served at the Battle of Hu Lao Gate, which was the first battle of his brother Xiahou Yuan. He distinguished himself in the Battle of Yingyang by saving Cao Cao from Xu Rong, spearing the officer while defending his cousin. This battle solidified his position as Cao Cao's right-hand man, and proved his loyalty to his cousin.
Dun lost his eye in battle while coming to the aid of Liu Bei in 196 AD in the Battle of Puyang in Yan Province. His eye was hit with an arrow fired by Lu Bu's general Cao Xing, covering the retreat of General Gao Shun. To scare his foes (and Xun Yu, his own general, unwittingly), he took the arrow, eye still attached, and ate it. He stopped Xiahou Yuan from impaling Cao Xing with an arrow, instead chasing him down and stabbing him in the face with a spear. Gao Shun inflicted a severe defeat on Xiahou Dun when he retreated, but he had reaped his revenge and infamy.
Xiahou Dun took part in the other campaigns of Cao Cao in the 190s, including the suppression of the Yellow Turbans in Yan Province, the war against Zhang Xiu, and the Battle of Xia Pi in 198 AD. He also fought in the wars against Yuan Shu, Yuan Shao, and Liu Bei, although he was defeated by Guan Yu at Xiangyang, causing the city's fall in 209 AD.
Dun continued to fight for Cao Cao's Forces into his older years in the dark times of Wei during the 210s, suffering many defeats by Shu in Hanzhong in 219 AD. However, he redeemed himself by assisting in the Wei victory at Fan Castle later that year, and was the one who killed the great warrior Guan Yu. His murder of Guan Yu was famous, as it also involved the betrayal of Shu by Wu, who came as support for Wei. Xiahou Dun died a year later, the same year as Cao Cao.