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 (west of Tong Pass) 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 (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 (), 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.