函谷関
Cao Cao, after resting his forces for several years in light of his defeat at the Battle of Red Cliffs, made a major advance again in 211, this time to ostensibly attack Zhang Lu of Hanzhong. Warlords Han Sui and Ma Chao, who controlled Liang and Yong provinces, suspected that Cao Cao had designs on them and launched attacks in retaliation. A coalition of forces from west of Hangu Pass, led by Ma Chao and Han Sui, was defeated by Cao Cao at the Battle of Tong Pass in 211, and their territories were annexed by Cao over the next few years.