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Around 211, Cao Ren participated in Cao Cao's campaigns against a coalition of northwestern warlords led by Ma Chao and Han Sui, which led to the Battle of Tong Pass. Cao Ren held the appointment of acting General Who Stabilises the West (安西將軍) and commanded the defence at Tong Pass (潼關; present-day Tongguan County, Weinan, Shaanxi) before Cao Cao reached the frontline.