During the late Eastern Han Dynasty, chaos engulfed the Guanzhong region as warlords Han Sui and Ma Teng clashed with their armies. To restore order, Cao Cao dispatched Zhong Yao, serving as imperial advisor and minister, to oversee the region's forces as commander. Upon arriving in Chang'an, Zhong Yao wrote letters persuading Han Sui and Ma Teng to make peace, and each sent a son to the capital—ostensibly to guard the emperor, but in truth as hostages. In 208 AD, citing Ma Teng's old age, Cao Cao appointed Ma Teng's son Ma Chao as a general to lead his father's troops, while relocating Ma Teng and his two other sons to Ye, leaving only Ma Chao behind. In truth, Cao Cao harbored deep suspicions toward the Guanzhong generals.
Later, Cao Cao ordered Zhong Yao to attack Zhang Lu, who held Hanzhong, and summoned Xiahou Yuan to combine forces with Zhong Yao. At this, the Guanzhong generals—Ma Chao, Han Sui, Yang Qiu, and Cheng Yi—suspected Zhong Yao was planning to strike them, growing uneasy. They decided to unite against Cao Cao, electing Han Sui as their commander. Han Sui's officer Yan Xing urged him not to rebel alongside Ma Chao, but Han Sui replied, "Now the Guanzhong generals agree without even consulting each other—it's as if Heaven itself has decreed this!" Ignoring Yan Xing's advice, Han Sui led his troops east, clashed with Cao's army at Huayin, and suffered a crushing defeat. All of Han Sui's descendants left in the capital were executed.
Later, the idiom "Without Prior Consultation, Acting in Unison" came to describe actions or opinions that align without prior discussion.
Source: *Records of the Three Kingdoms*, "Book of Wei"
Meaning of the Idiom: Later, the Chinese idiom "不谋而同" came to describe actions or opinions that align without prior discussion.