In the early Eastern Han Dynasty, Emperor Guangwu Liu Xiu had established his regime, but the realm was far from unified. Besides Guangwu, there were Emperor Liu Yong in the east, Emperor Gongsun Shu in Shu, King Peng Chong of Yan, King Zhang Bu of Qi, Grand General Dou Rong of the Five Commanderies, and Grand General Wei Xiao of the Western Provinces—some commanding heavy troops and occupying entire provinces, vying for the empire, while others outwardly pledged allegiance but secretly hoarded their strength, waiting for the right moment to strike.
Emperor Guangwu of the Han Dynasty, ambitious to unify the realm, gathered talented advisors and won the people's support, systematically eliminating rival warlords like Liu Yong, Li Xian, Lu Fang, Peng Chong, Zhang Bu, and Dong Xian one by one.
Then the Grand General of the Five Commanderies, Dou Rong, after carefully assessing the situation, also submitted to Emperor Guangwu. This left only the Grand General of Xizhou, Wei Xiao, and Gongsun Shu, who held the Shu region, as the remaining holdouts.
Soon, Emperor Guangwu sent his envoy Lai She to meet Wei Xiao, urging him to submit. Seeing Guangwu's overwhelming military strength, Wei Xiao reluctantly agreed outwardly, and even sent his eldest son, Wei Xun, to Luoyang to serve as an imperial attendant—in truth, a hostage.
In 30 AD, Emperor Guangwu had pacified the Central Plains and, surveying the situation, believed that with Wei Xiao's eldest son serving as an imperial attendant in the capital, Wei Xiao was no longer a threat, while Gongsun Shu remained far away in the southwestern borderlands. Feeling the realm was largely settled, he remarked to his generals, "Wei Xiao and Gongsun Shu have no power left to stop me from unifying the empire—I can put them out of my mind!"
A few years later, Emperor Guangwu launched a campaign against the warlords Wei Xiao and Gongsun Shu, crushing both separatist forces and reunifying the entire realm under his rule.
Later, the idiom "to set aside" came to describe not taking something to heart.
Source: *Book of the Later Han*, "Biography of Wei Xiao"
Meaning of the Idiom: Later, the Chinese idiom "置之度外" came to describe not taking something to heart.