Geng Yan was a man of sharp intellect and strategic brilliance from his youth, skilled in horseback archery and deeply versed in military formations.
In 23 AD, the Xin dynasty established by Wang Mang collapsed, and Emperor Ai of Han, Liu Xin, ascended the throne. As regional generals raised armies and seized local power, replacing governors and magistrates, Geng Yan's father, Geng Kuang, grew uneasy knowing his own post had been appointed by Wang Mang. So the 21-year-old Geng Yan bid his father farewell and set off to present tribute to Emperor Ai, hoping to secure his family's position.
One day, General Geng Yan encountered a man on the road who falsely claimed to be Liu Ziyu, the son of Emperor Cheng of Han, and had raised an army in Handan. The officials Sun Cang and Wei Bao, who were with Geng Yan, urged him, "Liu Ziyu is the emperor's son and the rightful heir to the Han throne. We should submit to him to find a way forward. If we miss this chance, where else can we go?"
Geng Yan's face turned stern as he pressed his hand on his sword hilt and declared, "That scoundrel Liu Ziyu is nothing but a future prisoner. I will go to Chang'an, join the imperial forces from Yuyang and Shanggu, sweep through Taiyuan and Dai commanderies, and return in a matter of weeks to crush those rabble like rotten wood. You fools cannot see the danger—your entire clan will be wiped out before long."
Sun Cang and Wei Bao, ignoring Geng Yan's advice, defected to a man surnamed Wang.
On the road, Geng Yan heard that Liu Xiu was in Luno, so he went to join him, earning Liu Xiu's trust. He repeatedly defeated enemies and won victories, making great contributions to Liu Xiu's conquest of the empire and his ascension to the throne.
Later, the idiom "a disorderly crowd" came to describe a hastily assembled group of useless people.
During the Eastern Han Dynasty, the young general Geng Yan proposed a bold plan to Emperor Guangwu: to pacify the powerful warlords in the north. The emperor, impressed by his ambition, asked, "Can you truly accomplish this?" Geng Yan replied with confidence, "Your Majesty, I will cover a thousand li in a single day, striking like lightning before the enemy can react." True to his word, Geng Yan led his troops with incredible speed, defeating the enemy forces in a series of swift campaigns. When the emperor later praised him, Geng Yan humbly said, "It was Your Majesty's strategy that guided me; I merely followed the path you laid out." This story gave rise to the idiom "A Thousand Li a Day," symbolizing extraordinary speed and decisive action. Source: *Book of the Later Han*, "Biography of Geng Yan".
Meaning of the Idiom: Later, the Chinese idiom "乌合之众" came to describe a hastily assembled group of useless people how a thousand li a day symbolizes extraordinary speed and decisive action.