During the Western Han Dynasty, the Xiongnu frequently raided the northern borders. In 100 BC, a new Xiongnu chanyu had just taken power and sent envoys to Chang'an to seek peace. Emperor Wu of Han, treating them with courtesy, dispatched imperial advisor Su Wu as an envoy to the Xiongnu, while also sending cavalry commander Li Ling with 5,000 troops to garrison and train in the Zhangye and Jiuquan regions as a precaution.
Su Wu and Li Ling were close friends, and before Su Wu departed on his mission to the Xiongnu, they encouraged each other, vowing to serve the imperial court with utmost dedication.
After arriving among the Xiongnu, their Chanyu broke his promise and detained Su Wu. When attempts to force his surrender failed, they sent him to herd sheep by the shores of Lake Baikal.
The following year, Emperor Wu ordered General Li Guangli to lead an attack on the Xiongnu and planned to assign Li Ling to handle logistics. However, Li Ling, grandson of the famed general Li Guang, refused to serve under Li Guangli. He proposed to the emperor, "I need only 5,000 infantry to strike directly at the Xiongnu's stronghold." Impressed by his bold spirit, Emperor Wu granted his request.
That autumn, Li Ling led 5,000 infantry northward. After over 40 days of grueling march, they encountered 30,000 Xiongnu cavalry. Surrounded, Li Ling ordered his men to fight to the death, striking the Xiongnu hard. The Chanyu was forced to retreat, and Li Ling pressed the advantage, annihilating over 2,000 more enemies.
Refusing to accept defeat, the Chanyu summoned over 80,000 cavalry and launched a fierce assault on Li Ling's army. Seeing the overwhelming disparity in numbers, Li Ling fought while retreating, killing more than 3,000 Xiongnu soldiers. The Chanyu, suspecting a Han ambush, hesitated to advance. At this critical moment, a minor Han officer named Guan Fang defected to the Xiongnu and revealed, 'Li Ling has only 3,000 men left, and they are completely out of arrows and supplies.'
The Chanyu was overjoyed and immediately ordered a full-scale attack. The Xiongnu cavalry charged fiercely, and Li Ling's troops suffered heavy casualties. At this moment, Li Ling raised his arm and shouted, "Fight bravely, kill the enemy!"
Hearing Li Ling's rallying cry, his soldiers fought desperately against the Xiongnu, but outnumbered and exhausted, two days later Li Ling was captured by the enemy.
When Emperor Wu received the report of defeat, he was furious. Hearing that Li Ling had surrendered to the Xiongnu and was advising them, he ordered Li Ling's family executed—though Li Ling had not yet done so at the time.
Later, the Chanyu married his daughter to Li Ling and appointed him King of Youling. When Su Wu, tending sheep at Lake Baikal, learned of this, he wrote a letter rebuking Li Ling for surrendering to the Xiongnu. Receiving the letter, Li Ling felt both sorrow and shame. In his reply, he recounted his heroic resistance against the Xiongnu and explained his surrender was unavoidable. He also accused Emperor Wu of ingratitude and cruelty for executing his entire family.
Later, people used the idiom "Raise an Arm and Shout" to describe raising one's arm and issuing a call.
Source: *Selections of Refined Literature*, "Li Ling's Reply to Su Wu's Letter"
Meaning of the Idiom: Later, the Chinese idiom "振臂一呼" came to describe raising one's arm and issuing a call.