Li Ling was later assigned a military position on the border front, and once led 800 men over 1,000 miles into Xiongnu territory for a reconnaissance mission.
Although he did not encounter any enemies, Emperor Wu soon promoted him to the role of cavalry commander, assigned him to lead 5,000 elite infantries, and placed him in charge of training local reserve forces in Jiuquan and Zhangye.
In 99 BC, Emperor Wu ordered Li Guangli to lead 30,000 men for an offensive from Jiuquan against the Xiongnu in the Tian Shan region.
Li Ling requested Emperor Wu's permission to lead his own regiment to the east, saying that he led a personal legion of "warriors from Jingchu and extraordinary swordsmen", who were capable of "strangling tigers and sharpshooting".
With a large advantage in numbers, the Chanyu attacked Li Ling's forces front-on, only to suffer heavy casualties under the Han troops' crossbow barrage and subsequent pursuit.
Li Ling then discovered that his troops were low in both morale and energy, leading him to search for and kill the many women who were hiding in the wagons and serving as camp followers for his soldiers.
Li Ling's men returned fire from the bottom, depleting 500,000 arrows in one day, and were forced to abandon their wagon transports.
His subordinates suggested the idea of a false surrender, as another Han general Zhao Ponu (趙破奴) previously had done, but Li Ling refused, "Shut up!
Li Ling and his second-in-command Han Yannian (韓延年), each with only a small escort, rode and fought under the pursuit of several thousand Xiongnu cavalry.
[3][2] Emperor Wu initially thought Li Ling was killed in action, and summoned his family to pay tribute.
Emperor Wu was offended by Sima's words of defence, taking them as an attack on his brother-in-law Li Guangli, who had also fought against the Xiongnu without much success.
Although his criminal charges were allowed to be paroled to lesser punishments, Sima Qian was not rich enough to pay for it, so he was forced to accept the commutation to castration and jailed for three years.
[4] Despite his rage, Emperor Wu soon regretted allowing Li Ling to mobilize so hastily and realized it was a mistake to disregard Lu Bode's suggestion.
The Xiongnu responded by having all tribes retreat further north with a scorched earth strategy to challenge the Han army's operational limit.
Ren took the opportunity to talk to Li privately, telling him that all his sins could be forgiven, that he needed not worry about wealth after returning and his old friends missed him.
[12] Some archaeologists have tentatively identified a unique Han-dynasty architecture palace discovered in Russia's Khakassia (southern Siberia) as the residence of Li Ling in the land of the Xiongnu.
When the site was excavated by Soviet archaeologists during 1941–45, they realized that they had discovered a building absolutely unique for the area: a large (1500 square meters) Chinese-style, likely Han dynasty era palace.
While the name of the high-ranking personage who lived there is not known, Russian archaeologist L.A. Evtyukhova surmised, based on circumstantial evidence, that the palace may have been the residence of Li Ling (see ru:Ташебинский дворец).
More recently, for example, it was claimed by A.A. Kovalyov as the residence of Lu Fang (盧芳), a China throne pretender from the Guangwu era.