Deng Ai, a man of Wei during the Three Kingdoms period, lost his father as a child. As an adult, he became a minor officer but was assigned to guard rice fields due to a stutter. Whenever he encountered mountains or marshes, Deng Ai would measure the terrain and plan troop deployments, earning ridicule from others. Later, as an inspector, he traveled to the capital to deliver reports and met Grand Commandant Sima Yi. Sima Yi recognized his talent, promoted him to his own staff, and later elevated him to a senior official position.
Deng Ai, a brilliant strategist and fearless commander, had repeatedly defeated Shu's famed general Jiang Wei, earning promotion to General of the Western Expedition. During the reign of Emperor Yuan of Wei, the court ordered a full-scale campaign against Shu. Jiang Wei retreated to defend Jian'ge Pass, where General Zhong Hui's assault failed. Deng Ai then submitted a bold proposal: "The enemy is battered—we must strike while the iron is hot. If we take the hidden path through Yinping, pass through Deyang Pavilion, and strike Fuxian, 400 li west of Jian'ge and just over 300 li from Chengdu, we will pierce Shu's heartland. The defenders at Jian'ge will have to rush back to save Fucheng, allowing Zhong Hui to advance swiftly. If they don't, the Fucheng garrison will be outnumbered. As the Art of War says, 'Attack where unprepared, appear where unexpected.' Their interior is empty and unguarded—our advance will bring certain victory." Emperor Yuan approved the plan.
Deng Ai then led his army along the narrow path from Yinping, traversing over seven hundred li of rugged, uninhabited mountain terrain. They carved roads through cliffs and built bridges across rivers, facing extreme dangers with deep valleys and steep peaks. Running low on supplies, the entire force was on the brink of disaster. Deng Ai led by example, wrapping himself in a felt blanket and rolling down a precipice; his soldiers followed, clinging to trees and scaling cliffs in a single-file line. Suddenly, Deng Ai's troops appeared at Jiangyou, catching the Shu defenders completely off guard, and the garrison commander Ma Miao surrendered. The Shu general Zhuge Zhan, tasked with protecting the realm, rushed from Fu County back to Mianzhu and formed battle lines to await Deng Ai. Deng Ai ordered his son Deng Zhong, the Marquis of Huitangting, to attack from the right, and Sima Shizuan from the left. Both assaults failed, and the two commanders retreated, reporting, "The enemy is too strong; we cannot break through." Enraged, Deng Ai roared, "Our army's survival hangs on this single battle—how dare you say it cannot be taken!" He harshly rebuked them and threatened execution. Deng Zhong and Sima Shizuan immediately rallied their troops for a second assault, crushing the Shu forces and killing Zhuge Zhan. The Wei army pressed on victoriously to Luo City, where the Shu emperor Liu Shan sent envoys bearing the imperial seal and a personal letter, surrendering to Deng Ai.
After accepting the surrender of the Shu emperor, the Wei general Deng Ai marched into Chengdu. A seasoned warrior who had repeatedly defeated the famed Shu general Jiang Wei, Deng Ai had now finally conquered Shu, earning immense military glory for the Wei kingdom.
Later, the idiom "No Man's Land" came to describe an uninhabited wilderness.
Source: *Records of the Three Kingdoms*, "Book of Wei: Biography of Deng Ai"
Meaning of the Idiom: Later, the Chinese idiom "无人之境" came to describe an uninhabited wilderness.