Wubei Zhi (Vol. 12)

Incredible.

"...[these natural] defenses are also sufficient to pacify the borders. If the common people are left undisturbed for several years, the Central Kingdom Referring to the State of Wei, which occupied the traditional Chinese heartland. will grow stronger by the day, while the states of Wu and Shu will surely exhaust themselves." With that, he ceased [his proposal].

Meng Da of Wei had originally been a favorite of Emperor Wen Cao Pi, the son of Cao Cao and first Emperor of the Wei Dynasty.. By this time, however, he felt personally uneasy and frequently exchanged correspondence with Zhuge Liang, plotting to defect back to the state of Shu. Shen Yi, the Governor of Weixing, secretly reported this to the court. Da was gripped by fear and prepared to revolt. At that time, Sima Yi A legendary military strategist of Wei, known as Zhuge Liang’s greatest rival. was stationed at Wan. He sent a letter to comfort and reassure Da, while secretly mobilizing his army to launch an expedition.

Initially, Da had written to Zhuge Liang, saying: "The city of Wan is 800 li liA traditional Chinese unit of distance, roughly 400-500 meters. from the capital at Luoyang, and 1,200 li from the state of Wu. Once they hear that I have taken action, they must submit a formal memorial to the Emperor; by the time the messages go back and forth, a month will have passed. By then, my city walls will be reinforced, and my various armies will be fully prepared. My location is deep and treacherous; Lord Sima will certainly not come, and the other generals are not worth worrying about."

[Contrary to these expectations,] Sima Yi traveled at double speed original: "倍道兼行" (bèidào jiānxíng) — a military term for a forced march where troops cover twice the usual daily distance., and in only eight days his troops arrived beneath the city walls. He captured Da.