Background
In the summer and autumn of the sixth year of Jingyao (263), Sima Zhao of Wei resolved to launch a full-scale invasion of Shuhan. Shuhan's situation at this point was already quite desperate: Jiang Wei's main force was stationed at Dazhong in what amounted to an "evasive agricultural colony" arrangement, separated from Hanzhong and Jiange by a considerable stretch of mountain roads; Hanzhong was defended under the "consolidate troops and stockpile grain" strategy, with Jiang Shu, Fu Qian, and others holding the outlying strongpoints and the primary defense at Yangpingguan; at court Huang Hao trusted the words of shamans and sorcerers and dismissed the frontline warnings, ensuring that the response was delayed until the point of no recovery. Strategically, the entire northern line of Shuhan had already been weakened before the war even began by the dual corrosion of its own "evasive agricultural colony combined with court miscalculation."
Course of Events
Zhong Hui and Deng Ai drove south on more than ten parallel axes. Deng Ai advanced from the Longxi direction directly against Dazhong, his objective being to pin Jiang Wei's main force in place; Zhong Hui stormed Yangpingguan from the Hanzhong direction and captured it swiftly. Only then did Jiang Wei learn that Hanzhong had fallen and Yangpingguan was lost — the original plan of withdrawing from Dazhong northward to meet the enemy had collapsed entirely. He moved south to Qiaotou, where he linked up with the Chengdu relief forces commanded by General of the Left Zhang Yi and General of the Right Liao Hua. This linkup itself revealed the breakdown of Shuhan's defensive command — the relief forces should have reached Hanzhong long before but had been held back by Huang Hao's obstructions and only moved when events had nearly overtaken them.
Decision and Outcome
At the rendezvous at Qiaotou, Jiang Wei initially considered splitting his forces to engage Zhong Hui and Deng Ai simultaneously on more than ten converging axes. Liao Hua's proposal was pivotal: "We are now surrounded on four sides with supply lines cut. It is better to fall back and hold Jiange, then plan from that position" — he pointed out that in the narrow, road-choked terrain of the Baishuidi region no large-scale engagement was possible; rather than being chopped to pieces in unfavorable terrain, the remaining forces should be concentrated at Jiange, "the pass a single man can hold against ten thousand," to maintain the last barrier protecting Chengdu. Jiang Wei hesitated briefly, but the arrival of reports that Deng Ai and Zhong Hui were bearing down on more than ten axes simultaneously left him no choice but to accept Liao Hua's recommendation. This was a rational but pessimistic decision — it surrendered all strategic initiative to the natural obstacle, placing the entire outcome of the campaign squarely on whether Jiange could hold and whether the enemy could find a way around it.
Historical Impact
The choice of Jiange was the last supporting pillar of Shuhan's dynastic fate, and also its greatest vulnerability. From a purely defensive standpoint, Jiang Wei held Zhong Hui's main force at bay at Jiange — Zhong Hui, "with provisions running out and wishing to withdraw," saw Jiange's defensive line succeed on its own terms, and that success is on record. But Deng Ai keenly identified the weakness in this configuration: with Jiange's front firmly held, a flanking march through Yinping — crossing seven hundred li of uninhabited mountain terrain and striking directly at Fucheng and Chengdu — became a viable alternative. Put differently, the decision to fall back to Jiange had no better tactical substitute, but it staked the entire game on the single assumption that "the enemy would also come through the front." The moment Deng Ai crossed through Yinping, the entire defensive value of Jiange was wiped away in a stroke. From a broader perspective, "falling back to hold Jiange" was not only a tactical retreat but also the definitive marker of the end of Shuhan's outward offensive strategy — from this point onward, Shuhan had no possibility of any northward advance whatsoever; the only remaining question was "how long could Chengdu's gateway hold." Some ten-odd days later, Deng Ai's forces reached Chengdu; Liu Chan surrendered. Jiang Wei was still holding out with his troops at Jiange to the last; ultimately he was forced to surrender to Zhong Hui, then attempted to restore the kingdom from within Wei's own ranks — a scheme that failed and cost him his life.