Background
The assassination of Fei Yi was no chance accident at a drinking party; it was the explosion of a tension that had been building to a breaking point between two rival lines of policy in Shuhan's middle and late periods. Since the death of Zhuge Liang (234), Shuhan's central government had passed through two distinct phases: the Jiang Wan administration, which proposed a new northern-campaign route sending naval forces down the Hanshui toward Xiangyang, and the Fei Yi administration, which reversed Jiang Wan's expansionist line in favor of a policy of consolidating the border and resting the people — foregoing large-scale offensives. The most concrete expression of this restraint was Fei Yi's strict ceiling on the troops he would allocate to Jiang Wei's northern campaigns: no more than ten thousand men per expedition. This cautious line was remarkably successful from the standpoint of restoring national strength, but Jiang Wei — a general personally formed by Zhuge Liang and committed to the northern-campaign cause — was chronically dissatisfied. In the first month of Yanxi 16, Fei Yi was presiding over the New Year's banquet at Fucheng — Shuhan's forward base in the north — when he accepted a toast from the surrendered general Guo Xun. Guo Xun drew a blade and stabbed him; Fei Yi died within days.
Key Figures
Fei Yi, courtesy name Wenwei, was a native of Miancheng in Jiangxia. In his youth he was ranked alongside Dong Yun as one of the finest talents of the age. During the Zhugeliangbeifa campaigns he served as counsellor and chief-of-staff to the Chancellor, and displayed exceptional skill in diplomatic missions to Wu and in managing tensions between generals — one of the "loyal and upright ministers willing to die for their duty" whom Zhuge Liang commended in his Memorial on Sending Forth the Army. Guo Xun (also written Guo Xiu, courtesy name Xiaoxian), a man of Xiping in Liangzhou, had been captured when Jiang Wei campaigned into Liangzhou and subsequently surrendered. His reputation as a man of standing earned him appointment as General of the Left — an unusually high honor for a defector in Shuhan's system. On the night in question, Fei Yi was relaxed with drink and off his guard; Guo Xun approached under the pretext of offering a congratulatory toast and struck. Those nearby killed Guo Xun on the spot. Whether there was a mastermind behind him has been debated ever since: the Wei emperor Cao Fang posthumously enfeoffed Guo Xun as Marquis of Changle, with the posthumous title "Martial" — an explicit act of honor that some historians read as evidence that "Wei had arranged this all along." Others point to Jiang Wei as a suspect, since he had the most to gain; but Jiang Wei's personal relationship with Fei Yi was not hostile, there is no direct evidence, and most serious historians reject this hypothesis.
Core Issues
The assassination of Fei Yi turns on three core questions. The first is Shuhan's limits in handling surrendered enemy commanders. Before the assassination, Yuexi Prefect Zhang Yi had written to warn Fei Yi — citing the cases of Cen Peng and Lai Xi, both killed by assassins — urging him not to relax his guard when receiving defectors. Fei Yi's reply maintained his attitude of "dealing with people with sincere openness." This political style of "moving others through sincerity" worked well enough in peacetime to stabilize defectors, but carried a massive security vulnerability so long as Wei and Shuhan remained at war. The second is the sustainability of Shuhan's "consolidate-and-rest" policy. Fei Yi's death directly severed this line: thereafter Shuhan never again had a figure capable of checking the northern-campaign faction from within the center. Jiang Wei pushed campaign after campaign, culminating in the catastrophic defeat at Duangu in Yanxi 19. The third is the strategic geography underlying the affair. The event took place at Fucheng — a political-military node on Shuhan's northern frontier — and moreover at the most public possible occasion, the New Year's banquet. That an assassin could get close enough is itself evidence of systemic laxity in Shuhan's political screening of border personnel.
Political Consequences
Fei Yi's death directly reshaped Shuhan's political structure. The most immediate effect was a power vacuum at the center: Fei Yi had concurrently held the posts of Grand General, Director of the Masters of Writing, and Governor of Yong Province. After his death these powers were dispersed — Chen Zhi dominated civilian affairs, Jiang Wei monopolized military command, and the eunuch Huang Hao rose within the inner palace. From that point forward Shuhan had no single figure capable of integrating civil and military governance; Chen Zhi and Jiang Wei had no major quarrel with each other, but neither could restrain the eunuch, and Jiang Wei's efforts to check Huang Hao were entirely ineffective. The second consequence was a drastic change in the rhythm of northern campaigns. While Fei Yi was alive, Jiang Wei's expeditionary forces never exceeded ten thousand men. In the very year after Fei Yi's death (254), Jiang Wei began launching large-scale operations: north to Didao in Yanxi 17, to Taoxi in Yanxi 18, to Duangu in Yanxi 19 — a rapid escalation from "annual small-scale harassment" to "annual large-scale decisive battles," and the pace at which Shuhan's national strength was consumed doubled accordingly. The third consequence was the collapse of the system for managing surrendered enemy commanders. After the Guo Xun affair, Shuhan's trust in Liangzhou defectors dropped sharply, and Jiang Wei's efforts to build a united front among the Qiang and Di peoples of Liangzhou became significantly harder.
Counterfactual
If Fei Yi had lived another ten years, Shuhan's trajectory in its later period might have been entirely different. With his political weight, he could have continued restricting Jiang Wei's northern campaigns to ten thousand troops, and Shuhan's national strength would not have been exhausted by the end of the Yanxi era. Even without northern-campaign victories, he could at least have prevented the avalanche of "weakened armies, dwindled commanders, greatly reduced population" that the Duanguzhibai brought on. At a deeper level, if Fei Yi had lived into the late Yanxi years, Huang Hao's rise in the palace would have been significantly slowed, and the three-way imbalance among eunuchs, relatives by marriage, and military men could have been deferred. When Deng Ai later slipped through at Yinping, he would not have found a chaotic capital in which Huang Hao had shelved the warning dispatches — he would have found a Chengdu still functioning steadily under a civil-official establishment. From this vantage point, Guo Xun's single stroke effectively determined, through one man's hand, the pace at which Shuhan collapsed.