Background
The succession crisis of Sun Quan's later years — the Ergongzhizheng — drained the vitality of Jiangdong's founding generation of meritocrats: Lu Xun died in grief and indignation, Zhang Zhao's line withered, and Gu Yong and Zhuge Jin passed away in succession. Before his death Sun Quan designated Zhuge Ke as chief regent, with Teng Yin, Lv Ju, Sun Hong, and Sun Jun as subordinate co-regents. But the political structure was no longer the "joint military-civil governance" centered on émigré-from-north literati that had prevailed in Zhou Yu's and Lu Su's era at Chibi; it was a fragile balance that relied heavily on imperial-clan warlords to overawe the bureaucracy. Structurally, Sun Jun was the only imperial-clan general in the regency council, and he held command of the palace guards. Once Zhuge Ke returned in disgrace from the New City campaign and popular resentment was boiling, the power scales would tilt easily toward this young clansman who held the palace garrison. The five years of autocracy by the Sun Jun–Sun Lin brothers was fundamentally a byproduct of the institutional arrangements Sun Quan made in his final years.
Principal Figures
Sun Jun, courtesy name Ziyuan, was the great-great-grandson of Sun Jing (younger brother of Sun Jian) and son of Sun Gong — young, a remote branch of the clan, but commander of the palace guards and thus the ideal executor of a coup. Sun Lin, Sun Jun's cousin, was by temperament more paranoid and brutal; when he seized power after Sun Jun's death he no longer had the legitimizing cover of "ridding the sovereign of a villain" that Sun Jun had worn, and was left with pure terror as his only governing tool. Those purged in succession by Sun Jun and Sun Lin included Teng Yin (nominally Sun Jun's ally who ultimately joined Lv Ju to resist Sun Lin after Sun Jun's death, was defeated and killed), Lv Ju (the Huainan commander, who took his own life after his forces collapsed fighting Sun Lin), and a string of imperial kinsmen including Sun Yi and Sun Shao. The boy-emperor Sun Liang, enthroned at ten, was throughout a puppet in the imperial clan's hands; Sun Xiu was installed as the new sovereign in the final phase of Sun Lin's dominance and ultimately became the key to overthrowing Sun Lin.
Core Issues
The core issues of this period are three. First: the relationship between imperial clansmen and the regular bureaucracy. When Sun Jun used his clan identity to execute Zhuge Ke he intended to establish his authority through "purging the sovereign's flank," but he and Sun Lin then aggressively expanded clan prerogatives and made the executive position hereditary within the family, rapidly sliding Eastern Wu from "ruler-minister co-governance" toward "imperial-clan military junta." Second: the problem of control over the palace guards. Sun Jun could ambush and kill Zhuge Ke inside the throne hall only because he commanded the palace garrison; Sun Lin likewise deposed and enthroned emperors by controlling the central and household troops, exposing the fact that Eastern Wu's guard system had no mechanism to check the imperial clan. Third: the direction of external military operations. During Sun Jun's tenure he once drove north toward Shouchun, hoping to coordinate with the Guanqiu Jian–Wen Qin Huainan rebellion inside Caowei, but the coordination failed and Liu Zan died of illness en route, leaving the expedition fruitless — a reflection of the military disarray under imperial-clan governance.
Political Consequences
The most direct consequence was the "hollowing-out" of Eastern Wu's central bureaucracy: a succession of senior literati-officials, including Teng Yin and Lv Ju, were executed, further emptying a civil-official corps already weakened by the Ergongzhizheng, leaving Wu in a situation of "imperial-clan dominance, literati absence." Next came the total collapse of trust between sovereign and ministers: Sun Liang had witnessed Sun Jun ambush Zhuge Ke before his eyes in the throne hall, and then saw Sun Lin depose him as Prince of Huiji; he never trusted the imperial clan again. That shadow of distrust extended through the reigns of Sun Xiu and Sun Hao, ultimately flowering into Sun Hao's extreme suspicion and slaughter of imperial kinsmen. Third was military decline: the northern thrust toward Shouchun failed; the generals cultivated since Yiling were more than half lost to internal strife; Wu thereafter produced no supreme commander of Zhou Yu's or Lu Xun's caliber until Lu Kang's twilight years partially restored order.
Counterfactual Analysis
Had Sun Quan at his deathbed excluded Sun Jun from the regency council and entrusted governance jointly to three non-clan figures — Zhuge Ke, Teng Yin, and Lv Ju — then even after Zhuge Ke's military defeat he would most likely have been removed from office rather than ambushed and killed overnight. Eastern Wu could in that scenario have avoided five consecutive years of imperial-clan autocracy and infighting, brought a generation of talent like Lu Kang to the fore earlier, and mounted a more effective response to the pressure from the western front after Shuhanmiewang. Conversely, had Sun Jun not died early and Sun Lin not inherited his position, Sun Jun — still retaining his "executer of the villain" public credit at that point — might have gradually stabilized into a figure resembling Sima Shi, a steady executive working within the system. Wu's collapse would have been delayed but its endpoint unchanged. Whichever fork one takes, the combination that Sun Quan bequeathed at the end of his life — "imperial clansmen holding the palace guard + a child as successor" — had already set Wu on a track toward institutional crisis; autocracy was merely the outward symptom.