Background
After Crown Prince Sun Deng died in the fourth year of Chiwu (241), the Sunwu regime entered a vacancy at the heir apparent's position. The following year (242) Sun Quan established his third son, Sun He, as crown prince; within months he also enfeoffed his fourth son, Sun Ba, as Prince of Lu — and in ceremonial treatment, privileges, and staff allocation came close to matching Sun He's rank as crown prince. This effectively sent an open signal to court officials that they could pick sides. Sun Ba thereupon harbored ambitions to usurp the succession, and relations between him and Sun He deteriorated into outright enmity. Over the ensuing eight years (242–250), the "Ergongzhizheng" — the Struggle of the Two Palaces — completely split the Sunwu court: Lu Xun, Gu Tan, Zhu Ju, and Wu Can supported the crown prince; Bu Zhi, Lv Dai, Quan Cong, and Lv Ju attached themselves to the Prince of Lu. The two factions attacked each other relentlessly, while an aged and suspicious Sun Quan vacillated between them — until in the thirteenth year of Chiwu (250) he made an all-or-nothing decision: purging the leading figures of both sides simultaneously and establishing his young infant son, Sun Liang, as heir [c:16886].
Key Figures
Sun Quan was close to seventy at this point, with only two years left to live. His late-life decision-making had visibly deteriorated, bearing little resemblance to the flexible and pragmatic figure he had been in his younger days. Crown Prince Sun He was diligent in government and courteous in manner, with a strong inclination toward civil administration; he was held up as the hope of the Confucian-minister faction led by Lu Xun. Prince of Lu Sun Ba, relying on imperial favor, had cultivated connections among northern-refugee aristocrats and a portion of meritocracy-based old guard families, and his influence had swollen considerably. Sun Liang was only around eight years old at the time, the son of Sun Quan's favored consort Lady Pan, and was pushed onto the succession as a compromise candidate belonging to neither faction. Lu Xun, as Sunwu's supreme military commander and Senior Grand General, repeatedly submitted sealed memorials to Sun Quan urging restraint throughout the Ergongzhizheng, and was ultimately berated by Sun Quan through a series of envoy missions in the eighth year of Chiwu (245), dying of grief and indignation — Lu Xun's death was one of the heaviest costs of this factional struggle.
Core Issue
The political science question of this event is: when a ruler has lost trust in both factions, is "beheading both" a stable solution? Sun Quan's calculation was: deposing Sun He would ensure the crown prince faction could not stage a comeback; having Sun Ba put to death would eliminate the physical foundation of the Prince of Lu's faction; installing a young child as ruler would leave both factions with no one to attach themselves to — on the surface this was "zeroing out power and reshuffling the deck." But this approach overlooked two critical facts. First, the official families who had participated in the factional struggle had already grown deeply and intricately intertwined; executing Sun Ba alone could not eliminate the networks of aristocratic clans behind him. Second, the newly installed Sun Liang was far too young, and would inevitably require a powerful regent — transferring the power vacuum from the imperial family to the regent's hands, and thereby planting the seeds for the successive dictatorships of Zhuge Ke, Sun Jun, and Sun Lin.
Political Consequences
After the events of 250, four cascading reactions struck Wu's political landscape. The first was massive loss of talent: the high officials who were convicted, killed, or exiled in connection with the Ergongzhizheng numbered in the dozens; after Lu Xun's death, Sunwu's supreme military commander was never again matched; Gu Tan, Wu Can, Zhang Xiu, and others also died successively in prison or in exile. The second was the collapse of aristocratic-clan trust: the great Jiangdong clans — Gu, Lu, Zhu, Zhang — had originally been the core pillars of the Sunwu regime; the Ergongzhizheng forced them into the dilemma of either silent self-preservation or picking a faction side. The third was the malformation of the regency system: on his deathbed Sun Quan entrusted governance to Zhuge Ke, Sun Hong, and others — yet Zhuge Ke, having come to power in 252, grew arrogant and overbearing after the victory at Dongxing and was killed in a coup by Sun Jun; Sun Jun then dominated, followed by Sun Lin who deposed the emperor — this entire spiral of chaos stemmed directly from Sun Liang's weakness and lack of a stable political base. The fourth was strategic stagnation: the Ergongzhizheng exhausted Sunwu's political capital in its middle-to-late period, and the alliance with Shu and offensive against Caowei were shelved; from this point Sunwu entered a posture of strategic defense and never again possessed the capacity for proactive military action.
Counterfactual Analysis
Suppose Sun Quan had at the time established a young son of Sun Deng or an elder kinsman as crown prince, without elevating Sun Ba to near-equal ceremonial status with Sun He — the Ergongzhizheng would never have occurred, and Sunwu might have completed its generational transition in a far more stable fashion, leaving Lu Xun to continue serving and the great Jiangdong clans to remain loyal to the new regime. Suppose further that Sun Quan had moved early and decisively in the Ergongzhizheng to protect Sun He and depose Sun Ba — though this would have temporarily alienated the Prince of Lu's faction, it would have preserved an adult heir with genuine governing capacity, avoiding the situation of Sun Liang's infancy and the chaos of regency. Suppose further that Sun Quan had chosen to protect Sun Ba and depose Sun He — the outcome might not have been any better, but at least the succession struggle would not have dragged on for eight years. All three counterfactuals point to the same conclusion: the root of the Ergongzhizheng was Sun Quan's deteriorated judgment in old age, and the "double beheading" of 250 was not a resolution of the problem but a packaging of the problem and a handoff to the next generation. Later historians — Pei Songzhi, Sima Guang — have broadly identified this purge as the watershed event of Sunwu's decline, placing it alongside the Gaopinglingzhibian of Caowei and Shuhan's defeat at Yiling as the three great political catastrophes of the San Guo's later period.