The Crisis of Legitimacy in Three Kingdoms China

The mid-3rd century CE presented an unprecedented constitutional crisis in Chinese history – three simultaneous emperors all claiming the Mandate of Heaven. The Wei dynasty under the Sima clan, the Shu Han regime in the southwest, and the Eastern Wu in the southeast each maintained elaborate ideological frameworks justifying their legitimacy. For Sima Zhao, who had recently orchestrated the regicide of Emperor Cao Mao in 260 CE, this legitimacy crisis became existential.

Historical precedent offered only one path to redemption after such a crime – the achievement of unparalleled military conquest. The annals recorded how earlier dynastic founders like Emperor Gaozu of Han had cemented their rule through decisive victories. For Sima Zhao, the calculus became clear: only by eliminating one of the rival claimants to the throne could he transform from regicide to unifier.

The Strategic Calculus: Why Shu?

Among the three kingdoms, Wu presented formidable challenges – its vast territory, naval power, and defensive geography made conquest prohibitively expensive. Shu, by contrast, appeared vulnerable. The psychological advantage also favored this choice – the Sima family had suppressed three major rebellions in the Huainan region against Wu, while Shu’s persistent military activities under Jiang Wei had been a constant irritation.

Yet history cautioned against overconfidence. Cao Cao had famously chased Liu Bei across China like “a wild hare,” only to suffer defeat at Hanzhong. Subsequent Wei campaigns during Cao Pi and Cao Rui’s reigns failed spectacularly against Zhuge Liang’s brilliant defenses. Even recent history showed Shu’s resilience – defector Jiang Wei had repeatedly launched successful raids from his Tazhong base.

The Political Imperative

Three critical factors drove Sima Zhao’s decision:

First, only by conquering the most difficult target could he demonstrate overwhelming power to silence critics. The psychological impact of defeating Shu – long considered impregnable – would far exceed conquering Wu.

Second, Shu’s ideological challenge struck at the heart of Wei’s legitimacy. While Wu’s imperial claims were easily dismissed, Shu maintained it alone preserved the true Han mandate, branding Wei as usurpers. Eliminating Shu would allow Sima Zhao to position himself as the legitimate successor to Wei’s mandate.

Third, intelligence revealed Shu’s unprecedented strategic vulnerability. Jiang Wei’s controversial “Gather Troops, Consolidate Valleys” policy had dangerously weakened Hanzhong’s defenses, leaving fewer than 20,000 troops to guard this critical frontier.

Jiang Wei’s Fateful Strategic Shift

The military situation resulted from Jiang Wei’s radical 258 CE proposal to abandon the proven “Defend Multiple Outposts” strategy that had protected Shu for decades. This traditional approach, perfected by Zhuge Liang and Wang Ping, used Qinling mountain passes as natural choke points.

Jiang Wei advocated instead allowing invaders into the Hanzhong basin, then cutting off their retreat – a high-risk maneuver requiring numerical parity. With Shu’s total forces barely exceeding 100,000 (only 50,000 available for northern defense), this gamble defied military logic. The strategy ignored five critical vulnerabilities:

1. Wei forces could emulate Zhuge Liang’s tactic of establishing frontier agricultural colonies
2. Hanzhong’s population could be plundered or displaced
3. Siege logistics favored the larger Wei army
4. Wei could destroy Shu’s critical infrastructure
5. Any fortress betrayal would prove catastrophic

Most alarmingly, Jiang Wei stationed his 30,000 mobile troops far northwest in Tazhong, leaving Hanzhong dangerously exposed.

The Fatal Bureaucratic Deadlock

When intelligence revealed Zhong Hui’s preparations in 263 CE, Jiang Wei requested reinforcements for Yang’an Pass and Yinping Bridge – the two critical choke points. Emperor Liu Shan, influenced by eunuch Huang Hao’s dismissals and likely distrustful of Jiang Wei’s motives, refused to allocate scarce defensive resources.

This created a fatal impasse: Jiang Wei refused to redeploy without orders, while Liu Shan wouldn’t reinforce until Jiang Wei returned. The standoff played perfectly into Sima Zhao’s hands.

Sima Zhao’s High-Stakes Gamble

Facing near-universal opposition from his advisors, Sima Zhao recognized the campaign’s make-or-break nature. Failure would permanently undermine Sima family ambitions. His choice of Zhong Hui as commander raised eyebrows – many, including Zhong’s own brother, warned of his ambition.

Yet Zhong Hui stood alone in supporting the invasion. His brilliant credentials – from suppressing the Huainan rebellions to outmaneuvering Jiang Wei – made him indispensable despite the risks. Sima Zhao hedged his bets by appointing Wei Guan as military supervisor with an independent force.

The Campaign Unfolds

In autumn 263 CE, after executing dissenting general Deng Dun as sacrifice, the invasion commenced. The strategic brilliance became immediately apparent:

1. Deng Ai pinned Jiang Wei at Tazhong
2. Zhuge Xu blocked potential reinforcement routes
3. Zhong Hui’s main force exploited Hanzhong’s weakened defenses

By the time Jiang Wei attempted to reinforce Yang’an Pass, the strategic situation had already collapsed. The pass fell, dooming Shu’s defensive system.

The Cultural Legacy and Historical Significance

The conquest’s aftermath proved as dramatic as the campaign itself – Zhong Hui’s attempted rebellion and Deng Ai’s tragic downfall became legendary. Yet the campaign’s true significance lay in its geopolitical impact:

1. It established the template for subsequent reunification campaigns
2. Demonstrated how ideological legitimacy could be militarily enforced
3. Highlighted the critical importance of frontier defense policies
4. Showcased how personality conflicts could undermine national security

Modern military theorists still study the campaign for its lessons in strategic overreach, the psychology of command, and the interplay between frontier defense and central authority. The fall of Shu stands as a timeless case study in how empires fall – not just through external pressure, but through internal miscalculation and institutional decay.

For Sima Zhao, the gamble paid spectacular dividends. Within two years, he would posthumously achieve what his father and brother could not – the establishment of a new imperial dynasty. The Jin unification he set in motion would briefly end China’s century of division, though the peace proved short-lived. The conquest of Shu remains one of history’s most consequential military campaigns, reshaping China’s political landscape for centuries to come.