Why Ancient Wars Always Fought Over Guanzhong and Sichuan

The Geography of Empire: Why Guanzhong and Sichuan Determined China's Fate

When you flip through more than two thousand years of Chinese military history, you'll discover a pattern that repeats itself again and again: whenever the realm descended into chaos and warlords vied for supremacy, the force that ultimately unified the empire almost invariably had an inseparable connection to two places—Guanzhong and Sichuan. The Qin launched from Guanzhong to sweep away the six kingdoms. Liu Bang seized the realm by advancing from Hanzhong and subduing the Three Qins before conquering all under heaven. Li Yuan raised his army from Guanzhong to establish the great Tang Dynasty. Meanwhile, Sichuan served as the foundation of Liu Bei's division of the realm into three parts, was the breeding ground for countless separatist regimes, and remained an indispensable strategic rear area in the unification wars of every era. What exactly made these two places so special that successive generations of ambitious warlords could not help but fight over them? The answer lies hidden in geography itself.

Guanzhong: A Natural Fortress Guarded by Four Gates

Guanzhong refers to the Weihe River Plain region in central Shaanxi Province today, centered on Xi'an (ancient Chang'an). The very name "Guanzhong"—literally "within the passes"—reveals everything about its nature. It was tightly protected by four mighty gates: the Hangu Pass (later the Tongguan Pass) in the east, the Sanguan (Great Sanguan Pass) in the west, the Wuguan Pass in the south, and the Xiaoguan Pass in the north. These four strategic fortresses controlled the main passages in and out of Guanzhong, forming a natural strategic stronghold.

From a topographical perspective, Guanzhong had the Loess Plateau to its north, the Qinling Mountains to its south, the Long Mountains as a barrier to the west, and the Yellow River as a natural defense to the east. In essence, Guanzhong was like a gigantic fortress: enemies attacking from any direction had to contend with towering mountains and hazardous passes. Yet the Guanzhong plain itself was "fertile land stretching for thousands of li." The Weihe River and its tributaries irrigated this plain, and with the construction of water conservation projects like the Zhengguo Canal and the Baique Canal, Guanzhong became one of the most prosperous agricultural regions of its time. The Records of the Grand Historian records that the Guanzhong region had "fertile soil and rich land stretching for a thousand li," and "though its territory was only one-third of the realm and its population only one-tenth, yet in wealth it possessed six-tenths of the empire."

This geographical advantage of "being able to attack when advantageous and defend when necessary" made Guanzhong the preferred base of successive dynasties. Controlling Guanzhong meant possessing a strategically advantageous base that combined offense and defense: when conditions favored expansion, one could march eastward through the Hangu Pass to contend for the Central Plains; when circumstances turned unfavorable, one could seal the passes and preserve strength.

The Qin in Guanzhong: From Frontier Tribe to Unifier of All Under Heaven

The best proof of Guanzhong's geographical advantages was provided by the Qin. The Qin's ancestors were originally a small clan who raised horses for the Zhou royal court, enfeoffed in what is today Tianshui in Gansu. In 770 BCE, when Duke Xiang of Qin earned merit by escorting King Ping of Zhou during the royal migration eastward, he was formally enfeoffed as a lord and granted lands west of the Qi Mountains. Subsequently, the Qin gradually expanded eastward, progressively controlling the entire Guanzhong plain.

The true rise of the Qin began during the reign of Duke Xiao (361-338 BCE). Shang Yang's reforms brought about a dramatic transformation of Qin institutions: abolishing the well-field system, opening pathways between fields, incentivizing agriculture and warfare, and standardizing weights and measures—transforming Qin into an efficient war machine. Meanwhile, Guanzhong's geographical advantages provided a solid foundation for this machine. When the Qin advanced eastward through the Hangu Pass, they could directly threaten the Central Plains states like Han and Wei; if the war turned disadvantageous, they could retreat behind the Hangu Pass and, relying on the strategic terrain, resist even the combined forces of the six kingdoms.

Throughout history, the six kingdoms attempted multiple times to attack Qin through coordinated campaigns, yet nearly every time they were defeated before the Hangu Pass. In 318 BCE, a coalition army from Chu, Zhao, Wei, Han, and Yan attacked Qin but was repulsed at the Hangu Pass. In 247 BCE, the Lord of Xinling led another coalition force against Qin, and though they achieved some victories east of the river, they still could not break through the Hangu Pass. The geographical barrier of Guanzhong saved Qin again and again.

Finally, between 230 and 221 BCE, King Ying Zheng of Qin spent ten years systematically eliminating the Han, Zhao, Wei, Chu, Yan, and Qi kingdoms, achieving the first great unification in Chinese history. This magnificent undertaking originated from Guanzhong, this "imperial foundation."

Marching Secretly Through Chensang: Liu Bang's Struggle for Guanzhong

If the Qin's unification demonstrated Guanzhong's strategic value, then the Chu-Han contention following the fall of the Qin more vividly illustrated the iron law that "whoever controls Guanzhong controls all under heaven."

After the fall of the Qin in 206 BCE, Xiang Yu divided the realm among the nobles. Deliberately, he enfeoffed Liu Bang in the remote regions of Ba, Shu, and Hanzhong, while he himself assumed the title of Hegemon-King of Western Chu and occupied the prosperous Central Plains. Xiang Yu further divided Guanzhong into three parts, entrusting them to three surrendered Qin generals—Zhang Han, Sima Xin, and Dong Yi—to garrison Guanzhong and bar Liu Bang's path eastward. This is the origin of the "Three Qins."

When Liu Bang went to Hanzhong to assume his position, he heeded Zhang Liang's advice and burned the plank roads, signaling to Xiang Yu that he harbored no ambitions to return eastward. Yet mere months later, Han Xin proposed the legendary strategy of "openly repairing the plank roads while secretly marching through Chensang." Liu Bang sent troops to make great fanfare repairing the plank roads, drawing Zhang Han's attention, while he himself led his main force over a small path through Qinling, launching a surprise assault on Guanzhong. Caught off guard, Zhang Han's Three Qins rapidly collapsed.

After seizing Guanzhong, Liu Bang immediately gained an enormous strategic advantage. Guanzhong became his great rear area and supply base, continuously sending soldiers and provisions to the front lines. Xiao He, left to garrison Guanzhong, "transferred resources to supply the army, ensuring supplies never ceased," providing Liu Bang with the capacity for sustained warfare. Thereafter, although Liu Bang was repeatedly defeated by Xiang Yu in direct confrontations, as long as Guanzhong remained secure, he could quickly recover and counterattack. Eventually, after four years of bitter conflict, Liu Bang thoroughly defeated Xiang Yu at Gaixia and established the great Han Dynasty. One might say that the victory in the Chu-Han contention was determined from the moment Liu Bang seized Guanzhong.

The Heavenly Kingdom: Sichuan's Unique Strategic Value

If Guanzhong is the "imperial foundation," then Sichuan is the "heavenly kingdom." The Sichuan Basin is surrounded by high mountains: the Qinling and Daba Mountains to the north, the Wushan Mountains to the east, the Liangshan and Yunnan-Guizhou Plateau to the south, and the Hengduan Mountains on the eastern edge of the Qinghai-Tibet Plateau to the west. This ring of mountains around the basin created an almost completely isolated geographical unit.

Li Bai wrote in "The Difficulty of the Shu Road": "The Shu road is difficult, more difficult than climbing to the blue sky!" This was no literary exaggeration. To enter Sichuan from the north, one must cross the Qinling and Daba Mountains, where suspended plank roads cling to precipitous cliffs—one man defending could stop ten thousand. From the east, entry requires traversing the treacherous waters of the Three Gorges. These natural barriers made Sichuan one of the hardest regions to conquer in ancient times.

Yet within the Sichuan Basin lay abundant prosperity. The Chengdu Plain possessed fertile soil and a warm, humid climate. Combined with the irrigation provided by the Dujiangyan water conservation project (built by Li Bing and his son in 256 BCE), this region became one of the most important grain-producing areas in the nation. The Huayang Guozhi states that in Shu "water and drought obey human will, there is no knowledge of famine, there are no years of dearth, and the realm calls it the heavenly kingdom." Beyond agriculture, Sichuan produced salt, iron, tea, and Shu brocade—important commodities—and its capacity for economic self-sufficiency was exceptionally strong.

This was Sichuan's unique value: it functioned like a natural safe, capable of launching expeditions to contend for the realm when circumstances favored, yet able to seal itself off and peacefully develop its economy and accumulate strength when conditions turned difficult. No matter how chaotically the outside world descended into warfare, as long as a few strategic passes remained secure, Sichuan's interior could enjoy tranquility.

Liu Bei Controls Yizhou: The Foundation of Three Kingdoms Division

The most typical case of Sichuan's strategic value was Liu Bei's establishment of the Shu Han regime. Zhuge Liang explicitly stated in his "Plan for the Longzhong Seclusion": "Yizhou is strategically situated with difficult terrain, possesses fertile land stretching for a thousand li, and is the soil of the heavenly kingdom—the High Ancestor relied upon it to establish imperial rule." This statement was remarkably direct: just as Liu Bang rose to power through Ba, Shu, and Guanzhong in the past, so too should Liu Bei follow this path.

In the nineteenth year of Jian'an (214 CE), after three years of arduous warfare, Liu Bei conquered Yizhou and established the Shu Han regime with Chengdu as its capital. Subsequently, under Zhuge Liang's governance, Shu developed its brocade economy, improved irrigation systems, and achieved great stability. Though Shu Han was the weakest of the three kingdoms with a population of merely one million, by relying on Sichuan's treacherous terrain and prosperity, it persisted for over forty years (221-263 CE) while squeezed between the two powerful rivals of Wei and Wu.

The process of Shu Han's fall further proves Sichuan's defensive value from a negative perspective. In 263 CE, Wei mobilized three armies to attack Shu. The main force under Zhong Hui, numbering over one hundred thousand, was held firmly in check by Shu general Jiang Wei at Jiangedian (south of present-day Guangyuan in Sichuan), unable to advance an inch. Had Deng Ai not risked a daring secret crossing of the Yinping shortcut, scaling the dizzyingly high Mo Tian Ridge to insert directly into the Chengdu Plain, Shu Han might have endured much longer. The reason Deng Ai's secret crossing of Yinping is regarded as a miracle in military history is precisely that this route was so treacherous—Deng Ai himself had to "wrap himself in felt and roll downward." This case amply demonstrates that under normal circumstances, Sichuan's natural barriers were virtually impassable.

Successive Separatist Regimes: Why Sichuan Could Always Form Its Own Kingdom

Surveying Chinese history, Sichuan was one of the regions where separatist regimes appeared with the highest frequency. Beyond Shu Han, there was Gongsun Shu's Chengjia (25-36 CE), Li Te and Li Xiong's Chenghan (304-347 CE), Wang Jian's Former Shu (907-925 CE), Meng Zhixiang's Later Shu (934-965 CE), Ming Yuzhen's Great Xia (1363-1371 CE), and Zhang献忠's Great Xi regime during the late Ming (1643-1646 CE).

These regimes shared a common characteristic: they were almost all established during times of chaos in the Central Plains and contention among warlords. By leveraging Sichuan's natural barriers and abundant resources, they rapidly stabilized their positions and ruled as separatist powers. The case of Former Shu is instructive: Wang Jian was initially a warlord of the late Tang, and by taking advantage of the chaos surrounding the Tang's fall and the turmoil of the Five Dynasties period, he occupied Sichuan and declared himself emperor. Former Shu under his rule experienced economic prosperity and cultural flourishing, becoming one of the most prosperous regimes of its time.

Yet these separatist regimes also shared a common fate: they were ultimately conquered and eliminated by unified dynasties. The reason was straightforward: though Sichuan was easy to defend and hard to attack, it was merely a basin with limited population and resources, unable to sustain prolonged resistance against a unified empire controlling the Central Plains. Once the Central Plains achieved unification and restored its national strength, concentrating forces to conquer Shu became merely a matter of time. The Great Xi regime of Zhang献忠 represented an extreme case: his brutal governance of Sichuan caused the population to plummet catastrophically, and the regime rapidly collapsed under Qing military assault.

Guanzhong Plus Sichuan: The Golden Formula for Unifying All Under Heaven

After analyzing the respective advantages of Guanzhong and Sichuan, a deeper pattern emerges: in ancient China, if a regime could simultaneously control Guanzhong and Sichuan, it possessed the "core foundation" for unifying all under heaven.

The logic of this pattern worked as follows: Sichuan provided a stable rear area and abundant economic resources, while Guanzhong provided an advanced base that could both attack and defend. The two were connected by plank roads such as the Jintniu Road, the Baoxi Road, and the Ziwu Road, forming a complete system of strategic depth. The Qin first controlled Guanzhong, then expanded southwestward to conquer Ba and Shu (eliminating Shu in 316 BCE under Sima Cuo's guidance), thereby acquiring the strength to devour the realm. Liu Bang too first secured Ba and Shu, then seized Guanzhong, ultimately winning the Chu-Han contention.

Conversely, possessing only Sichuan without Guanzhong (as with Shu Han), or only Guanzhong without Sichuan (as with certain short-lived northern regimes), made completing unification exceedingly difficult. Zhuge Liang's five northern expeditions had as their ultimate strategic objective the capture of Guanzhong—"emerging into Qin"—because he profoundly understood that only by connecting Guanzhong and Sichuan could Shu Han achieve reversal of fortune. Regrettably, he died before realizing this goal.

This "Guanzhong plus Sichuan" unification model was not limited to the Qin and Han eras but was verified multiple times in subsequent history. During the late Sui period, Li Yuan rose in rebellion from Taiyuan, rapidly occupied Guanzhong, then pacified Ba and Shu, ultimately unifying all under heaven and establishing the great Tang Dynasty. In the Northern Song unification campaigns, Emperor Taizu Zhao Kuangyin formulated a "south-first, then-north" strategy, one key step of which was first eliminating Later Shu and controlling Sichuan, removing lateral threats before concentrating forces for the northward campaign.

Geography is never the sole determinant of history, yet it does establish certain underlying logic for history's unfolding. Guanzhong and Sichuan—one the "imperial foundation" and the other the "heavenly kingdom"—together constituted the most important strategic puzzle pieces in ancient China's unification wars. Understanding these two regions illuminates more than half the chapter of Chinese military history. The succession of attacks and defenses, advances and retreats, rise and fall enacted upon these lands represent not merely the clever strategizing of military commanders and politicians, but rather the vivid testament to the eternal dialogue between human civilization and natural geography.