The Tibetan Empire: From Dominance to Decline in East Asia

The Rise and Fall of the Tibetan Empire: An Overview

The Tibetan Empire’s Golden Age and Its Mysterious Decline

During the Tang Dynasty, the Tibetan Empire, emerging from the Tibetan Plateau, became one of the most formidable powers in East Asia. At its peak, the empire’s domain spanned across the entirety of Western China, extending its military reach into Central Asia and India, competing for regional dominance with the Tang Dynasty, the Uyghur Khaganate, and the Abbasid Caliphate. But what led to the sudden downfall of such a powerful empire?

Factors Behind the Empire’s Ascendancy

The rise of the Tibetan Empire is attributed to a combination of factors, encapsulated in the phrase: right timing, geographical advantage, unity among people, and good fortune.

Right Timing: The Sui and Tang periods experienced a warmer climate in East Asia, including the Northeast. For instance, Longquanfu, the capital of the Bohai Kingdom located in modern-day Ningguta, was in a region that later became bitterly cold, indicating warmer conditions during this period. This favourable climate facilitated large-scale farming in Tibet’s river valleys, providing a solid material base for political and military development.
Geographical Advantage: The Tibetan Plateau’s isolated geography allowed the Tibetans to consolidate power and gradually annexe surrounding regions without external interference.
Unity Among People: Leaders like Songtsen Gampo’s grandfather, Namri Songtsen, and subsequent rulers maintained an attitude of humble inquiry and active improvement. Their efforts were pivotal in transitioning from a tribal society to a slave society, laying the foundations for a powerful empire.
Good Fortune: The Tibetan expansion often coincided with turmoil in neighbouring states and the central Chinese dynasty, which inadvertently facilitated their growth. For instance, the Tibetan conquest of the stronger Subi regime during internal strife significantly expanded their territory and resources.

Agricultural Dominance and Its Collapse

Despite its peripheries being dominated by nomadic tribes, the core of the Tibetan Empire was an agrarian civilization. The rise of the empire was marked by the agricultural civilization’s dominance over nomadic cultures, leading to expanded military campaigns. However, once the agricultural economy declined, the empire crumbled from within.

The Unification of the Tibetan Plateau

The Tibetan Empire unified the Tibetan Plateau by assimilating regions like Subi, under the leadership of figures like Songtsen Gampo. They absorbed part of the Subi aristocracy, such as the Ba and Cai clans, into Tibetan nobility, effectively integrating these regions. Notable Tibetan nobles, like the members of the Gar family, played significant roles in this unification.

The rise and fall of the Tibetan Empire is a tale of strategic conquests, effective governance, and the vulnerability of empires to internal and external pressures. This narrative reflects the complexities of historical empire-building and the impermanence of even the mightiest of powers.

The Strategic Expansion of the Tibetan Empire: A Tale of Conquest and Alliance

Subi: The Tibetan Empire’s Springboard for Expansion

For an extended period, the Subi region served as the Tibetan Empire’s strategic rear base, facilitating its outward expansion. The Subi army, a formidable force in the Tibetan military arsenal, played a critical role in the empire’s ambitious conquests.

Beyond the Tibetan Plateau: The Drive for Expansion

With the Tibetan Plateau unified, the Tibetan Empire naturally set its sights on territories beyond. To the northeast lay the Tuyuhun Kingdom, a power of considerable strength. However, before the Tibetans could make their move, Emperor Taizong of Tang had already significantly weakened Tuyuhun.

Opportunistic Conquest of Tuyuhun

Seizing this opportunity in 637 AD, Songtsen Gampo, recognizing the weakened state of Tuyuhun and the Tang Dynasty’s preoccupation with the Western Turks, launched an attack on Tuyuhun, allying with the Kingdom of Zhangzhung. The Tuyuhun king fled to Tang territory for refuge, prompting the Tibetans to continue their pursuit and attack Songzhou, leading to the first military conflict between Tang and Tibet – the Battle of Songzhou. Initially defeated by the Tibetans, the Tang Dynasty later regrouped and decisively defeated the Tibetan forces.

Seeking Peace Through Marriage Alliance

Recognizing the might of the Tang Dynasty, Songtsen Gampo ceased hostilities and sought peace through a marriage alliance. In 640 AD, Emperor Taizong of Tang sent Princess Wencheng to marry Songtsen Gampo, marking the beginning of a period of relative peace, facilitated by the marriage and Tang’s focus on other fronts.

Expansion into Nepal and Northern India

In the following years, the Tibetan Empire expanded its territories, annexing the Kingdom of Zhangzhung in the Ali region, conquering parts of modern-day Nepal and Northern India, and establishing military outposts along the Ganges River. Notably, after conquering Nepal and Northern India, Tibet did not directly govern these regions but received support from them during military campaigns.

The Tibetan Empire: More Than Just a Highland Power

It’s important to recognize that the Tibetan Empire was not merely a highland power confined to the Tibetan Plateau. At its peak, the empire had a core population of over three million, with over six million in its occupied territories, making it a vast empire with nearly ten million people. This illustrates the empire’s significant reach and influence, far beyond the confines of the Tibetan Plateau.

This historical narrative highlights the Tibetan Empire’s strategic expansion and its ability to capitalize on regional dynamics, solidifying its position as a major power in ancient East Asia.

The Tibetan Empire’s Expansion Under Regent Gar Dongzan

The Passing of Songtsen Gampo and the Rise of a New Leader

In 650 AD, the death of the influential Tibetan leader Songtsen Gampo marked a significant turning point for the Tibetan Empire. His grandson, Mangsong Mangtsen, ascended the throne, but due to his young age, the governance of the empire was entrusted to the capable Regent Gar Dongzan.

Gar Dongzan’s Regency: A Period of Strengthening and Expansion

Gar Dongzan., renowned for his exceptional abilities, used this period to further consolidate and expand the Tibetan Empire’s power. This era of the accumulation set the stage for the empire’s subsequent aggressive expansion.

The Opportunistic Conquest of Tuyuhun

In 663 AD, taking advantage of the internal turmoil in Tuyuhun, Gar Dongzan launched a significant invasion. The Tuyuhun king, unable to resist, fled to the Tang Dynasty for safety. Following this, Gar Dongzan effectively administered Tuyuhun, continuing the policy of assimilation after his death, with his eldest son Zanxirwo taking over. It took seven years for Tibet to fully integrate Tuyuhun and use it as a launching pad for warfare against the Tang Dynasty’s Anxi Protectorate.

The Tibetan Empire’s Major Success in the Western Regions

In 670 AD, Ludongzan’s second son, Gar Triding, led an invasion into the Tang-controlled Western Regions, capturing eighteen prefectures including Baidao (modern-day Xinjiang). He also allied with the Western Turkic tribes of the Karakhanids to capture the city of Kucha (modern-day Aksu, Xinjiang). The success of these campaigns forced the Tang army to withdraw from the Anxi Protectorate, leading to the abandonment of the towns of Khotan, Karasahr, Kucha, and Kashgar. This marked the first major Tibetan success in the Western Regions.

Tang Dynasty’s Response to Tibetan Aggression

Hearing of the Tibetan encroachments on Tang interests, Emperor Gaozong of Tang was enraged and considered military action. Seven years earlier, the Tang Dynasty had contemplated intervening when Tibet annexed Tuyuhun but refrained due to other regional commitments. With the Tibetan foothold in the Western Regions and the instigation of rebellion among Tang’s allies, Emperor Gaozong could no longer afford to concede. He appointed Xue Rengui as the commander of the Tang army and launched a formal war against Tibet.

The Battle of Dafeichuan

Xue Rengui’s appointment signalled Emperor Gaozong’s intent to annihilate the Tibetan forces, as “Luosuo,” the region under his command, referred to present-day Lhasa. Upon receiving intelligence of the Tang offensive, Lunqinling mobilized hundreds of thousands of troops. The Tang forces, led by Guo Daifeng, fell into a Tibetan ambush at Dafeichuan, south of Qinghai Lake, suffering a significant defeat.

This period marks a crucial chapter in the history of the Tibetan Empire, showcasing its strategic military expansions and confrontations with one of the mightiest empires of the time, the Tang Dynasty. The Tibetan Empire’s rise under the leadership of Ludongzan and his sons significantly reshaped the geopolitical landscape of ancient East Asia.

The Tibetan Empire’s Ascendancy and Tang Dynasty’s Struggles: A Shift in Power Dynamics

The Battle’s Aftermath: Rise of the Tibetan Empire

The pivotal battle of 675 AD, where the Tibetan forces shattered the Tang Dynasty’s myth of invincibility, marked a turning point in East Asian history. The Tibetan Empire, once a peripheral power, emerged as a formidable Western force, rivalling the Tang Dynasty. This victory not only elevated Tibet’s status but also incited rebellions in several of the Tang Dynasty’s weaker border regions against its rule.

Tang Dynasty’s Strategic Retreat

To quell these uprisings, Emperor Gaozong of the Tang Dynasty was compelled to further consolidate his military defences, focusing on core areas and abandoning peripheral territories. By 675 AD, after resolving internal conflicts, the Tang Dynasty redirected its military efforts to the Western Regions, eventually reclaiming control over the Anxi Protectorate with assistance from the Kingdom of Khotan.

Tibetan and Turkic Alliance Against Tang

In the following year, seeking retribution against the Tang Dynasty, Lunqinling of Tibet aligned with the Western Turks to launch simultaneous offensives in both the Western Regions and along the Hexi Corridor. The Tang forces, led by Prince Li Xian (later Emperor Zhongzong) and Prince Li Lun (later Emperor Ruizong), were inexperienced and avoided engagement, leading to unchecked plundering by the Tibetan army.

Sudden Death of Tibetan Ruler and a Reprieve for Tang

As the Tang defence lines neared collapse, the sudden death of the Tibetan ruler, Mangsong Mangtsen, forced his successors, Zanxirwo and Lunqinling, to return to Tibet, inadvertently sparing the Tang Dynasty from further losses. In response, Emperor Gaozong issued the “Recruitment of Valiant Warriors” decree, gathering skilled and strong warriors to fortify the army.

The Battle of Qinghai: A Mixed Outcome

The ensuing “Battle of Qinghai” saw the Tang army initially making significant headway, but due to strategic errors by the commanding general Li Jingxuan, the Tang forces suffered a massive defeat, losing over half of their troops in retreat. This defeat prompted the Tang Dynasty to switch from an offensive to a defensive stance, while Tibet launched another round of offensives.

The Stalemate and Changing War Tactics

The subsequent period saw both the Tibetan and Tang armies gaining the upper hand in their respective territories, reflecting a home-field advantage in the early stages of the Tang-Tibetan conflict. This pattern of alternating victories and defeats persisted for over a decade, eventually leading up to Empress Wu Zetian’s consolidation of power and purging of opposition within the Tang court.

This period in history showcases the complex military and political dynamics between the Tang Dynasty and the Tibetan Empire, illustrating the ebb and flow of power and influence in ancient East Asian geopolitics.

The Tang Dynasty’s Military Challenges and the Tibetan Empire’s Political Turmoil

The Impact of Empress Wu’s Purge on the Tang Dynasty

By 696 AD, after Empress Wu Zetian’s sweeping purges, the Tang Dynasty found itself with few experienced military leaders remaining. Seizing this opportunity, Lunqinling of Tibet led a significant offensive into the Hexi Corridor. Empress Wu responded by deploying Generals Wang Xiaojie and Lou Shide with an army of over one hundred thousand to confront the Tibetan forces.

The Battle of Sulohan Mountain

This conflict, known as the Battle of Sulohan Mountain, was a critical engagement with significant losses for the Tang army. Lunqinling, leveraging his tactical advantage and executing a successful ambush, inflicted heavy casualties on the Tang forces. Following this victory, the Tibetan army advanced towards Liangzhou, threatening to seize the entire Hexi Corridor.

Empress Wu’s Strategic Maneuver

Facing imminent danger in the Hexi Corridor, Empress Wu, known for her political acumen rather than military prowess, opted for a strategy of discord sowing. Rumours of Lunqinling’s growing power and potential usurpation began to circulate within Tibet.

The Fall of Lunqinling

Upon hearing these rumours, the Tibetan ruler Tridu Songtsen became apprehensive about Lunqinling’s loyalty and recalled him from the frontline. The following year, leveraging anti-Lunqinling sentiment among the Tibetan nobility, Tridu Songtsen executed Lunqinling and his family, eliminating a significant internal threat to his rule. While this move consolidated Tridu Songtsen’s authority, it was a detrimental loss for the Tibetan military, as no other general could match Lunqinling’s military prowess.

A Turning Point in the Tang-Tibetan Conflict

Lunqinling’s death marked a turning point in the Tibetan Empire’s war efforts against the Tang Dynasty. Over the next fifty years, under the reign of Emperor Xuanzong Li Longji, the Tang Dynasty reached its zenith in terms of national strength and prosperity. The Tang military, revitalized and united under effective leadership, began to gain the upper hand against Tibet.

The Tibetan Empire’s Failing Alliances

In an attempt to reverse its declining military fortunes, the Tibetan Empire sought alliances with the Turks and the Abbasid Caliphate, launching joint attacks against the Tang Dynasty. However, these efforts proved largely ineffective in altering the overall trajectory of the conflict.

This period in history highlights the intricate interplay of military strategy, political intrigue, and leadership dynamics that shaped the course of relations between the Tang Dynasty and the Tibetan Empire. The events following the Battle of Sulohan Mountain not only underscore the importance of skilled military leadership but also demonstrate how internal political strife can significantly impact a nation’s external military engagements.

The Tibetan Empire’s Ascendancy and the Tang Dynasty’s Decline in the Mid-8th Century

The Shift in Power Post-753 AD

By 753 AD, the Tibetan Empire, under the pressure of renowned Tang generals like Geshu Han, Gao Xianzhi, and Feng Changqing, began showing signs of defeat. However, the Tang army, after decades of warfare, had not only neutralized the Tibetan threat in the Hexi Corridor and Western Regions but also extended its frontiers west of Qinghai Lake and the Yellow River bend, seizing the initiative in the conflict.

The Internal Turmoil in Tibet

In 755 AD, amidst ongoing efforts to centralize power and reform domestic policies, the Tibetan ruler Tride Tsuktsen was assassinated by his confidants. This internal turmoil in Tibet coincided with a favourable situation for the Tang Dynasty, which, however, erupted into the An Lushan Rebellion, a turning point in Chinese history.

The An Lushan Rebellion and Tang’s Military Response

In 756 AD, to combat the rebellion led by An Lushan, Emperor Xuanzong of Tang withdrew over a hundred thousand elite troops from the Hexi and Longyou regions to Tong Pass. However, these battle-hardened forces suffered a catastrophic defeat in the subsequent Battle of Lingbao. Emperor Xuanzong fled Chang’an, and Crown Prince Li Heng, at Mawei Post, ascended the throne as Emperor Suzong of Tang.

Tang Dynasty’s Alliance with the Uyghurs

During this period, Emperor Suzong sought to suppress the rebellion by allying with the Uyghur Khaganate. In exchange for military assistance, the Tang Dynasty reallocated its remaining elite forces from the Hexi and Longyou regions to the eastern front, leaving the northwest virtually undefended.

The Tibetan Offensive Under Trisong Detsen

In 763 AD, recognizing the Tang Dynasty’s vulnerability in the northwest, Trisong Detsen, one of the most capable rulers in Tibetan history next to Songtsen Gampo, mobilized a large army to attack Longyou and Guanzhong. Despite the significant eastern advance by the Tibetans, Tang Emperor Daizong, preoccupied with quelling Shi Chaoyi’s rebellion and misled by eunuch Cheng Yuanzhen, failed to address the Tibetan threat adequately.

The Fall of Chang’an to Tibetan Forces

The Tibetan army easily captured Binzhou (modern Shaanxi, Binxian) and subsequently took Chang’an, marking a significant shift in the Tang-Tibetan conflict towards a one-sided struggle against Tang. For the next three decades, Tibet gradually annexed the Hexi, Longyou, and Western Regions while raiding Guanzhong annually, leading to heightened security in Chang’an each autumn.

Trisong Detsen’s Legacy

Trisong Detsen, despite his military successes and effective governance, faced criticism for excessively promoting Buddhism over the indigenous Bön religion. The introduction of Buddhism by Songtsen Gampo had initially balanced Bön influence, but Trisong Detsen’s favouritism towards Buddhism disrupted this equilibrium, sowing seeds of discontent among the Bön followers and setting the stage for future divisions within Tibet.

The period from 753 to the late 8th century witnessed significant shifts in the geopolitical landscape between the Tibetan Empire and the Tang Dynasty, highlighting the impact of military confrontations, internal political strife, and religious dynamics on the course of their prolonged conflict.

The Rise and Fall of the Tibetan Empire: External Pressures and Internal Strife

The Changing Fortunes in the Tang-Tibetan Conflict (753 – 810 AD)

By 753 AD, the Tibetan Empire, previously dominant against the Tang Dynasty, began to falter under the pressure of notable Tang generals such as Geshu Han, Gao Xianzhi, and Feng Changqing. The Tang Dynasty, leveraging these military successes, pushed their frontiers to the west of Qinghai Lake and the Yellow River, gaining the upper hand. However, in 755 AD, an internal assassination within the Tibetan leadership signalled the beginning of internal chaos.

The An Lushan Rebellion and Its Impact on Tang’s Military Strategy

The An Lushan Rebellion in 756 AD, a pivotal event in Chinese history, forced Emperor Xuanzong to withdraw significant forces from the northwest to confront the rebellion. The Battle of Lingbao saw a disastrous defeat for these Tang forces, leading to Emperor Xuanzong’s flight and the rise of Emperor Suzong.

Tang’s Alliance with External Forces and the Tibetan Response

Facing severe external pressures, the Tang Dynasty adopted a strategy of forming alliances with neighbouring powers like the Uyghur Khaganate, Nanzhao, and the Abbasid Caliphate, to encircle and pressure Tibet. This strategy proved successful as Nanzhao turned against Tibet, and the Uyghurs and Tibetans clashed over the Western Regions.

Tibetan Empire’s Strategic Shift and the Longqing Truce (810 – 821 AD)

By 810 AD, facing sustained military campaigns from multiple fronts, the Tibetan Empire temporarily halted its offensives against the Tang Dynasty, focusing on combating the Uyghurs and the Abbasid forces. In 821 AD, seeking peace, the Tibetan ruler Chide Zuzan sent envoys to Chang’an, leading to the historic “Changqing Alliance.” Following this truce, Tibet turned its military attention to the Uyghurs, driving them out of the Tianshan region and incorporating Western Inner Mongolia into its territory.

The Zenith and Decline of the Tibetan Empire

Although the Tibetan Empire reached its territorial peak during this period, it was merely a brief resurgence. Internal religious conflicts, particularly between Buddhism and the indigenous Bön religion, began to erode the empire’s stability.

The Fatal Religious Divide and the Fall of the Empire

Chide Zuzan’s extreme pro-Buddhist policies, including harsh punishments for disrespecting monks, ignited backlash from anti-Buddhist factions. In 841 AD, Chide Zuzan was assassinated, and his brother Langdarma ascended the throne, initiating a campaign to eradicate Buddhism. This shift led to further unrest, culminating in Langdarma’s assassination by Buddhist followers just a year into his reign.

The Final Collapse and Tang’s Reclamation of Territories (842 AD)

By 842 AD, internal divisions within the Tibetan Empire resulted in the formation of two rival political factions, leading to incessant infighting. Seizing this opportunity, Zhang Yichao led a rebellion in Sha Zhou (Dunhuang), rallying the Han population in Hexi and Longyou. The rebels swiftly captured several regions, eventually bringing these territories back under Tang control after many years.

The history of the Tibetan Empire during this era mirrors the decline seen in many central Chinese dynasties, marked by a blend of military setbacks, shifting alliances, and internal religious conflicts that ultimately led to its downfall and the resurgence of Tang influence in the region.

The Decline and Disintegration of the Tibetan Empire

Reclamation of Hexi and Longyou by the Tang Dynasty

As the Hexi and Longyou regions were reclaimed by the Tang Dynasty, the internal situation in the Tibetan Empire worsened dramatically. Various ethnic groups that had been under Tibetan rule, including the Tibetan peasantry and slaves, initiated widespread uprisings against the aristocratic regime.

The Uprisings and Their Sweeping Impact

These rebellions were fierce and engulfed the entire Tibetan region. The slave rebels even captured Lhasa, desecrating the tombs of past Tibetan rulers, except for Songtsen Gampo’s. The slave uprising significantly impacted the warring Tibetan royal factions, leading to their dispersal and further fragmentation into four distinct royal lines: the Lhasa, Ali (later known as the Guge Kingdom), Yaze, and Yalong Jowo lineages.

Emergence of Independent Entities from Tibetan Rule

Additionally, the Gyurme Namgyal regime in Qingtang (modern Xining) emerged as a separate entity from the fragmented Tibetan Empire. By the Song Dynasty, a significant climate shift (average temperatures during the Song were about three degrees lower than in the Tang period) severely impacted agriculture in the Tibetan valleys, contributing to the permanent decline of the Tibetan Empire.

Five Key Factors Leading to the Fall of the Tibetan Empire

The downfall of the Tibetan Empire can be attributed to five primary factors:

Internal Turmoil: The later stages of the empire were marked by intense internal strife and power struggles.
Unsustainable Expansion: The empire’s overextension in its territories led to administrative and military strain.
Militaristic Approach and Numerous Enemies: Constant warfare and the making of too many adversaries weakened the empire.
Religious Factors: The internal religious conflict, especially between Buddhism and the indigenous Bön religion, created significant internal discord.
Climatic Change: The adverse climatic shifts during the Song Dynasty further exacerbated the empire’s agricultural and economic challenges.

The Tibetan Empire’s history of rise and fall is a complex tapestry of military, political, religious, and environmental factors, each playing a critical role in shaping its eventual disintegration and the shifting power dynamics in the region.

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