Conquest of the Western Turks

Campaign

Ishbara Qaghan (Ashina Helu), a member of the Ashina royal family, was previously a general under Emperor Taizong commanding Tang forces in Gansu. He led a revolt against the Tang and migrated westward, declaring himself Shabulou Qaghan and ruler of the Western Turkic Khaganate. Helu's rise to power unified the divided Turkic tribes under a single leader.

After he established himself as qaghan, Ashina Helu led repeated raids on Tang settlements to the east. He also attacked the Tarim Basin, bringing the territory under Turkic rule for the next six years. Emperor Gaozong, the successor of Taizong, responded by sending Tang forces consisting of a main division led by Su Dingfang, and another led by Ashina Mishe and Ashina Buzhen, Western Turk rivals of Ashina Helu.

Su Dingfang was a commander from south-central Hebei who, earlier in his career as an officer, was responsible for leading the attack against the military camp of Illig Qaghan, qaghan of the Eastern Turks. He also gained military experience as a leader of a regional militia during the civil war fought between the transition from Sui to Tang. Su was a general with military experience in Central Asia, and was familiar with the culture of the steppes. He had been in contact with military leaders from the region. He was one of nine multi-ethnic commanders invited by Emperor Gaozong to a military event in 655. The Turkic general Ashina Zhong, second cousin of Ashina She'er, was another commander in attendance.

Su Dingfang's forces comprised Tang soldiers and 10,000 Uyghur horsemen. The Uyghur troops were provided by Porun, son of the Uyghur leader Tumidu Eltabar and enthroned by Taizong. The Uyghurs were allied with Tang China, who had supported their revolt against the reign of the Xueyantuo, a tribe of Tiele people. Porun joined Su Dingfang as a vice commander of the Uyghur cavalry in the military campaign against the Western Turks. The commanders of the Uyghur cavalry were the Yanran Protector-General and Vice Protector-General, administrators of the Yanran Protectorate near the Tang Xishouxiang military garrison.

Su's army marched through the Central Asian steppes from Ordos, Inner Mongolia to the Altai Mountains region. His troops left Ordos in March and arrived in Kyrgyzstan in November, a journey spanning 3,000 miles across steppes and desert. Su avoided stopping at the resource rich oasis states, and historian Jonathan Karam Skaff speculates that the Chinese troops may have relied on livestock for food instead of a supply train, a tactic used by the steppe nomads. The campaign continued through the winter, when the steppes were covered in snow. Describing the journey's ordeal, Su Dingfang is reported to have said: "The fog shed darkness everywhere. The wind is icy. The barbarians do not believe that we can campaign at this season. Let us hasten to surprise them!"

Commanders in the Tang army were familiar with the political culture of nomadic empires. Nomadic alliances were formed through distributing war plunder and ensuring the security of tribal property, and grew tenuous when rulers failed to deliver their promises. The Chinese understood that disaffected tribes were vulnerable to switching allegiances, and used this to their advantage.

Su Dingfang recruited tribes to side with Tang, and these former tribal vassals of the Western Turks contributed additional soldiers. The tribe Chumukun offered their support after they were defeated by Su, and the tribe Nishu aided Su after their children and wives, originally captured by Helu, were returned along with gifts offered by the Tang.

The battle was fought along the Irtysh River near the Altai Mountains. Helu's forces, consisting of 100,000 cavalry, were ambushed by Su as Helu chased decoy Tang troops that Su had deployed. Helu was defeated during Su's surprise attack, and lost most of his soldiers. Turkic tribes loyal to Helu surrendered, and Helu escaped to Tashkent in modern Uzbekistan. The retreating Helu was captured the next day after residents of Tashkent handed the qaghan over to the Tang. On the way back to the Tang capital, Helu is reported to have written:

I am a defeated and ruined war captive, that's it! The former emperor [Taizong] treated me generously, but I betrayed him. In my present defeat, Heaven has vented its fury at me. In the past I have heard that Han law stipulates that executions of men be carried out in the city marketplace. When we arrive in the capital, I request to Zhaling [the tomb of the previous Tang emperor Taizong] to atone for my crimes to the former emperor. This is my sincere desire.

Gaozong received Helu's plea and agreed to his request, despite a Tang law ordering the execution of captured rebel generals and kings. In accordance with Confucian rituals, he was sent to Taizong's tomb where Gaozong spared his life, and then to the capital's Ancestral Temple where the captive was presented again, mirroring ancient rituals celebrating victorious armies. Helu felt disgraced by Taizong and committed suicide a year later while still in captivity. He was buried in a mound decorated with a stele outside the emperor's park. The tomb served as a military trophy, visible to the emperor's visitors entering the park, symbolizing the loyalty of the qaghan to the emperor and the Tang military victories against the Western Turks.

Historical significance

Aftermath

The conquest strengthened Tang rule over modern Xinjiang, administered by the Anxi Protectorate, and led to Tang suzerainty over the regions previously under the control of the Western Turks. The fall of the Khaganate brought the Altai Mountain region under Tang control and the residing Three Qarluq tribes were governed in newly established prefectures led by tribal chiefs, now commander-in-chiefs under the Tang. Another prefecture, the Jinman Bridle Prefecture, was created for the Chuyue tribes living in the southern Dzungar basin. The Amu Darya valley, the Tarim Basin, and the area beyond the Pamir Mountains, all former suzerains of the Western Turks, were placed under Tang control.

Su continued his career as military general, and later commanded Tang forces in a war against Baekje in 660. The Tang dynasty achieved its maximum extent following its conquest of the Khaganate. The inhabitants of the new territory did not become sinicized like many of the other kingdoms and tribes conquered by the Tang. Tang military activity in Central Asia brought in a wave of Turkic migrants serving in the Tang military as soldiers and generals, leading to the spread of Turkic language and culture. At the same time, the prevalence of Indo-European languages in the Western Regions was on the decline. Central Asia also absorbed cultural influences from Tang China. Central Asian art incorporated Tang stylistic features, like the sancai three color glaze used in pottery. Chinese coins remained in circulation in Xinjiang after the decline of the Tang. Cultural remnants of Tang architectural influence are still visible in the Buddhist architecture of Dunhuang, on the border between the Western Regions and the Hexi Corridor.

The sheer size of the newly conquered lands made it difficult to govern through the Tang military garrisons. The Tang emperor Gaozong appointed two puppet qaghans to rule over the Western Turks, who were later overthrown in a rebellion that began in 662. The revolt reduced Tang's western extent to Beshbalik, Dzungaria in northern Xinjiang and ended direct Tang control of Central Asia beyond the Pamir Mountains in modern Tajikistan and Afghanistan. The expansion of the Tibetan Empire from the south threatened China's hold on southern Xinjiang. Tibet invaded the Tarim Basin in 670, but Tang forces regained the area in 693 and Kashgar in 728, restoring the Anxi Protectorate and Four Garrisons. The conflict between Tibet and the Tang continued for the remainder of the Tang dynasty.

At its maximum extent, Tang expansion brought China into direct contact with the rising Umayyad Caliphate. China's western borders reached the eastern frontier of the Caliphate. Following the Arab defeat of Sassanid Persia in 651, the Caliphate began its expansion into Central Asia, competing with the Tang's sphere of influence in the region. Chinese and Islamic troops finally clashed at the Battle of Aksu in 717 and the Battle of Talas in 751. Though victorious in 717, the Chinese lost against the Arabs, now under Abbasid rule, and the Arab army captured Chinese papermaking craftsmen. An Arabic record of the conflict claims that the battle led to the introduction of papermaking to the Islamic world.

Puppet qaghans

The Tang emperor Gaozong installed two puppet qaghans, the cousins Ashina Buzhen and Ashina Mishe, and controlled the region by proxy. Buzhen and Mishe were enemies of Helu who had aided Su Dingfang during his campaign against Helu and the Western Turkic Khaganate. Gaozong divided the ten tribes of the area among the two cousins. Buzhen governed half of the tribes located in the west, while Mishe governed the other half located in the east.

The son of Buzhen, Khusrau, and the son of Mishe, Yuanqing, resided in Chang'an, the capital of Tang, while their fathers administered the former khaganate as qaghans. Empress Wu Zetian sent Yuanqing and Kusrau westward in 685 to succeed their fathers as proxy rulers.

Neither of the qaghans were able to successfully exert control. Turkic tribes resisted Yuanqing's rule, defeating the qaghan and forcing Yuanqing to return to Chang'an. Kusrau was able to bring the western tribes temporarily under his rule, but was defeated in 690 during an invasion by the Second Turkic Khaganate, and he too was forced to escape the region with his loyalists. Later attempts to install puppet qaghans failed, and the title was reduced to a symbolic position in the Tang court.