Wen Dan
Wén Dān, proposed to correspond to Mūladeśa, a toponym attested in the K.187 Inscription, refers to a group of early Tai political entities that existed between the 6th and 9th centuries CE in the interior of mainland Southeast Asia, primarily distributed across the central Mekong Valley in what is now northeast Thailand. It was mentioned in the Chinese annals of the Tang period as a dependency on the trans-Mekong trade route from the ancient city of Chiaochih to India. It sent representatives to China in 717, 750, 753, 771, 779, and 799. Some scholars have identified Wen Dan with Bhavapura, whose location remains debated, and have suggested that it may have been the place from which a unified Chenla emerged. However, this view is disputed. Other scholars place the formation of Chenla in the southern Tonlé Sap Basin rather than in Northeast Thailand or southern Laos, a position consistent with Claude Jacques’s argument that Sambor Prei Kuk itself was Bhavapura.
Initially, Wen Dan was believed to be Vientiane, but according to the location given in the Chinese annals as well as archaeological evidence, it is supposed to be in the Chi River basin, centered in Kantharawichai — which was called the Chinese as Pó Lòu — with Mueang Fa Daet Song Yang as outer center and Champasri as the vassal. It was alleged that these three communities had a close relationship through Dvaravati Buddhism, which was subsequently supplanted by the Angkorian beliefs in the 10th century. Several historical evidences supports the connection between Wen Dan and Si Thep in central Thailand. Its capital's location at Kantharawichai corresponds to the details provided in the Chinese text of Tang Huiyao says Wen Dan was a state located 6 days' travel by land northwest of Dvaravati-influenced Keoi Lau Mì of the Kuy people.
According to the Dvaravati Buddhist boundary stones dated the 8th century, found on Mt. Kulen, Woodward proposes that Wen Dan once controlled the Angkor region before Jayavarman II proclaimed the independence of the Kambujadesa from Java in 802. Jayavarman II probably either defeated Wen Dan and then moved the capital from Indrapura to Yaśodharapura to the north, or formed ally with the communities in Mun and Chi watersheds to against Si Thep to the west.
Wen Dan had two vassals, including Dàomíng to the north in modern Laos, and Cān Bàn in the upper Pasak River Valley in central Thailand. Some academics equate Wen Dan with Bhavapura, centered at Vat Phou in modern southern Laos, which is opposes to the location of Wen Dan provided in the Chinese source.
History
Dvaravati–Chenla period: 580s – 800s
Federated Chenla: 580s – 681
It was proposed by Pierre Dupont that Chenla was originated in the Mun Valley, and was ruled by the Bhavavarman I, who, together with his successor Mahendravarman I, expanded territory southward to the Bassac-Pakse region, which considered the original land of the Khmer people that later known as Sreshthapura. The expansion campaign continued deep south along the Mekong Basin, and they successfully established the new capital at Sambhupura in 618. The reign of their successor, Isanavarman I, was considered the golden period of the kingdom, as he was able to subdue the maritime trade polity of Funan, which previously was their suzerainty, as well as vassalizing several polities to the northwest in the Tonlé Sap Basin, extending the influence to the Menam Valley in modern central Thailand, where the Dvaravati culture dominant. Following the reign of Isanavarman I, Chenla declined and eventually broke apart in the 8th century.The aforementioned presupposition; however, has recently been questioned as Khmer inscriptions that date pre-7th century are found to be concentrated in present-day central to southern Cambodia and the Mekong delta in southern Vietnam. In contrast, northeastern Thailand has no Khmer inscription dated before the 8th century, as well as the adjacent area of southern Laos and northwest Cambodia, previously stated to be the original homeland of Khmer, were instead dominated by Cham inscriptions. Thus, Bhavavarman I and Mahendravarman I probably originated in the southern plain of the Tonlé Sap, to be specific – the Sambor Prei Kuk, and later expanded their influence northward to Bassac-Pakse and the Chi-Mun Valley. However, these expeditions or exploratory ventures appear to have had little lasting political impact, as regional inscriptions for several subsequent centuries make no reference to rulers from the Tonlé Sap Basin following the period associated with Mahendravarman.
The origin of Bhavavarman I remains disputed; he was potentially a prince of Si Thep's king, Prathivindravarman, as cited in the K.978 Ban Wang Pai Inscription. This assumption is corroborated by numerous archaeological findings in the proposed regions of Wen Dan, encompassing Kantharawichai, Mueang Fa Daet Song Yang, and Champasri, showing a substantial connection to Dvaravati's Si Thep in central Thailand.
Independent polity: 681 – 800s
Attributing the secession of Upper Chenla or Wen Dan to weakened authority at Sambhupura, Pierre Dupont proposed that it broke away in 707 and that the resulting polity was named "Bhavapura" in honor of its first prominent ruler, Bhavavarman I. By contrast, George Cœdès identified this polity with "Mūladeśa", a toponym attested in the K.187 inscription, and dated the separation to the end of Jayavarman I’s reign, around 681. Tatsuo Hoshino has suggested that Kantharawichai was likely the principal city of Wen Dan, while other scholars have proposed alternative locations, including Thakhek or Mueang Fa Daet Song Yang. The remaining loosely associated polities of Lower Chenla – Sambhupura, Vyādhapura, and Bālādityapura – are generally understood to have dissolved by the late 8th century.Following the secession, Wen Dan was probably ruled by Bhavavarman I's offspring. It was believed that Sri Jayasimhavarmman, cited in the Monic K.404 Stèle de Phu Khiao Kao found in Chaiyaphum province, dated 7th–8th century, was the first Wen Dan king. The sole historical documentations concerning Wen Dan during this period are the Chinese records from the Tang Dynasty, which provide more insight into Wen Dan's relations with China than its dealings with the lower Chenla. The travel route to China clearly through the Annamite mountain passes to Nghean, and thereafter to Jiaozhou.
Wen Dan first sent tribute to China in 717. Subsequently, in 722, Wen Dan assisted a native Nghean lord – probably a Tai or a Hmong – in the wars against the Chinese governor at Jiaozhou, which they won, conquering Jiaozhou, and the native lord enthroned himself as Hei-ti. This royal connection allowed the Tai–Lao people to start migrating to the Khorat Plateau during this time. The tribute to China was probably sent again in 750. Three years later, Wen Dan's crown prince, together with 26 relatives, visited the Chinese court, and the prince was given the title "Protector Firm and Persevering" for Wen Dan's assistance in helping to guard its southeastern frontier. Following the Tang dynasty's defeat in the trade routes conflicts by King Kolofong of Nanzhao in 753 and 755, Wen Dan's king dispatched his crown prince and generals to support China, but the Chinese armies were routed.
Due to several unsuccessful wars against Nanzhao, to strengthen the southern region, Jiaozhou was placed under a military commandant in 756. Ten years later, in 766, a Tang army of 70,000, led by General Li Mi from Sichuan, invaded Nanzhao. Vietnamese Governor "He Lu Guang" joined Wen Dan in attacking the south Nanzhao, but Kolofeng, the Nanzhao king, captured General Li and won. Wen Dan's army returned home. The following year, the citadel of Lo-than near the modern Hanoi was constructed after the region was raided by Melayu, the viceroy of Wen Dan, with his wife, then came to court to pay 11 trained elephants. In 771, Wen Dan's prince went to China and was titled "Special Highest Local Commander," equal to the King of Nanzhao, and was even higher than the Chinese governors in Vietnam and Guangzhou. Another embassy is said to have been sent in 779, and the last one in 799. A Chinese merchant named Chia Tan paid a visit to the Wen Dan capital in the late 8th century. His itinerary for the journey also cursorily provides the location of Wen Dan, whose capital is potentially in the Chi River Basin in Thailand or near Thakhek in the present-day Laos.
No record mentions Wen Dan after the last tribute sent to China in 799. If Wen Dan was Bhavapura as proposed by some scholars, it was probably under the ancestors of Rajendravarman II, who, through his dynasty, later brought the kingdom under Yaśodharapura during his reign at Angkor from 944 to 968. Hiram W. Woodward proposed that after Kambujadesa' king Jayavarman II moved the capital to the north of the Tonlé Sap in the late 9th century, he probably formed alliances with polities in the Chi–Mun basin, which includes Wen Dan, to counterpoise Si Thep in the Pasak basin to the west.
Japanese scholar Tatsuo Hoshino suggests that, following the end of the Wen Dan or trans-Mekong confederated city-states period around the 800s, the region entered a new period, known as Java, and its successors were standing at the threshold for the new era for Tai-speaking people of Southeast Asia.
Java – Angkorian period: 800s – 1300s
Despite its disappearance from the historical record after the early ninth century, if Wén Dān is to be identified with Bhavapura, it may have continued to exist in a subordinate or dependent capacity until the accession of Rajendravarman II —himself a member of the Bhavapura lineage—to the Angkorian throne in 944. Through his lineage, Bhavapura was brought under Yaśodharapura during his reign, expanding the Angkor territory to Laos and the eastern Menam Valley in central Thailand, as far north as southern China – possibly through an alliance formation with local chiefdoms to defend against Nanzhao in the 8th century – and also won over Champa. Rajendravarman II was followed by his ten-year-old son Jayavarman V, during whose rule royal politics were dominated by aristocratic families, which led some vassals to break away. The kingdom then entered a nine-year civil war, and the throne was won by an usurper Suryavarman I in 1006.Another proposed center of Wen Dan at Kantharawichai, or Gandharath in the local chronicle, was abandoned following the fall of the Dvaravati civilization in the 10th century. Its southern vassal, Champasri, evolved to Yamanadvipa but was later deserted in the 14th century, due to the invasion by King Fa Ngum of Luang Phrabang after he successfully reunited the Laotian Kingdoms, whereas, the outer center at Mueang Fa Daet Song Yang, founded in 621, was maintained until its decline in importance in the 17th century. Wen Dan was probably replaced by a semi-legendary Laotian kingdom of Kuruntha, centered at Saket Nakhon, as local legend claims its territory covered two former Wen Dan polities, Mueang Champasri to the west and Mueang Fa Daet Song Yang to the north.