The specific military conflicts which occasioned resettlement of Black Tai communities occurred at the close of the reign of King Boromaja IV (Taksin of Thon Buri) and beginning of the present Chakri dynasty in the early 1780's, extending to the late nineteenth century during the reign of Rama V. In the history of Tai-speaking peoples in Southeast Asia, this is relatively late. The context of Black Tai and Lao Song ethnogeneses is, however, a persistent social, economic, and geopolitical pattern which dates back to the earliest period of Tai expansion into mainland Southeast Asia.

By the tenth century A.D., small groups of .Tai speakers migrating gradually south from the Yangtze River region in southern Sichuan and northeastern Yunnan were established in the northern watersheds and river basins of mainland Southeast Asia. Whether already organized under separate "chieftains" (Chula Chakrabongse, 1960 : 17), or initially acephalous pioneer groups recognizing the leadership of village founders, they formed polities called myang (var., muang, muong, myng), under rule of hereditary sovereigns, or chao myang. Most northern myang constituted single upland valley jurisdictions, with a few exceptionally powerful chao controlling multi-valley systems. There is a correspondence between local topography and population distributions, but a conception of the myang as territorially-based polities obscures an important dynamic in the expansion of the Tai into mainland Southeast Asia and the centuries of conflict among various Tai powers. The myang is rather a "political entity of human settlements" (Davis, 1984: 82n), representing an hierarchical distribution of power focusing on a particular town, as the hub of a civil tradition and center of authority. Conflict among myang has, historically, assumed the aspect of competition for power over areas of habitation and not over land, itself. 

The particulars of early Tai expansion are largely undocumented. It is assumed transmission of chao authority, according to either ultimogeniture or primogeniture, encouraged a process of fission, with disinherited sons pursuing personal fiefs, perhaps through officially sanctioned and supported expeditions. ver occurring, it is apparent the Tai systematically settled new territories or consolidated non- Tai populated areas, proliferating first along the upland frontier in China and the Mon-Khmer and Burman "civilizations" of mainland east Asia, while rapidly encroaching on those southern domains. On the basis of historical chronicles, legends, and the contemporary situation, it is presumed Tai displaced and in some cases assimilated or co-opted aboriginal populations. 

The rise to power of the Mongols over Sung China and annexation of Yunnan Kublai Khan in the mid-thirteenth century precipitated a more dramatic Tai ,ion through the region. In the east, a group sometimes called the "Lesser Tai" Noi (distinguished from the western "Greater Tai" or Tai Yai, also called the Shan Tai) moved down the au River valley into the middle Mekhong, Plaines des Jarres and beyond. In the northern Menam Chao Phraya valley, two Tai governors of towns Khmer control rebelled and took control of the northern central plains Khmer hold at Sukhotai in 1238, founding a rule considered the precursor to the Siamese, or Thai, nation (Syamananda, 1981 : 20f[). During the reign of Sukhotai's Kamhaeng, several neighboring Tai chao widened their territorial domain. Chao Mengrai, in alliance with Rama Kamhaeng and Chao Khun Ngam Myang of Phayao, shed Lannatai which extended from the upper Chao Phraya valley to Wiengchan (Vientianne) on the middle Mekhong (Hall, 1981 : 186-190). In 1353 Chao Fa Ngum : Sawa (chao of what is now Luang Phrabang) brought Wiengchan and Luang 109 together as the centers of Lan Chang, around which the modern Lao -'s Democratic Republic is constituted. 

Flanked by the Mongols in the north and Viet to the southeast, the older myang between the Hong or Red River in the Tonkin and the Ou---an area referred to "central uplands" (Lebar et al., 1964 : 188)-were thus isolated by a succession stronger Tai myang in broader lowland valleys to the southwest. Among those .I myang,. expansionary fission gave way to a tendency to assert territorial I through intra-regional contest, often with the support of more powerful Tai successors. In addition, the frontier myang were repeatedly impressed by the lowland Tai military conflict against their neighbors.  

Upland and lowland Tai myang during the thirteenth century likely differed on1y in scale and political environment, but the dynamic of a more profound divergence was incipient within those disparate circumstances. Until the European colonial period, central upland Tai perpetuated the supposedly indigenous practices of hereditary rule and as decentralized states divided into classes based primarily on kinship, i.e., as feudal chiefdomships. Lowland myang governments, on the other combined elements of feudalism, military aristocracy, and civil bureaucracy, assimilating elements of their predecessors' politico-religious ideology and Indic traditions of statecraft (Coedes, 1966: 189-198). Supreme authority remained an hereditary office, and governorships in constituent myang were often held by either kin of the ruling chao or local vassal chao. Regions were also awarded to non-kin military leaders, and many levels of administration were dominated by commoners.

The unification of vast areas under centralized authority has frustrated Southeast Asian leaders into the modern era. Military expeditions against distant myang might result in imposition of nominal sovereignty, but states along the periphery of the major river basins and scattered among mountain valleys have been difficult to consolidate. In these outlying areas, vassal myang were sometimes virtually autonomous entities, or else disputed frontiers tributary to whichever regnant power. So it was among the central uplands. Long associated with the pre-colonial Lao states, the upland myang were under nominal Siamese hegemony in some periods, allied with Annam, China, or Burma in others. As Kunstadter observes, such marginal polities as in the central uplands which strove to preserve identity under threat of losing political independence to lowland powers sometimes erected "cultural boundaries" in ethnic opposition (1967 : 10). As a result of their contest by the Chinese, Burmese, Lao, Annamese, Siamese, and French, upland Tai "have come to be considered minority or tribal peoples, like the Lue, the Red Tai, White Tai, and Black Tai" (1967 : 11).