River Delta by descendants of Chinese immigrants, and later was absorbed into the co-existing Việt-Mường languages by the ninth century. Phan identifies three layers of Chinese loanwords into Vietnamese: the earliest layer of borrowing dates to the Han dynasty (ca. 1st century CE) and Jin dynasty (ca. 4th century CE); the late layer of borrowing dates to the post-Tang period, and the recent layer of borrowing dates to the Ming & Qing dynasties. National historiography Study of Northern Vietnam and the Red River Delta during the first millennium AD is highly problematic. This region is widely associated with the foundation of the modern country and nation-state of Vietnam. It has been given exceptional treatment and academic scrutiny compared to other regions. This unique academic focus has resulted in critical misinterpretations. Some notable academic works have echoed the established frameworks of colonial and postcolonial Vietnamese nationalist historiography in order to associate the entire history of the early Red River Delta with the Vietnamese, i.e. the Kinh, and the modern country of Vietnam. The rewriting of Vietnamese history in the 20th century considered pushing several nationalistic themed theories. On notable theory, the Continuity, is defined as a belief that the peoples of Red River Delta during Han-Tang period had always retained their unique "Vietnamese identity" and "Vietnamese spirit", which was arguably rooted in the highly sophisticated Van Lang kingdoms under the Hung kings, which were largely legends transformed into "historical facts" under the scholarship of the Democratic Republic of Vietnam. This was despite relentless Chinese acculturation, making them "different" from other groups in Southern China who "eventually lost their separate identities through assimilation to Chinese culture." The Continuity theory reconstructs the emergence of the Đại Việt kingdom in the 10th century as the awakening and resurrection of "Vietnamese sovereignty," and these traditions of Vietnamese exceptionalism continued into modern Vietnam. For example, Keith Taylor took up some aspects of Vietnamese nationalist historiography in his 1983 monograph, The Birth of Vietnam, and falsely asserted that "Vietnam's independence resulted from a thousand-year struggle to throw off Chinese rule by a group of people who held a conviction 'that they were not and did not want to become Chinese.'" Later, Taylor retreated from Vietnamese nationalist historiography. No evidence of "ethnic Vietnamese" resembling what would be considered the modern Vietnamese exists during the Han-Tang period. Instead, ancient Northern Vietnam as well as today was very diverse and