According to Jennifer Holmgren, the first six centuries of Chinese rule in Vietnam “saw more ‘Vietnamization’ of local Chinese than Sinicization of the indigenous Viets”. Many Chinese clans "settled into, helped modify, and were finally absorbed into the social, economic and political environment in Northern Vietnam". C. P. FitzGerald also concluded after showing various evidence that the Chinese troops and migrants became absorbed into and assimilated with the native people in Vietnam. Confucianism has helped to advance the frontiers of Vietnam and create a reasonable platform “where the Vietnamese people gained a national identity which made further Chinese intrusion improbable, rare, and finally wholly discontinued”. A similar claim can be found in Joseph Buttinger's work, where Confucianism failed to Sinicize the local Vietnamese. He asserted that “the more they (Vietnamese) absorbed of the skills, customs, and ideas of the Chinese, the smaller grew the likelihood of their ever becoming part of the Chinese people”. The strength of localization in ancient Vietnam has thus been widely noted.