Batavianization or Batavianisation (see -ise vs -ize) also known as Dutchification and; historically, as Belgianization, is the spread of the Dutch language, people and/or culture either by force or assimilation. In Dutch it is known as vernederlandsing or neerlandisatie.
The term Batavianization, derives its name from the Batavi, a Germanic tribe living in the Netherlands, and long regarded as the mythical ancestors of the Dutch people. The term Dutchification is mostly used in English publications by Dutch authors, less so by native English-speakers. This likely has to do with the fact that Dutch isn't a Latin-derived term and hence sounds somewhat childish to some ears in combination with the (Latinate) suffix -fication. As for Belgianization, Belgae was the standard term in Latin to refer to the Dutch (compare the Leo Belgicus, United Belgian States and Belgic Confession for example) in the Late Middle Ages. After the establishment of Belgium, its use generally shifted to mean Belgicism.
In the Netherlands, most of the Batavianization was of a linguistic and, to a lesser extent cultural nature, and was focused on the Frisian region. Beginning at the end of the migration period, Dutch nobles sought to conquer the Frisian lands, in which they largely succeeded around the end of the High Middle Ages. The conquest was gradual and moved from the West to the East. By the time the Frisian heartland (the modern province of Friesland) was conquered, many Frisians formerly living in West Frisia had already fled and the region was subsequently colonized by Dutch settlers. In the remaining Frisian territory, a ruling Dutch upper class was instituted, the legacy of which can still be found in Stadsfries. The West Frisian language has since adopted large amounts of Dutch vocabulary, to such an extent that many objects or concepts originating after the Dutch conquest are nearly all calques or loanwords from Dutch.
Despite Batavianization and the general idea that Frisians were underdeveloped and rural, Frisians never were the subject of ethnic discrimination or willful linguistic or cultural oppression.
Between the 1950s and early 1980s, primarily due to migration of rural West Frisian speakers to the non-West Frisian urban areas, and the settling of Dutch speakers from outside the province in the Frisian countryside, the percentage of inhabitants of Friesland using West Frisian as their home language dropped from 71% to 59%. The West Frisian language itself gradually dutchified as well.
A 2016 Radboud University Nijmegen study by linguist Geert Driessen showed that the percentage of West Frisian speakers steadily declined between 1994 and 2014 in favour of Dutch. During those twenty years, the number of West Frisian-speaking children within families decreased from 48% to 32%, and outside families (amongst their friends) from 44% to 22%. The percentage of parents talking West Frisian amongst themselves dropped from 58% to 35%. According to Driessen, 'in two generations, there won't be much left', because people will no longer be able to read and especially write in West Frisian. The Dutch language would hang on for a few generations longer than West Frisian, but Driessen expects 'everything to switch to English.'
In Belgium, batavianization was an essential part of the political objectives of the Flemish movement, a social movement seeking acknowledgement of the Dutch language and culture. When Belgium was established in 1830, the Francophone government oppressed the Dutch populace. Dutch was banned from higher education, politics and justice in favour of French. Hence Batavianization in Belgium largely refers to the process of replacing French as the language of education in universities and as the language of culture among the elite.
For the concept of "Batavianization" in colonial North America, see:
For the concept of "Batavianization" in colonial Dutch East Indies, see: