There should definitely be cultural conversion of some sort. Though I would prefer a, maybe temporary and transitionary, hybrid culture. Thus, when France conquers England in 1700, 50 (or 100 or more) years later there is an Anglo-French culture. Also, there is a lot of confusion over nationality, culture and ethnicity. We could debate endless over precise definitions of these terms but I've always thought that ethnicity refered to one's genetic lineage, thus, the Irish people are ethnically Irish (or Celto-[Unknown Neolithic People] whatever) but some ethnic Irish are English (or American or wherever else the Irish are) culturally, in that they are part of that greater cultural body. Culture is hard to define, but I usually think that it's related more to language than anything else. (Although they're not equivalent as they would mean that English and American culture are the same) As for nationality, it seems that it is equivalent to a combination of culture and religion (and maybe language). Regardless, cultural conversions did indeed happen historically. As in the case of Ireland, much of non-langue d'oil France, and the Arabization of the Middle East and North Africa.