Prussia did not takeover Brandenburg though, just the name did, if anything one could construe the union as a second Germanization of Prussia, bringing it formally into German affairs and wider Protestant world and detaching it from Poland(even if Prussia converted by itself)Prussia is actually an perfect example-- it was a German settler colony.
Interesting, what is this theory?If Italo-Celtic theory is true,then The ones who branched out to colonize Italia eventually conquered Celtic inhabited lands.
Italo-Celtic theory just says that the 2 groups were ancestrally related to a degree stronger than just general Indo-European or whatever other inbetween ancestry there was between European IE languages.Interesting, what is this theory?
The various Italic tribes seem to be the result of a Late Bronze Age/Early Iron Age invasions from Central Europe, yes (with Etruscans as the survivors for a while, and Messassipii and other southeasterners being Illyrians who crossed Adriatic), but all of this seems to happen pre-Celtic ethnogenesis... (The first mention of Celts seem to be from 700-800BCE or so, when a contingent of them cross Pyrenees and conquered central Iberia to become the Celtiberians)