 Once the Castilian and Aragonese military confirmed their occupation of all the strongholds, the ground was paved for a progressive institutional takeover marked by the centralizing drive of the Spanish-Castilian Crown.This was the source of frequent frictions and tensions.The diplomat and writer Niccolò Machiavelli anticipated a prompt and easy understanding by Ferdinand II with France "on the only condition of keeping Navarre, giving up instead the Duchy of Milan for its vicinity to the Helvetians."