To suggest that Isabella was successful from the outset in securing the Castilian crown and the support of its people would be a foolish interpretation. It took ten years before she was fully accepted as rightful ruler, during which time a number of important factors developed that today can be seen as the clearest reasons for her success. Paramount among these was her determined, intellectual and shrewd personality and character. Without these traits, the other factors would have been irrelevant.

In October 1469, Isabella was married to Ferdinand of Aragon. What is interesting here is the terms of the treaty drawn up after the ceremony that both of them signed. It claimed Isabella to be the rightful and true heir of Castile, that their children were to be educated in Castile and that Ferdinand was to have no power in Castile, just as Isabella was to be impotent in...