Torben S. Hansen :
'Non sufficit orbis - Castile and the Spanish Empire 1492-1659'

The Iberian peninsula was politically divided in the medieval epoch, but in 1469 a marriage between Isabel and Fernando, heiress and heir to the crowns of Castile and Aragon respectively, prepared the dynastic union of their realms. Hailed as los Reyes Católicos the couple thrust Spain into an unprecedented expansion in Europe and "the new world" beyond the ocean. Thus - to quote the historian Henry Kamen - the "nation was caught up unexpectedly into a global role for which it was never adequately prepared and which it made heroic efforts to fulfil, with consequences that altered the face of world civilisation..."