Although the vast majority of Spain's 250,000 "conversos" had abandoned Judaism and been assimilated into Spain's dominant Catholic culture, many of those continuing to secretly practice their former religion felt threatened and persecuted by the Inquisition which continued to actively persecute heresy. Some of these chose to leave Spain, in bands or as individual refugees. Many migrated to Italy, attracted by the climate, which resembled that of the Iberian Peninsula, and by the kindred language. When they settled at Ferrara, Duke Ercole I d'Este granted them privileges. His son Alfonso confirmed the privileges to twenty-one Spanish "conversos": physicians, merchants, and others (ib. xv. 113 et seq.). A thoroughly researched history of these migrations is also contained in the book about one of their leaders called, "The Woman Who Defied Kings", by the historian and journalist Andree Aelion Brooks.