The Alhambra Decree, formally known as the Edict of Expulsion, was a significant mandate enacted by Queen Isabella I of Castile and her husband King Ferdinand II of Aragon. It required the conversion of all Jewish and Muslim subjects in their territories to Christianity by a specified deadline, which was set for August 2 of that year, or face expulsion from their homeland. This proclamation came on the heels of the successful completion of the Reconquista, the centuries-long effort to reclaim the Iberian Peninsula from Muslim rule, which culminated with the fall of Granada in 1492.

The motivations behind this decree were complex. Isabella and Ferdinand were keen on consolidating their newly unified kingdom and saw religious homogeneity as a path toward achieving that goal. Additionally, the monarchy sought to eliminate what they perceived as the influence of unconverted Jews and Muslims, who had coexisted with Christians for centuries. By compelling conversion, the Catholic Monarchs believed they could foster a more cohesive national identity, even as historical precedents suggested that such measures would lead to greater societal strife and division.

The consequences of the Alhambra Decree were immediate and severe. Approximately 150,000 Jews abandoned their homes, fleeing to various countries in Europe and North Africa. Those who remained were often forced to convert, facing suspicion and discrimination. The decree dramatically altered the demographic and cultural fabric of Spain, leading to the eventual decline of its Jewish and Muslim communities, and it set a precedent for future intolerance and persecution against non-Christian populations across Europe.