On October 19, 1469, Ferdinand of Aragon marries Isabella of Castile in Valladolid, thus beginning a cooperative reign that would unite all the dominions of Spain and elevate the nation to a dominant world power. Ferdinand and Isabella incorporated a number of independent Spanish dominions into their kingdom and in 1478 introduced the Spanish Inquisition, a powerful and brutal force of homogenization in Spanish society. In 1492, the reconquest of Granada from the Moors was completed, and the crown ordered all Spanish Jews to convert to Christianity or face expulsion from Spain. Four years later, Spanish Muslims were handed a similar order. In 1492, Christopher Columbus, an Italian explorer sponsored by Isabella and Ferdinand, stumbled upon the Americas for Europe and claimed the territory for Spain. Ferdinand and Isabella’s subsequent decision to encourage vigorous colonial activity in the Americas led to a period of great prosperity and imperial supremacy for Spain.