With the marriage of the heirs apparent to their respective thrones Ferdinand of Aragon and Isabella of Castile created a personal union that most scholars[citation needed] view as the foundation of the Spanish monarchy. The union of the Crowns of Castile and Aragon joined the economic and military power of Iberia under one dynasty, the House of Trastmara. Their dynastic alliance was important for a number of reasons, ruling jointly over a number of kingdoms and other territories, mostly in the western Mediterranean region, under their respective legal and administrative status. They successfully pursued expansion in Iberia in the Christian conquest of the Muslim Emirate of Granada, completed in 1492, for which Valencia-born Pope Alexander VI gave them the title of the Catholic Monarchs. Ferdinand of Aragon was particularly concerned with expansion in France and Italy, as well as conquests in North Africa.[14]