Throughout history, marriages have been made solely for political reasons. For example, King John II of Castile married Maria of Aragon (sister to King John II of Aragon) to produce an heir to inherit the thrones of Aragon and Castile, therefore unifying the two regions.

          After her father, King John II of Castile died, Isabella was pressured by her brother King Henry IV to marry King Alfonso V of Portugal, but she refused to, knowing that the nobles did not approve of Henry.

          She secretly sent out a member of the royal court to look for suitors for her. He brought back news of Ferdinand, the handsome, young prince of Aragon. Isabella gained support for this marriage as it would bring unity between the two kingdoms of Castile and Aragon, perhaps even unifying the whole of Spain one day. They married four days after they met.

Marriage: Bonding two areas, and two lives

       Diplomatically, Ferdinand held less power because Aragon was much smaller then Castile. But privately, Isabella assured him that they would make decisions together and developed the motto, "the one as much as the other". Their marriage was at first political, but they grew to love and trust each other.

         Ferdinand inherited Aragon in a stable condition thanks to the efforts of his father. However, Castile was in chaos; the previous kings (John II of Castile and Henry IV) had not properly managed affairs, leaving the area with a high crime rate, different laws in every other town, and there was not even a common currency.

       In Castile, the nobles held the power. Each area had their own set of laws; however, groups of people called hermandades acted as law enforcers. The nobles kept money for themselves, sucking the royal treasury dry. This also meant that most of the population were poverty-stricken. With no stable central government, trade, agriculture, and infrastructure were practically nonexistent.
       With many more problems, the marriage of Ferdinand and Isabella had already formed a partnership with a daunting task of rebuilding the corrupt, separate area of Castile.