The threat of internal stability remained until the marriage of Queen Isabella I of Castile and King Ferdinand II of Aragon in 1469. The two monarchs were promptly challenged by Joan of Castile but were swiftly successful. Isabella would go on to establish the "Hermandad" militia system, which would provide her with a royal counterbalance to any future challenge from the nobility. The two monarchs proceeded to conquer the Kingdom of Granada, the last Islamic state in the Iberian peninsula, which was completed by 1492. In that same year, the Alhambra Decree was issued, expelling all Jews from both Castile and Aragon. Now unified, Spain now enjoyed relative internal stability; rights and lands across the Mediterranean; and a strong tradition of seafaring in both the Atlantic and Mediterranean, which it would maximise in the coming decades.