A process of political conglomeration among the Christian kingdoms also ensued, and the late 15th-century saw the dynastic union of Castile and Aragon under the Catholic Monarchs, sometimes considered as the point of emergence of Spain as unified country. The Conquest of Navarre occurred in 1512. There was also a period called Iberian Union, the dynastic union of the Kingdom of Portugal and the Spanish Crown; during which, both countries were ruled by the Spanish Habsburg kings between 1580 and 1640.