Relations between Portugal and Castile in the Late Middle Ages – 13th-16th centuries

A study of the intense diplomatic relations maintained between the Portuguese and Leonese, afterwards Castilian-Leonese, monarchies throughout the Middle Ages. They were dotted with a series of agreements relating to the internal problems of each kingdom, the mutual relations and the general political situation in the Iberian Peninsula. These relations, except for specific moments of brief warfare, which were sometimes very serious, were friendly and familiar. This didn’t exclude the occurrence of frictions resulting from contrary interests. On both sides of the frontier very similar problems were faced: dynastic confrontations or rebellions of the nobility in which both monarchies usually collaborated closely. Castilian expansion and the resulting imbalance of power in its favour, was the cause of the gravest tensions.