Treaty of Badajoz (1267)
The Treaty of Badajoz was signed in Badajoz on February 16, 1267 between King Alfonso X of Castile and King Afonso III of Portugal. Both signatories agreed to establish lines of mutual assistance and friendship. Based on the terms of the accord, Alfonso X surrendered all rights to the Kingdom of the Algarve, which included the service of fifty knights. Moreover, he commanded his lieutenants to surrender the castles they controlled in Algarve to the Kingdom of Portugal. Despite all this, Alfonso X still continued to use the title king of the Algarve even though it was probably used in reference to the territory of Niebla. Both signatories agreed to use the Guadiana River from Elvas and Badajoz to Ayamonte on the Atlantic Ocean as the boundary line separating Castile and Portugal. This, in turn, forced Portugal to surrender Aracena, Moura, Serpa, and Aroche located east of the boundary line. North of the boundary line, Portugal was able to maintain Arronches, Alegrete, and Elvas, but was forced to capitulate Valencia de Alcántara and Marvão.
- O'Callaghan, p. 369. "The kings of Castile and Portugal met at Badajoz on 16 February 1267 to conclude a treaty of peace, promising mutual friendship and assistance. Out of love for his grandson, and in gratitude for the aid given by the king of Portugal during the revolt of the mudéjares, Alfonso X yielded all rights to the Algarve, including the service of fifty knights, and instructed his lieutenants to surrender to Portugal the castles they held for him in the Algarve. This was an absolute cession of Castilian rights to the Algarve, though Ballesteros suggested that by continuing to use the title "king of the Algarve," Alfonso X sought to keep alive some vestigal claim to suzerainty; he might have used the title, however, with reference only to the territory of Niebla. The two kings also agreed upon a delimitation of their borders, with the river Guadiana from Elvas and Badajoz to Ayamonte on the Atlantic Ocean as the dividing line. In effect, Portugal surrendered Aroche, Aracena, Moura, and Serpa east of that line; to the north of Elvas, Arronches and Alegrete remained to Portugal, while Marvão and Valencia de Alcántara were adjudged to Castile. As a result of this agreement, Portugal attained substantially the frontiers she has today, with the exception of the districts of Moura and Serpa and of Riba-Coa, including the towns of Almeida, Vilar Maior, and Alfaiates; these were incorporated subsequently into the kingdom during Dinis's reign."
- O'Callaghan, Joseph F. A History of Medieval Spain. Cornell University Press, 1983. ISBN 0-8014-9264-5