Portugal–Spain border

A medieval line

The first overall border agreement, the Treaty of Badajoz, was reached on 16 February 1267 between the king of Portugal and his father-in-law, Alfonso X of Castile. On 12 September 1297 King Dinis of Portugal and Fernando IV of Castile and León signed the Treaty of Alcañices, a treaty of peace and frontiers, and the line it describes is practically the same as today’s.^[1]

Alcañices also confirmed Portugal’s possession of the Algarve and made an alliance between the two kingdoms.^[3] Spain did take over all of Portugal from 1580 to 1640, but the frontier outlived that union.^[2]

Surveyed in the 19th century

A joint Spanish–Portuguese commission was set up in the 1850s to fix the line from the mouth of the Minho to where the Caia meets the Guadiana, near Badajoz. Its fieldwork, led by military engineers, lasted until 1861, and the Treaty of Limits was signed in Lisbon on 29 September 1864.^[1]

The treaty also tidied up old oddities. In the north it drew the line through the Couto Mixto, and Portugal renounced whatever rights it had over that land and its villages, which became Spanish.^[4] The line was marked with pillars numbered 1 to 801, and the general demarcation act was approved by an exchange of notes on 1 December 1906.^[1]

“Portugal renuncia en favor de España a todos los derechos que pueda tener sobre el terreno del Coto mixto”^[4]

The Guadiana and Olivenza

In 1801 France and Spain invaded Portugal, and Spanish troops under Manuel de Godoy took the town of Olivenza (Portuguese: Olivença). In the Peace of Badajoz that June, Portugal ceded Olivenza to Spain.^[5] The town lies on the east bank of the Guadiana.^[2] The episode is known as the War of the Oranges, after the oranges Godoy picked at nearby Elvas and sent to the queen of Spain.^[5]

The southern stretch was settled by the Convention of Limits of 29 June 1926, which runs from the confluence of the Cuncos with the Guadiana, south of Olivenza, to the sea, with markers numbered 904 to 1,048.^[1] Neither treaty covers the stretch between the Caia and the Cuncos, where the river passes Olivenza.^[1]

Portugal has never quite given up its claim to Olivenza. In 2004 The Irish Times reported that Lisbon did not accept the Guadiana there as the frontier, while a senior Spanish diplomat called handing the town back “unthinkable”. Neither government wanted the dispute to get out of control, and a new bridge had just linked Olivenza with Elvas across the river.^[2]