Treaty of Zamora (1143): Portugal Becomes a Kingdom

The Treaty of Zamora, agreed on 4–5 October 1143, is traditionally regarded as the birth certificate of Portugal as an independent kingdom. At a meeting in the Leonese city of Zamora, Alfonso VII of León and Castile accepted that his cousin Afonso Henriques could rule Portugal with the title of king. The agreement turned a frontier county into a kingdom that has kept largely the same borders on the Iberian mainland since the 13th century.

Background: the County of Portugal

At the end of the 11th century the land between the Minho and Mondego rivers was a county within the Kingdom of León. In 1096 King Alfonso VI gave it to Henry of Burgundy, a French knight who had married his illegitimate daughter Teresa. Henry ruled as count under Leonese overlordship.

After Henry died in about 1112, Teresa governed the county for their young son, Afonso Henriques. She increasingly relied on Galician nobles, which angered the Portuguese aristocracy. On 24 June 1128, at the Battle of São Mamede near Guimarães, Afonso and his supporters defeated his mother’s party and he took control of the county.

From count to king

Afonso spent the next decade fighting on two fronts. To the north he clashed with his cousin Alfonso VII, who had been crowned “Emperor of all Spain” in 1135 and claimed authority over the other Christian rulers of Iberia. In 1137 they made peace at Tui, but fighting soon resumed.

To the south lay the Muslim lands of al-Andalus, then under the Almoravids. On 25 July 1139 Afonso won a victory at Ourique, in the south, the exact location of which is still debated. Later legend added a vision of Christ before the battle, but this story appears centuries afterwards. From around 1139–1140 Afonso began to use the title rex, king, in his documents.

The meeting at Zamora

The conflict between the two cousins was mediated by the papal legate, Cardinal Guido de Vico, who had come to Spain to hold church councils. In early October 1143 Afonso Henriques and Alfonso VII met at Zamora in his presence.

Alfonso VII agreed to recognise Afonso’s royal title. In return, according to the usual interpretation, Afonso accepted a form of honorary subordination to the emperor, who already counted other kings among his vassals, and received the lordship of Astorga in León. No formal document of the treaty survives, so the precise terms are uncertain.

What mattered most was the recognition of kingship. A king was in principle no longer simply a count serving a greater lord, and Portugal’s ruler could deal with other powers on more equal terms. The legate’s presence gave the meeting the weight of the Church, which Afonso hoped to turn into firmer support from Rome.

For Alfonso VII the settlement was also useful. It ended a costly border war and allowed him to concentrate on his own campaigns against al-Andalus, while preserving the idea that he stood above the other Christian kings of the peninsula.

Seeking the pope’s approval

On 13 December 1143 Afonso wrote to the papacy in a letter known from its opening words as Claves regni. He declared himself a vassal of the Holy See and promised an annual tribute of four ounces of gold. Placing the kingdom under the pope’s protection was intended to guard it against any future Leonese claims.

The papacy accepted the tribute but was cautious, at first addressing Afonso only as duke. Full recognition came on 23 May 1179, when Pope Alexander III issued the bull Manifestis probatum, confirming Afonso as king and his kingdom’s independence, partly in recognition of his wars against the Muslims.

Consequences

With his position secured, Afonso turned south. In 1147 he captured Santarém and then, with the help of northern European crusaders on their way to the Second Crusade, took Lisbon after a siege of about four months. These conquests moved the centre of Portugal southwards. The Reconquista, which had gained a major symbolic boost with the capture of Toledo by Castile in 1085, now had a second western front.

Later Portuguese rulers continued the advance, completing the conquest of the Algarve in 1249. The Treaty of Alcañices of 1297 with Castile fixed a border that has changed little since.

Timeline

• 1096: Henry of Burgundy receives the County of Portugal from Alfonso VI.
• 24 June 1128: Afonso Henriques wins the Battle of São Mamede and takes control of the county.
• 1137: Peace of Tui between Afonso and Alfonso VII.
• 25 July 1139: Afonso defeats Muslim forces at the Battle of Ourique.
• 4–5 October 1143: Alfonso VII recognises Afonso as king at Zamora.
• 13 December 1143: Afonso places Portugal under papal protection.
• 1147: Portuguese and crusader forces capture Lisbon.
• 23 May 1179: Pope Alexander III recognises Afonso as king in Manifestis probatum.

Why it matters

Zamora marks the moment when Portugal’s separate existence was accepted by its most powerful neighbour. Together with the papal bull of 1179, it laid the foundations of one of Europe’s oldest nation-states, whose borders have remained remarkably stable for more than seven centuries.