The battle allegedly took place in May 23, 844, during the Reconquista period, in the Campo de la Matanza, near Clavijo, La Rioja, Spain. The Christian forces were led by King Ramiro I of Asturias and General Sancho Fernández de Tejada.

Ramiro's Christian troops, led by Sancho de Tejada, went in search of the Muslims commanded by Abderramán II; but upon reaching Nájera and Albelda they would see themselves surrounded by a large Arab army made up of troops from the peninsula and levies from present-day Morocco, with the Christians having to take refuge in the Clavijo castle in Monte Laturce.

The chronicles say that Ramiro I had a dream in which the apostle Santiago (Saint James) appeared, promising victory.  The next day, May 23, 844, the armies of Ramiro I, encouraged by the presence of the warrior apostle mounted on a white steed, faced the Muslim army. 

After the victory, in honor of Saint James, Ramiro ordered the construction of the Church of the Blessed Santiago and granted Sancho certain privileges in addition to the surname Tejada in memory of the branch of a yew tree that he used as a weapon when his spear was broken in combat.

On May 25 in the city of Calahorra (the year is not specified), Ramiro dictated the vow of Santiago, committing all Christians of the Peninsula to make a pilgrimage to Santiago de Compostela, bringing offerings in gratitude to the Apostle for his intervention and imposing a mandatory tax on the Church.

With this event, the Apostle became a symbol of the fight against Islam, and since then he was recognized as Santiago Matamoros.

The first chronicle that cites the apparition of Saint James was narrated (around 1243) by Rodrigo Jiménez de Rada, archbishop of Toledo.^{[citation needed]}

In the legend, James, son of Zebedee, an Apostle of Jesus, suddenly appears and leads an outnumbered Christian army to gain its victory. He became the patron saint of Spain and is known to Spaniards as Santiago Matamoros ("the Moor-killer"). Aspects of the historical Battle of Monte Laturce (859) were incorporated into this legend, as Claudio Sánchez-Albornoz demonstrated in 1948.^[3]

The legend as it survives was first written down about 300 years after the supposed event on a spurious charter. Another item, a forged grant to the Church of Santiago de Compostela by which Ramiro reportedly surrendered a part of the annual tribute owed him by all the Christians of Spain, also dates from the mid-twelfth century. The history of the cult of Saint James is rich in such frauds.^[1] Historian Jean Mitchell-Lanham says, "While this event is based on legend, the supposed battle has provided one of the strongest ideological icons in the Spanish national identity."^[4]

Saint James' appearance at Clavijo has been a major theme in art. Among those artists who portrayed him there are Aniello Falcone, Paolo da San Leocadio, Evaristo Muñoz, Mateo Pérez, Martin Schongauer, Corrado Giaquinto, and Antonio González Ruiz.

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  Late medieval engraving of the battle of Clavijo by Martin Schongauer
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  Gable of the Pazo de Raxoi, Santiago de Compostela, Spain
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  Scenes from the life of Saint James, including the battle of Clavijo
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  Saint James appearing at Clavijo, by Antonio González Ruiz
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  St. James as carved by anonymous Mexican stone carvers. Santa Fe, New Mexico, United States 1760

• Cross of Saint James

• Pérez de Urbel, Justo. 1954. "Lo viejo y lo nuevo sobre el origin del Reino de Pamplona". Al-Andalus, 19:1–42, especially 20–6.
• Fletcher, Richard A. 1984. Saint James's Catapult: The Life and Times of Diego Gelmírez of Santiago de Compostela. Oxford: Oxford University Press.