The Reconquista was a period of nearly 800 years (between 722 y 1492) during which several Christian kingdoms of the Iberian Peninsula succeeded in retaking (and repopulating) the Iberian Peninsula from the Muslim Al-Andalus Province.
The Islamic conquest of the Christian Visigothic kingdom in the eighth century (begun 710–12) extended over almost the entire peninsula (except major parts of Galicia, the Asturias, Cantabria, Catalonia and the Basque Country). After 500 years, in the thirteenth century, the sole remaining Moors ruling were the Nasrid dynasty in the Kingdom of Granada. They were defeated in 1492, which brought the entire Iberian Peninsula under Christian rule, thus completing the Reconquista.
The Reconquista of Al-Andalus began soon after the Islamic conquest and passed through major phases over the centuries before its completion. The formation of the Kingdom of Asturias under Pelagius and the Battle of Covadonga in 722 were major formative events. Charlemagne (768–814) reconquered the western Pyrenees and Septimania and formed a Marca Hispanica to defend the border between Francia and the Muslims. After the advent of the Crusades, much of the ideology of Reconquista was subsumed within the wider context of Crusading. Even before the Crusades, however, soldiers from elsewhere in Europe had been travelling to Iberia to participate in the Reconquista as an act of Christian penitence.
Christian and Muslim rulers commonly became divided amongst themselves and fought. Alliances across faith lines were not unusual. The fighting along the Christian-Muslim frontier was punctuated by periods of prolonged peace and truces. Blurring matters even further were the mercenaries who simply fought for whoever paid most.
The Reconquista was largely completed in 1238, when the sole remaining Muslim state on Iberia, the Emirate of Granada, became a vassal state of the Christian Crown of Castile. This arrangement lasted for 250 years until the Castilians launched the Granada War of 1492, which finally expelled all Muslim authority from Spain. The last Muslim ruler of Granada, Muhammad XII, better known as King Boabdil, surrendered his kingdom to Isabella I of Castile, who with her husband Ferdinand II of Aragon were known as the Catholic Monarchs (los Reyes Católicos).
Around 718 Pelagius (or Pelayo in modern Spanish), a Visigothic noble, began a rebellion against Munuza, a local Muslim governor. Becoming a local rebel leader he gathered all available support and one of his most important allies was Duke Pedro of Cantabria.
This battle, at the time probably considered little more than a small skirmish against local rebels would be considered by later Christian historians as the starting point of the Reconquista. The date and circumstances of this battle are very unclear, with several sources giving different dates. It is possible that the rebellion of Pelagius unfolded precisely because the greater part of the Muslim forces were gathering for the invasion of France, that it unfolded during this invasion, or even a bit later as the battered and weakened expedition returned and all available garrisons and reinforcements were probably re-called to bolster the army for its new invasion attempt.