Concept and duration
Traditional historiography has stressed since the 19th century the existence of the Reconquista, a continuous phenomenon by which the Christian Iberian kingdoms opposed and conquered the Muslim kingdoms, understood as a common enemy who had militarily seized territory from native Iberian Christians.
The concept of a Christian reconquest of the peninsula first emerged, in tenuous form, at the end of the 9th century. A landmark was set by the Christian Chronica Prophetica (883–884), a document stressing the Christian and Muslim cultural and religious divide in Iberia and the necessity to drive the Muslims out.
Both Christian and Muslim rulers fought amongst themselves. Alliances between Muslims and Christians were not uncommon. Blurring distinctions even further were the mercenaries from both sides who simply fought for whoever paid the most. The period is seen today to have had long episodes of relative religious tolerance.
The Crusades, which started late in the 11–12th century, bred the religious ideology of a Christian reconquest, confronted at that time with a similarly staunch Muslim Jihad ideology in Al-Andalus by the Almoravids, and to an even greater degree by the Almohads. In fact, previous documents from the 10th and 11th centuries are mute on any idea of "reconquest". Propaganda accounts of Muslim-Christian hostility came into being to support that idea, most notably the Chanson de Roland, a fictitious 11th-century French version of the Battle of Roncevaux Pass (778) dealing with the Iberian Saracens (Moors), and taught as historical fact in the French educational system since 1880.
The modern idea of the earlier concept of Reconquista is inextricably linked to the foundational myths of Spanish nationalism in the 19th century, and consolidated by the mid-20th century during Franco's National-Catholic dictatorship, based on a strong underlying Castilian ideological element. The idea of a "liberation war" of reconquest against the Muslims, depicted as foreigners, suited well the anti-Republican rebels during the Spanish Civil War who agitated for the banner of a Spanish fatherland threatened by regional nationalisms and communism. Their rebellious pursuit was thus a crusade for the restoration of the Church's unity, where Franco stood for both Pelagius of Asturias and El Cid.
Some contemporary authors consider it proved that the process of Christian state-building in Iberia was indeed often defined by the reclamation of lands that had been lost to the Moors in generations past. In this way, state-building might be characterised—at least in ideological, if not practical, terms—as a process by which Iberian states were being 'rebuilt'.. In turn, other recent historians dispute the whole concept of Reconquista as a concept created a posteriori in the service of later political goals. A few historians point out that Spain and Portugal did not previously exist as nations, and therefore the heirs of the Christian Visigothic Kingdom were not technically reconquering them, as the name suggests. One of the first Spanish intellectuals to question the idea of a "reconquest" that lasted for eight centuries was José Ortega y Gasset, writing in the first half of the 20th century. However, the term is still widely in use.