The Arrival of the Moors.
Hidden in some bushes outside the walls of Toledo, a young man watches a beautiful young woman as she bathes in the river Tagus, Eventually overcome by passion, he seduces her. She complains to her father who is the governor of the far away outpost of Ceuta, across the straits from Gibraltar.
The father, angered, seeks vengeance and invites the expansionist Muslim forces of North Africa to invade his country and punish the man who has offended him. That man was Roderic (Rodrigo), the last king of the Visigoths, the young woman is known to us as Florinda (or La Cava), daughter of a Visigoth noble, Count Julian.
Desire, anger, revenge…a potent combination. It’s not the first time that unrestrained passion has had far reaching consequences, and nothing is likely to give a greater human edge to the fall of kings or a kingdom than the weakness of the flesh.
It is a compelling story as the explanation for the invasion of the Moors, but it is no more than that, a story embroidered by later generations to explain why Christian Hispania (modern Spain and Portugal) was lost to the Muslims.
It isn’t the only tale. Another has a more prophetic ring. A certain king of Spain had deposited in a tower an urn containing a parchment. He sealed the tower with a padlock and imposed on his successors, each in turn, the obligation of respecting the integrity of the tower and of adding another padlock to its door.
All did so except Roderic. He ordered all the padlocks removed, and entered to the innermost room of the tower. There he saw painted on the walls figures of Arab horsemen bearing scimitars and lances. Opening the urn, he read what was written on the parchment: that whenever the tower was violated the country would be invaded and conquered by the people painted on the walls.
Legends are always later accretions, when chronological distance allows the imagination to weave tales around the historical skeleton. Unfortunately, we have no contemporary sources to balance the legendary versions, the closest being a Latin document called the Chronicle of 754 (after the the latest year recorded in it). It gives a sketchy outline of the events, but the reasons why the invasion took place and how it was carried out are largely conjectural.
The historical circumstances: What we know of the Muslim invasion.
What we do know is that in 711 an invading force of Muslims, led by a general named Tariq ibn Ziyad, landed near Gibraltar. In the following year, Tariq’s forces engaged Roderic and his army somewhere in the hills behind Tarifa or along the Guadalete River in the western part of the region we now know as Andalusia. Roderic was defeated and presumably killed (nothing more is known about him).
After Roderic’s defeat, the Muslim armies (now reinforced by more soldiers from across the straits of Gibraltar) faced little opposition as they moved rapidly north. There was some urban defiance –Mérida in particular, Córdoba, Zaragoza– which appears to have cost their inhabitants dearly, and was probably a disincentive for others to follow suit. But equally productive and less demanding, since it did not require the establishment of garrisons, was a peaceful agreement between the conquerors and conquered.

A case in point is a treaty arranged with a certain Theodemir, the Visigoth chief of Murcia. In return for submission, he retained his leadership and his people were free to follow their Christian practices. Furthermore, the Christians were required to refrain from helping deserters or enemies, and were obliged to pay individually an annual tribute of money and goods to the invaders.
By 720, the Muslims were in control of all of Hispania, except for a narrow strip along the north coast. They even penetrated north of the Pyrenees and caused havoc in southern Gaul (now the south of France) where they expended a great deal of energy over the next 15 to 20 years. Defeat at Poitiers at the hands of Charles Martel (the Hammer) in 732 was a setback, but it did not signal withdrawal from the south of Gaul. That took place a few years later and owed as much as anything to internal disputes within al-Andalus.
An overview of al-Andalus.
The invading forces were made up mainly of Berber tribesmen from the Maghreb (the north west of Africa), under Arab leadership. United by their religion, the two groups plus other Muslim soldiers –Egyptians, Syrians– are now generally lumped under “Moors,” and the territory they conquered they called al-Andalus, the southern part of which we now know as Andalusia.
http://en.wikipedia.org/wiki/Al-Andalus
From the 8th century to the 11th century, al-Andalus covered most of the Iberian peninsula, and then gradually contracted in the face of Christian expansion until, by mid way through the 13th century, all that was left was a strip about 100 kilometres wide (constituting the minor state or taifa of Granada) running along the south coast between Almería and Algeciras.
By the 16th century the Christian conquest of the peninsula was complete and al-Andalus was no more. Ironically, however –in view of its demise—al-Andalus left a linguistic heritage in the name of what is the best known and most visited area of Spain: Andalusia.
The changing face of Islam in the Iberian Peninsula can be divided into three general stages, each of which is encapsulated in the fortunes of three cities: Córdoba, Seville and Granada. Córdoba was pre-eminent in the first stage (extending roughly from 756 to 1031), the end of which was marked by political fragmentation into several taifa or minor states. Of these numerous minor states, that of Seville –present-day capital of the autonomous region of Andalusia– shone as the political and cultural centre.
There was a hiatus between 1085 (when the taifa of Toledo fell to Alfonso VI, King of the Christian kingdoms of León and Castile) and 1212, during which two fundamentalist groups from the Maghreb, the Almoravids (1086-1145) and the Almohads (1145-1212), successively exerted control over al-Andalus.

In 1212, the Almohads were defeated at the Battle of Las Navas de Tolosa in the Sierra Morena, the mountain range that separates Andalusia and Castile. Quickly other cities fell (Valencia, Murcia, Badajoz, Mérida, and finally in 1248 Seville), leaving only the taifa of Granada, which managed to retain its independence until the fateful year of 1492. After that, al-Andalus was no more.Nevertheless, we can add a fourth stage to the changing fortunes of Islam in Spain. Although Spain in the sixteenth century was nominally Christian, large numbers of “converted” Muslims, isolated in the mountains of the south or scattered through the regions of Valencia and Aragón, retained their Islamic practices. These converted Muslims, known as Moriscos, were eventually expelled by decree in 1609, thus bringing to a sad end a major experience in multicultural coexistence.
Postscript: Is al-Andalus relevant today?
Nowadays, if you ask Muslims who know something about the history of al-Andalus how they feel about it, some will admit to a nostalgic yearning for the return of Islamic Spain.
There are Muslims from many countries now living in Spain, but there are also former Spanish Catholics who have converted to Islam, claiming to have recovered their Muslim roots (others make no such claim but, disenchanted with Christianity, have found new faith in the Qur’an). The converts are mostly concentrated in the Granada, Córdoba, and other Andalusian communities, and on the whole seek to live peacefully with their Christian neighbours.
However, since September 11, 2001, and more specifically for Spaniards, since the Madrid subway bombings of March 11, 2004, attitudes towards Muslims have hardened, as they have in Western or Christian dominated countries in general.
Where the question: “Is al-Andalus relevant today?” becomes particularly pertinent is in the expressly stated wish –made by extremist Muslims, among them Osama bin Laden– that Spain return to Islam. Indeed, the Madrid bombers partially justified their actions on the loss of al-Andalus. And during court proceedings in the USA, Zacarias Moussaoui, the French citizen of Moroccan origin and so-called 20th hijacker in the September 11 attacks, prayed to Allah for the return of al-Andalus.
Such statements do not make it easy for Muslims living in Spain while for many Spanish Catholics the return of Islam is an uneasy reminder of historic conflicts. For the latter, al-Andalus is a threat, for the former a dream.
November 2015: A demographic study published in 2014 by the Unión de Comunidades Islámicas de Espana (Union of Muslim Communities of Spain) puts the number of Muslims living in Spain at 1,732,191, roughly 3% of the total population of the country. Of these, 30% were Spanish (native born and converts) and 70% were immigrants, at least 50% of whom were Moroccans. For readers of Spanish, see: http://ucide.org/sites/default/files/revistas/estademograf13.pdf
November 2015: Claims to al-Andalus have more recently been made by ISIS/ISIL** –al-Qaeda’s more violent and extremist rival– as part of an Islamic caliphate stretching from Spain to Indonesia. The dream is undoubtedly real, but the immediate purpose of the claims is more likely directed at recruiting new volunteers with a grandiose vision.
There is a lot of literature on Google on the topic under, for example, ISIS and al-Andalus. See, e.g. http://www.theolivepress.es/spain-news/2014/08/10/isis-spells-out-historic-plan-to-retake-andalucia/
For the meaning of “Daesh,” see http://www.nbcnews.com/storyline/isis-terror/paris-attacks-what-does-daesh-mean-why-does-isis-hate-n463551
Sources.
Carr, Matthew Blood and Faith: The Purging of Muslim Spain New York, London 2009
Collins, Roger Early Medieval Spain: Unity in Diversity 400-1000 London 2nd ed 1995
Constable, Olivia R ed. Medieval Iberia: Readings from Christian, Muslim and Jewish Sources Philadelphia 1997
Fletcher, Richard Moorish Spain London 1992
Watt, Montgomery & Cachia, Pierre A History of Islamic Spain New York 1965
Smith, Colin Christians and Moors in Spain Vol I 711-1150 Warminster, England 1988
Tremlett, Giles Ghosts of Spain: Travel through Spin and its Silent Past New York 2008 (1st edition 2006). Chapter 9 “Moros y Cristianos” (“Moors and Christians”) contains an excellent account of events surrounding the March 11 massacre in Madrid.
Images are from http://commons.wikimedia.org/wiki/Maps_of_Spain