Under this dynasty the Moorish empire was extended over present-day Morocco, Western Sahara, Mauritania, Gibraltar, Tlemcen (in Algeria) and a great part of what is now Senegal and Mali in the south, and Spain and Portugal to the north in Europe. At its extent, the empire stretched 3,000 kilometres north to south (an all-time latitude spanner until Spanish America).
“Almoravids” is a transcription of “Al-Murabitun”. The exact meaning of "Murabit" is a matter of controversy. Some have suggested that the word might be derived from the Arabic ribat meaning fortress (a term with which it shares the root r-b-t). Most historians, however, now believe that it refers to ribat meaning "ready for battle" (cf. jihad).
His preaching was before-long rejected by the Lamtunas; so on the advice of Yahya, who accompanied him, he retired to Saharan regions from which his influence spread. There was no element of heresy in his creed, which was mainly distinguished by a strict obedience to the Qur'an, and the orthodox tradition or Sunnah.
From the year 1053, the Almoravids began to spread their religious way to the Berber areas of the Sahara, and to the regions south of the desert. They converted Takrur (a small state in modern Senegal) to Islam, and after winning over the Sanhaja Berber tribe, they quickly took control of the entire desert trade route, seizing Sijilmasa at the northern end in 1054, and Aoudaghost at the southern end in 1055. Yahya ibn Ibrahim was killed in a battle in 1056, but Abd-Allah ibn Yasin, whose influence as a religious teacher was paramount; named his brother Abu-Bakr Ibn-Umar as chief. Under him, the Almoravids soon began to spread their power beyond the desert, and subjected the tribes of the Atlas Mountains. They then came in contact with the Berghouata, a branch of the Zenata of central Morocco, who followed a "heresy" founded by Salih ibn Tarif, three centuries earlier. The Berghouata made a fierce resistance, and it was in battle with them that Abdullah ibn Yasin was killed. They were, however, completely conquered by Abu-Bakr Ibn-Umar, who took the defeated chief's widow, Zainab, as a wife.
In 1061, Abu-Bakr Ibn-Umar made a division of the power he had established, handing over the more-settled parts to his cousin Yusuf ibn Tashfin, as viceroy; resigning to him also his favourite wife Zainab. For himself, he reserved the task of suppressing the revolts which had broken out in the desert, but when he returned to resume control, he found his cousin too powerful to be superseded. He returned to the Sahara, where, in 1087, having been wounded with a poisoned arrow, he died.
Yusuf ibn Tashfin had in the meantime brought what is now known as Morocco, Western Sahara and Mauretania into complete subjection; and in 1062, had founded the city of Marrakech. In 1080, he conquered the kingdom of Tlemcen (in modern-day Algeria) and founded the present city of that name, his rule extending as far east as Oran.
In 1086 Yusuf ibn Tashfin was invited by the Muslim princes in the Iberian Peninsula (Al-Andalus) to defend them against Alfonso VI, King of Castile and León. In that year, Yusuf ibn Tashfin crossed the straits to Algeciras, inflicted a severe defeat on the Christians at the az-Zallaqah. He was prevented from following up his victory by trouble in Africa, which he had to settle in person.
When he returned to Iberia in 1090, it was avowedly for the purpose of deposing the Muslim princes, and annexing their states. He had in his favour the mass of the inhabitants, who had been worn out by the oppressive taxation imposed by their spend-thrift rulers. Their religious teachers, as well as others in the east, (most notably, al-Ghazali in Persia and al-Tartushi in Egypt, who was himself an Iberian by birth, from Tortosa), detested the native Muslim princes for their religious indifference, and gave Yusuf a fatwa -- or legal opinion -- to the effect that he had good moral and religious right, to dethrone the rulers, whom he saw as heterodox and who did not scruple to seek help from the Christians, whose habits he claimed they had adopted. By 1094, he had removed them all, except for the one at Zaragoza; and though he regained little from the Christians except Valencia, he re-united the Muslim power, and gave a check to the reconquest of the country by the Christians.
The Almoravid power was at its height at Yusuf's death, and the Moorish empire then included all North-West Africa as far as Algiers, and all of Iberia south of the Tagus, with the east coast as far as the mouth of the Ebro, and included the Balearic Islands.
Ali ibn Yusuf was a pious non-entity, who fasted and prayed while his empire fell to pieces under the combined action of his Christian foes in Iberia and the agitation of Almohads (the Muwahhids) in Morocco. After Ali ibn Yusuf's death in 1142, his son Tashfin ibn Ali lost ground rapidly before the Almohads, and in 1146 he was killed by a fall from a precipice, while endeavouring to escape after a defeat near Oran.
His two successors were Ibrahim ibn Tashfin and Is'haq ibn Ali, but their reign was only short. The conquest of the city of Marrakech by the Almohads in 1147 marked the fall of the dynasty, though fragments of the Almoravids (the Banu Ghaniya), continued to struggle in the Balearic Islands, and finally in Tunisia.
Interestingly, family names such as Morabito, Murabito and Mirabito are common in western Sicily, the Aeolian Islands and southern Calabria in Italy. These names may have appeared in this region as early as the 11th century, when Robert Guiscard and the Normans defeated the Saracens (Muslims) in Sicily. In addition to southern Italy, there are also sizable populations of Mourabit (also spelled Morabit or Murabit) in modern-day Morocco, Tunisia and Mauritania.