text: The then Fatimid vizier decided to destroy what he could not control, and broke a deal with the chiefs of these Beduouin tribes.The Fatimids even gave them money to leave.Whole tribes set off with women, children, elders, animals and camping equipment.Some stopped on the way, especially in Cyrenaica, where they are still one of the essential elements of the settlement but most arrived in Ifriqiya by the Gabes region, arriving 1051.The Zirid ruler tried to stop this rising tide, but with each encounter, the last under the walls of Kairouan, his troops were defeated and the Arabs remained masters of the battlefield.The Arabs usually did not take control over the cities, instead looting them and destroying them.The invasion kept going, and in 1057 the Arabs spread on the high plains of Constantine where they encircled the Qalaa of Banu Hammad (capital of the Hammadid Emirate), as they had done in Kairouan a few decades ago.From there they gradually gained the upper Algiers and Oran plains.Some of these territories were forcibly taken back by the Almohads in the second half of the 12th century.The influx of Bedouin tribes was a major factor in the linguistic, cultural Arabization of the Maghreb and in the spread of nomadism in areas where agriculture had previously been dominant.Ibn Khaldun noted that the lands ravaged by Banu Hilal tribes had become completely arid desert.The Almohads originating from modern day Morocco, although founded by a man originating from Algeria known as Abd al-Mu'min would soon take control over the Maghreb.During the time of the Almohad Dynasty Abd al-Mu'min's tribe, the Koumïa, were the main supporters of the throne and the most important body of the empire.