The Almohads, who ruled the Islamic west and al-Andalus during the sixth/twelfth century and the first half of the seventh/thirteenth century, based their legitimacy as caliphs on the fact that the founder of the Almohad dynasty, 'Abd al-Mu'min, had been the favourite pupil and political successor of the mahdi Ibn Tuman. Research on Ibn Tumart and the Almohads has always to take into account that what the sources tell about them has suffered both the evolution of the Almohad movement itself and the 'de-almohadizatio' that took place after the failure of Almohadism. For some time the Almohad caliphs tried to develop the implications that Ibn Tumart's mandism had for their own role in the Muslim community. The most striking aspect of the Almohad caliphate is its explicit attempt at signalling its discontinuity with the recent past.