Throughout his journey from Marrakech to his native Sous, Ibn Tumart found many supporters and followers of his ideas, who quickly assumed active roles in his movement.
As he prepared to declare his revolution, and since he was a scholar and faqih, he believed that claiming to be the true Mahdi (in Islam, the Mahdi is prophesised to be the awaited redeemer of all mankind) could be the best way to fulfil his desired goals. To pave the way for himself, he began spreading the Prophet's hadiths about the awaited Mahdi, and claimed to be of Alawite descent, and that he was descended from the sons of Al-Hassan bin Abi Talib.
Then, during Ramadan 1121, he took the critical step of proclaiming himself "the prophesised infallible Mahdi" heralded by the Prophet's hadiths, among companions and followers. In his book Nazm al-Juman, Moroccan scholar Ibn al-Qattan wrote that, during his speech on that day, Ibn Tumart declared:
"Thanks to Allah, who does what He wants and who judges what He wishes. There is no objection to His command. There is no commentator on His judgment. God praise our master Muhammad who brought good news about the Mahdi who will fill the Earth with equity and justice as it was filled with oppression and injustice. God will send him when the truth is abrogated by falsehood and justice is removed by injustice."
According to Ibn Qattan, the speech continued: "His place is the Far Maghrib, and his time is the last time, and his name is the name of the prophet, who is praised by God and his gracious, intimate angels. The rulers' injustice has appeared and the Earth has been filled with corruption. This is the last time, the name is the name, the lineage is the lineage, and the work is the work."
One can consider the day when Ibn Tumart announced that he was the awaited Mahdi the most decisive day in the history of his movement in particular, and in the history of the Maghreb and the Islamic world in general. From that day, Ibn Tumart was said to have put on the "spiritual dress that he has claimed for his own to support the legitimacy of and holiness his Imamate".
It was not enough for Ibn Tumart to receive an oath of allegiance from the tribes loyal to him; he began to move quickly to prepare his supporters for the expected military confrontation with the Almoravid authority. He then moved to Tinmel, one of the fortified mountain cities, so that he could equip his forces without fearing an attack by the Almoravids.
Meanwhile, he imposed on his followers, who were dubbed the Almohads, a meticulous system of education, which required attending lessons. He also wrote books for the instruction of his men, most prominent among which were Al-Murshada and A'azz Ma Yutlab. He recruited a number of spies among his preachers to ensure he was aware of everything that was going on among his supporters.
Ibn Tumart also fought the tribes of the Berber Masmuda, who initially opposed his call, before eventually joining him. However, throughout his life, he remained suspicious of his disciples and followers. This culminated in a purging of his movement on a massive scale, known as "tamyiz", during which thousands of his supporters whose absolute loyalty was in doubt were executed.
Was Al-Ghazali's prophecy fulfilled?
Following all these preparations, Ibn Tumart clashed with the Almoravid state in numerous successive battles; his armies were able to achieve many impressive victories. Indeed, he almost fulfilled al-Ghazali's prophecy.
But in 1130, before the walls of Marrakech, the capital of the Almoravid dynasty, the Almohad forces were dealt a harsh defeat by the desperate Almoravid fighters, who were fighting for their lives, in the battle known as the Battle of al-Buhayra.
Shortly after that defeat, Mahdi Ibn Tumart died in Tinmel at the age of 50, to be succeeded by his loyal disciple, Abdul-Mu'min ben 'Ali al-Kumi, who transformed the movement into a great empire that included the Maghreb and Andalusia, becoming the first dynasty of what would be known in history as the Almohad Caliphate.
* Translation quoted from The Dearest Quest: A Biography of Ibn Tumart by Wilyam Sharif, 2010, pages 91–92