Imam al-Mansur (AS) was born in 302 H. in Kairwan, the first Fatemi Imam to be born in Maghrib. His name was Ismail and kun'yat was Abu Tahir, Laqab al-Mansur bi-Amrillah (Victorious by the command of God). His entire upbringing was in North Africa, amid an atmosphere of battle and revolts, which helped him to develop a military spirit and discipline. He acceded the throne of Imamat on 334H at the age of 32.
Abu Yazid Dajjal (LA), traced his tribal origin to the clan of Ifran, one of the leading branches of the Zanata, who were at rivalry with the Kutama tribe, which was loyal to the Fatimeen. Abu Yazid (LA) was a schoolmaster at Taharat, and had a leaning towards the doctrines of the Kharijis. After spending sometime in Taharat, he returned to Qastilia, where he started his anti-Fatemi agitation in 316 and soon procured a large following. With the Berbers moving quickly to his side, Abu Yazid (LA) engineered his revolt against the Fatemeen in 332 H. During Imam al-Qaim's time, Abu Yazid (LA) conquered many important towns, including Baja, Raqqada and Kairwan. Imam al-Qaim (AS) sought refuge in Mahdiya, at which Abu Yazid laid a siege in 334 A.H. Due to the high morale which the Imam (AS) inspired and due to the large reserves of food, which were wisely stocked in the town in advance, the Fatemi capital was able to outlive the siege and tireout the besiegers, who under Abu Yazid (LA), withdrew to Susa. It is then that Imam al-Mansur accended the throne of Imamat. The death of Imam Qaim (AS) was kept a secret from everyone including family members till the year 335 H, when on the day of Idd al-Fitr it was declared on the pulpits of Mahdiya by the orders of Imam al-Mansur (AS).
The first task of Imam al-Mansur (AS) was to relieve Susa. Soon he started an enormous campaign against Adu Yazid (LA). While the Imam (AS) was engaged in Jihad, the administration of Mahdiya and other parts of the empire was entrusted to Ustaz Juzar (RA), the servent of Amirul Mumineen al-Mansur (AS). Imam al-Mansur (AS) himself, commanded the forces and inflicted a severe defeat on Abu Yazid (LA), and drove him back to Kairwan, then he went to Sabta. The Imam (AS) reached Kairwan and helped the suffered people. He (AS) was warmly received in Kairwan, and he also personally conducted a close chase, defeating Abu Yazid near Tubna and then around Masila. On Saturday 23 Moharram 336 H, Imam al-Mansur, inflicted a final defeat on the Khariji Berbers in the mountains of Kiyana, where the rebels had entrenched themselves in a fortress, called Qalat Bani Hammad.
Abu Yazid (LA) was suppressed and taken prisoner, but was died of his wounds. Syedna Jafar bin Mansur al-Yemen is the contemporary authority, who had also composed few poems about the revolt of Abu Yazid Dajjal (LA) and the marvellous actions of al-Mansur (AS).
When Imam al-Mansur was subduing Abu Yazid's revolt, a report reached to him about a petty uprising of Hamid bin Nasl, the chief of the Maghrib, who had laid a siege over Tahrat soon after announcing his loyalty with the Umayyads of Spain. After crushing the revolt of Abu Yazid (LA), Imam al-Mansur (AS) focused his attention at the new rising, and himself commanded his army. He inflicted a defeat to Hamid and appointed Masrur al-Khadim the governor of Tahrat.
Imam al-Mansur (AS) was unable to pay attention towards Sicily during the revolt of Abu Yazid (LA), where Ibn Ataf was an inefficient governor. Taking advantage of his weakness, the Byzantines stopped the payment of the tribute to the Fatimeen. In the meantime, the inhabitants of Sicily also rose against Ibn Ataf, who hid himself in the old castle of Palermo. Confronted by the chaotic situation caused by the rebellious at Palermo and Agrigento in Sicily against the Fatimi amirs, Imam al-Mansur (AS) entrusted Sicily's administration to those whose fidelity was proven beyond doubt, and who, moreover, could maintain a neutral stand, therefore, the Imam (AS) appointed Hasan bin Ali al-Kalbi as the governor of Sicily in 336 H.
In Sicily, Hasan bin Ali al-Kalbi finished the internal uprisings and restored peace. He also solidified his army, forcing the Byzantine emperor to resume the payment of the tribute to the Fatemi. It should be remembered that the Byzantine had never paid tribute to any rulers before the Fatimeen. Byzantine, which was supposed to be one of the most powerful empires was subdued by the Fatemeen (AS).
In 340 H, Imam al-Mansur was reported that the emperor of Rome was about to invade the Fatimid territories, thus a naval forces was dispatched under Faraj Saqali. Hasan bin Ali al-Kalbi, the governor of Sicly and Faraj jointly invaded Kaloria and defeated the French forces. The Roman emperor was obliged to send tributes and a peace-negotiating embassy to the Fatimid court.
In 335 H, Imam al-Mansur (AS) had ordered yet another new capital built a short distance southwest of Kairwan, called Mansuria. It served a new Fatemi capital after Mahdiya. In later years Syedna Qadi Noman (RA) was appointed the Chief Justice of the Mansuria and the Fatemi empire by Imam al-Mansur (AS).
After seven years of rule, Imam al-Mansur passed away in 341 A.H., at the age of 39.
Refernce: Uyyun al-Akhbar -5
Note: Aqa Moula Syedna Mohammad Burhannudin (TUS) is the first Dai-al-Mutlaq to tour Maghrib (North Africa), where he is said to have indicated the exact location where La'een Abu Yazid Dajjal was captured by Imam al-Mansur (AS).