Abdallah al-Mahdi Billah
Abu Muhammad Abdallah ibn al-Husayn, better known by his regnal name Abu Muhammad Abdallah al-Mahdi Billah, was the founder of the Isma'ili Fatimid Caliphate, the only major Shi'a caliphate in Islamic history, and the eleventh imam of the Isma'ili faith.
Background
Shi'ism in the late 9th century
Ever since the murder of Ali, the son-in-law of Muhammad, in 661, which led to the establishment of the Umayyad Caliphate, a large part of the Muslim community rejected the Umayyads as usurpers and called for the establishment of a regime led by a member of the Ahl al-Bayt, the Family of Muhammad. The Abbasids, who claimed descent from Muhammad's paternal uncle Abbas ibn Abd al-Muttalib, profited from this during their rise to power against the Umayyads; but their claim too was rejected by the Shi'a, who insisted on the exclusive right of the descendants of al-Husayn and Hasan, Ali's sons by Muhammad's daughter Fatimah. A line of imams emerged from the offspring of Husayn, who did not openly lay claim to the caliphate, but were considered by their followers as the true representatives of God on earth.The sixth imam, Ja'far al-Sadiq, had appointed his son Isma'il ibn Ja'far as his successor, but Isma'il died before his father, and when al-Sadiq himself died in 765, the succession was left open. One faction of Shi'a held that al-Sadiq had designated another son, Musa al-Kazim, as his heir. Others followed other sons, Muhammad and Abdallah al-Aftah—shortly after his death, they went over to Musa's camp—or even refused to believe that al-Sadiq had died, and expected his return as a messiah. Musa's adherents, who constituted the majority of al-Sadiq's followers, followed his line down to the twelfth imam, Muhammad al-Mahdi, who vanished in 874. Another branch believed that Ja'far was followed by a seventh imam, who also had gone into hiding; hence this party is known as the Seveners. The exact identity of that seventh imam was disputed, but by the late 9th century had commonly been identified with Muhammad, son of Isma'il and grandson of al-Sadiq. From Muhammad's father, Isma'il, the sect receives its name of "Isma'ili". Neither Isma'il's nor Muhammad's lives are well known, and after Muhammad's death during the reign of Harun al-Rashid, the history of the early Isma'ili movement becomes obscure.
Both the Twelvers and the Seveners held that their final imams were not dead, but had simply gone into hiding, and that they would soon return as a messiah, a mahdī or qāʾīm, to usher in the end times. The mahdī would rapidly overthrow the usurping Abbasids and destroy their capital Baghdad, restore the unity of the Muslims, conquer Constantinople, ensure the final triumph of Islam and establish a reign of peace and justice. The Isma'ilis in particular believed that the mahdī would reveal the true, "inner" meaning of religion, which was until then reserved for a few selected initiates. The mahdī would dissolve the outer forms and strictures of Islam, since henceforth the true religion, the religion of Adam, would be manifested without the need for symbols and other mediating devices.
Secret leadership of the Isma'ili ''daʿwa'' at Salamiya
While the mahdī Muhammad ibn Isma'il remained hidden, however, he would need to be represented by agents, who would gather the faithful, spread the word, and prepare his return. The head of this secret network was the living proof of the imam's existence, or "seal". The first known ḥujja was a certain Abdallah al-Akbar, a wealthy merchant from Askar Mukram, in what is now southwestern Iran. Apart from improbable stories circulated by later anti-Isma'ili polemicists, his exact origin is unknown. His teachings led to his being forced to flee his native city to escape persecution by the Abbasid authorities, and seek refuge in Basra, where he claimed to belong to the Aqil branch of the Banu Hashim, the clan of Muhammad. Once again, his teachings attracted the attention of the authorities and he moved on to the small town of Salamiya on the western edge of the Syrian Desert. There he settled as a merchant from Basra, and had two sons, Ahmad and Ibrahim. When Abdallah died, Ahmad succeeded his father as the head of the Isma'ili movement, and was in turn succeeded by his younger son, Muhammad, known as Abu'l-Shalaghlagh.During the late 9th century, millenialist expectations increased in the Muslim world, coinciding with a deep crisis of the Abbasid Caliphate during the decade-long Anarchy at Samarra, the rise of breakaway and autonomous regimes in the provinces, and the large-scale Zanj Rebellion, whose leader claimed Alid descent and proclaimed himself as the mahdī. In this chaotic atmosphere, where the Abbasids were preoccupied with suppressing the uprising, the Isma'ili daʿwa spread rapidly, aided by dissatisfaction among Twelver adherents with the political quietism of their leadership and the recent disappearance of the twelfth imam. Missionaries like Hamdan Qarmat and his brother-in-law Abu Muhammad Abdan spread the network of agents to the area round Kufa in the late 870s, and from there to Yemen and thence India, Bahrayn, Persia, and the Maghreb. The real leadership remained hidden at Salamiya, and only the chief dā'īs of each region, such as Hamdan Qarmat, knew and corresponded with it. The true head of the movement remained hidden even from the senior missionaries, however, and a certain Fayruz functioned as chief missionary and "gateway" to the hidden leader.
Early life
The future caliph al-Mahdi Billah was born as Sa'id, the son of Ahmad's elder son, al-Husayn, who died around 880. The official biography gives the date of birth as 31 July 874, although a different tradition gives a date exactly one year earlier. After his father's death, he was fostered by his uncle Abu'l-Shalaghlagh, who was without an heir of his own—his son and grandchild were reportedly captured and imprisoned by the Abbasids. Sa'id was thus designated as his successor, and given his uncle's daughter in marriage. Most of the information about Sa'id's early life comes from the memoirs of the eunuch chamberlain Ja'far, who was a few months older than Sa'id and came with him to the household at Salamiya. The two were reared by the same wet-nurse, and Ja'far became a close confidant of Sa'id until his death.Sa'id's only child, Abd al-Rahman, the future al-Qa'im bi-Amr Allah, was born in March or April 893. While ostensibly merely the stewards for the absent imam, Ja'far reports that Abu'l-Shalaghlagh—perhaps encouraged by the rapid progress of the daʿwa, now establishing armed strongholds—secretly declared himself to senior members of the daʿwa not as the ḥujja for Muhammad ibn Isma'il, but the actual imam; and that he claimed for his nephew the title of mahdī, and the latter's infant son the title of qāʾīm. Various genealogies were later put forth by the Fatimids to justify this claim. In the most common, Abdallah the Elder was proclaimed to be the son of Muhammad ibn Isma'il, but even in pro-Isma'ili sources, the succession and names of imams who supposedly preceded Ahmad is not the same; for example, Sa'id himself in a letter claimed descent not from Muhammad ibn Isma'il, but from the latter's older brother Abdallah. Anti-Isma'ili Sunni and Twelver sources of course reject any Fatimid descent from the Alids altogether and consider them impostors. The situation is further complicated by the use of the title qāʾīm, normally a synonym for the mahdī, for Sa'id's son. This has led to suggestions of two parallel lines of imams, one public, serving as trustees of the hidden, real one. In this interpretation, Sa'id was the last representative of the former line, and his "son" was the genuine imam.
Leadership of the ''daʿwa''
When Abu'l-Shalaghlagh died around 899, Sa'id became the new head of the movement. Soon after, the letters from Salamiya revealed changes in the official doctrine of the daʿwa. This worried Hamdan Qarmat, who sent his brother-in-law to Salamiya to investigate the matter. It was there that Abdan learned that Sa'id claimed that the imam was not Muhammad ibn Isma'il, but Sa'id's father al-Husayn, and now Sa'id himself. This caused a major rift in the movement: Hamdan denounced the leadership in Salamiya, gathered the Iraqi dā'īs and ordered them to cease the missionary effort. Shortly after he disappeared from his headquarters.It was Al-Shi'i's success which was the signal to Al Mahdi to set off from Salamyah disguised as a merchant. In 905 he started proselytising. However, he was captured by the Aghlabid ruler Ziyadat-Allah due to his Ismaili beliefs and thrown into a dungeon in Sijilmasa. In early 909 Al-Shi'i sent a large expedition force to rescue Al Mahdi, conquering the Khariji state of Tahert on its way there. After gaining his freedom, Al Mahdi became the leader of the growing state and assumed the position of imam and caliph. Al Mahdi then led the Kutama Berbers who captured the cities of Qairawan and Raqqada. By March 909, the Aghlabid Dynasty had been overthrown and replaced with the Fatimids. As a result, the last stronghold of Sunni Islam in North Africa was removed from the region.
Reign
Al-Mahdi established himself at the former Aghlabid residence at Raqqada, Al-Qayrawan. After that his power grew. At the time of his death he had extended his reign over the Maghreb, but campaigns into Egypt faltered against the resistance of the Abbasids, with heavy casualties.Al-Mahdi founded the capital of his empire, Al-Mahdiyyah, on the Tunisian coast sixteen miles south-east of Al-Qayrawan, which he named after himself. The city was located on a peninsula on an artificial platform "reclaimed from the sea", as mentioned by the Andalusian geographer Al-Bakri. The Great mosque of Mahdia was built in 916 on the southern side of the peninsula.
Al-Mahdi took up residence there in 920.
In 922 the Bulgarian emperor Simeon I sent envoys to al-Mahdi to propose a joint attack on the Byzantine capital Constantinople with the Bulgarians providing a large land army, and the Arabs a navy. It was proposed that all spoils would be divided equally, with the Bulgarians keeping Constantinople and the Fatimids gaining the Byzantine territories in Sicily and South Italy. As a result of the Byzantine–Bulgarian war of 913–927, by 922 the Bulgarians controlled almost the whole Balkan peninsula but Simeon I's main objective to capture Constantinople remained out of his reach because he lacked a navy. Although the Byzantines and the Fatimids had concluded a peace treaty in 914, since 918 the Fatimids had renewed their attacks on the Italian coast.
Al-Mahdi accepted the proposal and sent back his own emissaries to conclude the agreement. On the way home the ship was captured by the Byzantines near the Calabrian coast and the envoys of both countries were sent to Constantinople. When the Byzantine emperor Romanos I learned about the secret negotiations, the Bulgarians were imprisoned, while the Arab envoys were allowed to return to Al-Mahdiyyah with rich gifts for the caliph. The Byzantines then sent their own embassy to North Africa to outbid Simeon I and eventually the Fatimids agreed not to aid Bulgaria.
After his death, Al-Mahdi was succeeded by his son, Abu Al-Qasim Muhammad Al-Qaim, who continued his expansionist policy.