Abu Mansur Nizar (Arabic: أبو منصور نزار, romanized: Abū Manṣūr Nizār; 10 May 955 – 14 October 996), known by his regnal name as al-Aziz Billah (Arabic: العزيز بالله, romanized: al-ʿAzīz biʾllāh, lit. 'the Mighty One through God'), was the fifth caliph of the Fatimid dynasty, from 975 to his death in 996. His reign saw the capture of Damascus and the Fatimid expansion into the Levant, which brought al-Aziz into conflict with the Byzantine emperor Basil II over control of Aleppo. During the course of this expansion, al-Aziz took into his service large numbers of Turkic and Daylamite slave-soldiers, thereby breaking the near-monopoly on Fatimid military power held until then by the Kutama Berbers.
Nizar, the future al-Aziz Billah, was born on 10 May 955, the third son of the fourth Fatimid Caliph, al-Mu'izz li-Din Allah (r. 953–975). His mother, Durzan, usually known as al-Sayyida al-Muʿizzīya ('the Lady of al-Mu'izz') was the chief concubine of al-Mu'izz, and likely of Bedouin origin. She was known for her beautiful singing voice, which earned her the nickname Taghrīd ('Twitter'). She is also recorded as the first Fatimid female patron of architecture. She died in 995.
In 974 his older brother Abdallah ibn al-Mu'izz — who had been the designated heir in preference to the oldest of al-Mu'izz's sons, Tamim — died, and Nizar found himself as his father's designated successor (walī al-ʿahd). The succession was not confirmed in front of the members of the dynasty and court, however, until a day before al-Mu'izz's death on 18 December 975. His official proclamation as caliph was delayed until 9 August 976.
According to the sources, al-Aziz Billah was "tall, with red hair and blue eyes, generous, brave, fond of horses and hunting and very humane and tolerant in disposition". He was marked for his skill as an administrator, reforming the finances of the Fatimid state, standardizing and streamlining the payment of officials, and taking steps to ensure their integrity. At the same time, he was known for his extravagant lifestyle and obsession for precious objects and materials, rare animals and delicacies; it is said that on one occasion, he had carrier pigeons bring him cherries from Ba'albek. The Egyptian economy was also nurtured, and tax revenue thereby increased, through the expansion of streets and canals and the establishment of a stable currency. The general economic well-being was also apparent in an elaborate building programme.
The most influential official during most of his reign was Ya'qub ibn Killis, who was the first in Fatimid history to be designated as 'vizier', in 979. Apart from two brief periods when Ibn Killis fell into disgrace, in 979 and 984, he remained al-Aziz's chief minister until his death in 991. Just like his master, Ibn Killis lived in great luxury, facilitated by a salary of 100,000 gold dinars. Ibn Killis is credited with the capable administration of the public finances, which ensured a full treasury despite the vast sums expended by the luxury-loving Caliph, but also for his role as a patron of men of letters, and the author of a book that codified Fatimid laws. In contrast, his successors did not long remain in office. In the next five years, the post of vizier was occupied by six men: Ali ibn Umar al-Addas, Abu'l-Fadl Ja'far ibn al-Furat, al-Husayn ibn al-Hasan al-Baziyar, Abu Muhammad ibn Ammar, al-Fadl ibn Salih, and Isa ibn Nasturus ibn Surus.
Al-Aziz also undertook major military reforms. Berbers, and especially the Kutama tribe, were traditionally the mainstay of the Fatimid armies, and had played the main role in the takeover of Ifriqiya and the conquest of Egypt and the southern Levant under al-Aziz's predecessors. Until the 970s, the Kutama provided the cavalry, with the infantry composed of Slavic (Ṣaqāliba), Greek (Rūm) and Black African (Sūdān or ʿabīd) slaves.
However, the forays into the Levant revealed the inadequacies of an army based mostly on the Kutama, and from 978, al-Aziz began to introduce mercenaries from the Islamic East, especially Turkic and Daylamite slave-soldiers (ghilmān). The adoption of the ghilmān system had far-reaching repercussions, as the Turkic ghilmān rapidly assumed senior positions in the state and began to rival the Kutama for influence, especially as the flow of new recruits from the Kutama homeland ebbed after c. 987/88. Consequently, a fierce antagonism developed between the two groups, termed Maghāriba ('Westerners') and Mashāriqa ('Easterners') respectively, which would erupt in open warfare after al-Aziz's death.
The employment of the Christian Ibn Nesturus, just as that of the Jew Manashsha as Secretary for Syria, was a prominent example of the Fatimids' tolerance in religious matters, further encouraged under al-Aziz by his Melkite Christian wife. Two of her brothers, Orestes and Arsenius, were appointed as Patriarch of Jerusalem and metropolitan bishop of Cairo, respectively. The Coptic Christians also benefited from the Caliph's favour: for example, in allowing them to rebuild the Saint Mercurius Church despite Muslim opposition, or in refusing to punish a Muslim man who converted to Christianity. This leniency, crowned by the appointment to high office of Ibn Nesturus and Manashsha, was resented by the Muslim populace, incensed by hostile tracts circulating among them. The Caliph was briefly forced to depose his two ministers and imprison them, but soon their undoubted skill ensured their release and reinstatement. Anti-Christian animus was most evident in 996, when merchants from Amalfi were suspected of being responsible for a fire that destroyed the arsenal at Cairo; in a city-wide anti-Christian pogrom, the Amalfitans were murdered and churches were ransacked.
This tolerance did not extend towards the Sunni Muslim population, however, as al-Aziz followed a fervently Isma'ili agenda: he erected inscriptions denouncing the Companions of the Prophet, abolished the Tarawih prayers in 982, and initiated the celebration of the Ashura festival in Cairo. In 991, a man found in possession of the Sunni legal treatise Muwatta Imam Malik was executed.
The reign of Al-Aziz was also culturally significant. Ibn Killis founded the al-Azhar University in Cairo (988) which went on to become the most important centre of learning in the Islamic world. Likewise a library with 200,000 volumes was built in Cairo.
According to Professor Samy S. Swayd, Fatimid missionaries made their Dawah in China during the reign of al-Aziz.
In foreign affairs, al-Aziz concentrated on the extension of Fatimid control over Syria, the conquest of which had begun immediately after the Fatimid conquest of Egypt in 969.
Possession of Syria, and particularly Palestine, was a constant foreign policy objective for many rulers of Egypt both before and after the Fatimids, to foreclose the most likely invasion route into the country by the empires of Western Asia. In the Fatimid case, this drive was given additional impetus by their ambitions to lead the entire Islamic world and unseat the Abbasid Caliphate by conquering Iraq and the eastern Islamic lands, which was possible only via Syria. At the same time, the balance of power in the region was altered with the simultaneous expansion of the Byzantine Empire into northern Syria against the Hamdanid Emirate of Aleppo, culminating in the capture of Antioch in 969. The Fatimids used the Byzantine advance as a major item in their propaganda, claiming to be the only power capable of championing the jihād against the 'infidel' threat. However, Fatimid policy with regard to Syria during the early part of al-Aziz's reign was dominated by the vizier Ibn Killis, who, according to historian Hugh N. Kennedy, "believed that the Fatimids should concentrate on controlling Palestine and southern Syria, while leaving the north of the Hamdanids and their successors to form a buffer state against the Byzantines, with whom the caliph should try to keep on good terms".
Despite initial successes, the first Fatimid invasion of Syria, under the Kutama general Ja'far ibn Fallah, quickly came to a halt through a combination of rebellions by the citizens of Damascus and the Bedouin tribes of the Syrian Desert. In August 971, the Fatimids were defeated in battle against the Bedouin and their Qarmatian allies, leading to the near total collapse of Fatimid control in southern Syria and Palestine, and even a Qarmatian invasion of Egypt in 971 and again in 974.