Appointed by Caliph Abd al-Malik (r. 685–705), Hassan launched a series of campaigns during the closing years of the 7th century, during which he defeated the Byzantines and the Berbers led by al-Kahina.
He was ultimately ousted from his post by the governor of Egypt, Abd al-Aziz ibn Marwan, due to a power struggle for influence over Ifriqiya.
Hassan ibn al-Nu'man hailed from the Ghassanid tribe, which militarily led the Arab tribal confederates of the Byzantine Empire in Syria in the century preceding the Muslim conquest of the region in the 630s.
[1] Hassan was appointed by the Umayyad caliph Abd al-Malik to lead the Arab reconquest of Ifriqiya (modern-day Tunisia) in North Africa.
[1] Abd al-Malik, having consolidated his control over the Caliphate in the Second Muslim Civil War and resumed hostilities with Byzantium in 692,[2] had troops to spare and equipped Hassan with 40,000 men.
[2] Carthage had retained its Byzantine garrison and population through the first Muslim conquest of Ifriqiya in 670, but had long lost its former power and prosperity by the time Hassan entered the city.
[6] Skipping over the Byzantine fortress of Baghaya (al-Majjana),[2] which al-Kahina had preemptively captured and destroyed to prevent its utilization by the Arabs,[6] Hassan met the Berbers at the Battle of Meskiana.
Meanwhile, al-Kahina, according to Ibn Idhari, engaged in a massive scorched earth campaign against the cities and orchards of the Maghreb "from Tripoli to Tangier", leading to a mass flight of the affected areas' inhabitants to the Iberian Peninsula and various Mediterranean islands.
[8] Hassan then turned his attention to Byzantine-held Carthage; upon his approach, the city was abandoned and he ordered its destruction in 698 to prevent future reuse by the Byzantine navy.
[2][8] To that end, he inaugurated a central diwan (government agency) to register and pay the troops and collect the kharaj (poll tax) from local Christians.
[2][8] Hassan is also credited with restoring with stronger building material the Great Mosque of Kairouan, founded by Ifriqiya's first Arab conqueror, Uqba ibn Nafi.