The most prominent member of the Hamdanid dynasty, Sayf al-Dawla originally served under his elder brother in the latter's attempts to establish his control over the weak Abbasid government in Baghdad during the early 940s CE. After the failure of these endeavours, the ambitious Sayf al-Dawla turned towards Syria, where he confronted the ambitions of the Ikhshidids of Egypt to control the province. After two wars with them, his authority over northern Syria, centred at Aleppo, and the western Jazira, centred at Mayyafariqin, was recognized by the Ikhshidids and the Caliph. A series of tribal rebellions plagued his realm until 955, but he was successful in overcoming them and maintaining the allegiance of the most important Arab tribes. Sayf al-Dawla's court at Aleppo became the centre of a vibrant cultural life, and the literary cycle he gathered around him, including the great al-Mutanabbi, helped ensure his fame for posterity.
Sayf al-Dawla was widely celebrated for his role in the Arab–Byzantine Wars, facing a resurgent Byzantine Empire that in the early 10th century had begun to reconquer Muslim territories. In this struggle against a much superior enemy, he launched raids deep into Byzantine territory and managed to score a few successes, and generally held the upper hand until 955. After that, the new Byzantine commander, Nikephoros Phokas, and his lieutenants spearheaded an offensive that broke Hamdanid power. The Byzantines annexed Cilicia, and even occupied Aleppo itself briefly in 962. Sayf al-Dawla's final years were marked by military defeats, his own growing disability as a result of disease, and a decline in his authority that led to revolts by some of his closest lieutenants. He died in early 967, leaving a much weakened realm, which by 969 had lost Antioch and the Syrian littoral to the Byzantines and become a Byzantine tributary.
Sayf al-Dawla was born Ali ibn Abdallah, the second son of Abdallah Abu'l-Hayja ibn Hamdan (died 929), son of Hamdan ibn Hamdun ibn al-Harith, who gave his name to the Hamdanid dynasty. The Hamdanids were a branch of the Banu Taghlib, an Arab tribe resident in the area of the Jazira (Upper Mesopotamia) since pre-Islamic times. The Taghlibs had traditionally controlled Mosul and its region until the late 9th century, when the Abbasid government tried to impose firmer control over the province. Hamdan ibn Hamdun was one of the most determined Taghlibi leaders in opposing this move. Notably, in his effort to fend off the Abbasids, he secured the alliance of the Kurds living in the mountains north of Mosul, a fact which would be of considerable importance in his family's later fortunes. Family members intermarried with Kurds, who were also prominent in the Hamdanid military.
Hamdan was defeated in 895 and imprisoned with his relatives, but his son Husayn ibn Hamdan managed to secure the family's future. He raised troops for the Caliph among the Taghlib in exchange for tax remissions, and established a commanding influence in the Jazira by acting as a mediator between the Abbasid authorities and the Arab and Kurdish population. It was this strong local base which allowed the family to survive its often strained relationship with the central Abbasid government in Baghdad during the early 10th century. Husayn was a successful general, distinguishing himself against the Kharijites and the Tulunids, but was disgraced after supporting the failed usurpation of Ibn al-Mu'tazz in 908. His younger brother Ibrahim was governor of Diyar Rabi'a (the province around Nasibin) in 919 and after his death in the next year he was succeeded by another brother, Dawud. Sayf al-Dawla's father Abdallah served as emir (governor) of Mosul in 905/6–913/4, was repeatedly disgraced and rehabilitated, until re-assuming control of Mosul in 925/6. Enjoying firm relations with the powerful Mu'nis al-Muzaffar, he later played a leading role in the short-lived usurpation of al-Qahir against al-Muqtadir in 929, and was killed during its suppression.
Despite the coup's failure and his death, Abdallah had been able to consolidate his control over Mosul, becoming the virtual founder of a Hamdanid-ruled emirate there. During his long absences in Baghdad in his final years, Abdallah relegated authority over Mosul to his eldest son, al-Hasan, the future Nasir al-Dawla. After Abdallah's death, Hasan's position in Mosul was challenged by his uncles, and it was not until 935 that he was able to secure confirmation by Baghdad of his control over Mosul and the entire Jazira up to the Byzantine frontier.