structural:summarization
War with the Christian kingdoms of the north

Even before al-Andalus was firmly under his rule, he had restarted the war against King Ordoño II of León, who had taken advantage of the previous troublesome situation to capture some boundary areas and menace the Umayyad territory. In 917 the then emir had sent a large army under his general Ahmad ibn Abi Abda against León, but this force was destroyed at the Battle of San Esteban de Gormaz in September of that year.

Recognizing he had underestimated the power of Ordoño II, in 920 Abd al-Rahman mustered another powerful army to reclaim the territories lost after the previous campaign. He captured the forts of Osma and San Esteban de Gormaz. After defeating King Sancho Garcés I of Navarre and the king of León at Valdejunquera on 26 July, he penetrated into Navarre, overcoming Aragon by the classic route of the invasions from the south. Abd al-Rahman reached the Basque city of Pamplona, which was sacked and its cathedral church demolished.

In 924 Abd al-Rahman felt obliged to avenge the massacre of Viguera castle perpetrated by King Sancho Ordóñez of Navarre one year earlier. He launched a counter offensive against Sancho in which Abd al-Rahman devastated a large area of Basque territory.

The succession crisis which struck León after Ordoño II's death in the same year caused hostilities to cease until Ramiro II gained the throne in 932; a first attempt by him to assist the besieged rebels in Toledo was repelled in 932, despite the Christian king capturing Madrid.

In 934, after reasserting supremacy over Pamplona and Álava, Abd al-Rahman forced Ramiro to retreat to Burgos, and forced the Navarrese queen Toda, his aunt, to submit to him as a vassal and withdraw from direct rule as regent for her son García Sánchez I. In 937 Abd al-Rahman conquered some thirty castles in León. Next he turned to Muhammad ibn Hashim al-Tugib, governor of Zaragoza, who had allied with Ramiro but was pardoned after the capture of his city.

Despite early defeats, Ramiro and García were able to crush the caliphal army in 939 at the Battle of Simancas, and almost kill Abd al-Rahman, due to treason by Arab elements in the caliph's army. After this defeat, Abd al-Rahman stopped taking personal command of his military campaigns. His cause was helped, however, by Fernán González of Castile, one of the Christian leaders at Simancas, who subsequently launched a sustained rebellion against Ramiro. The victory of Simancas enabled the Christian kingdom to maintain the military initiative in the peninsula until the defeat of Ramiro's successor, Ordoño III of León, in 956. However, they did not press this advantage as civil war broke out in the Christian territories.

In 950 Abd al-Rahman received in Córdoba an embassy from count Borrell II of Barcelona, by which the northern county recognized caliphal supremacy in exchange for peace and mutual support. In 958, Sancho, the exiled king of León, King García Sánchez of Pamplona, and his mother Queen Toda all paid homage to Abd al-Rahman in Córdoba.

Until 961, the caliphate played an active role in the dynastic strife characterising the Christian kingdoms during the period. Ordoño III's half-brother and successor, Sancho the Fat, had been deposed by his cousin Ordoño IV. Together with his grandmother Toda of Pamplona, Sancho sought an alliance with Córdoba. In exchange for some castles, Abd al-Rahman helped them to take back Zamora (959) and Oviedo (960) and to overthrow Ordoño IV.