عبد الرحمن الأوسط
While Musa had been orphaned at an early age, his military activity may have begun in the 820s, and the Banu Qasi (possibly Musa himself) most probably participated in the second battle of the pass of Roncevaux along with their relatives of Pamplona, an event leading to the establishment of the kingdom of Pamplona. Historians agree that in the 840s, after the expulsion from his lands of a kinsman, 'Abd al-Jabbar ibn Qasi, Musa launched a series of revolts in conjunction with his maternal half-brother, Íñigo Arista of Pamplona. Abd ar-Rahman II defeated them, and took Musa's son Lubb hostage. Musa repeatedly submitted, only to rise again. After repeated rebellions he controlled a region along the Ebro from Borja to Logroño, including Tudela, Tarazona, Arnedo and Calahorra. The 851/2 deaths of Íñigo Arista and Abd ar-Rahman II, as well as a victory over Christian forces at Albelda, gave Musa unprecedented status. The new emir, Muhammad I of Córdoba named Musa the Wali of Zaragoza and governor of the Upper March. Over the next decade Musa expanded the family's lands to include Zaragoza, Najera, Viguera and Calatayud, while also governing Tudela, Huesca and Toledo, and according to the "Chronica Adefonsi tertii regis", Musa had his followers call him "the third king of "Spaniae"".