Question: What Persian general took advantage of Nasr ibn Sayyar being preoccupied with a civil war? 
Sentence (from "Battle of Monte Laturce"): After Monte Laturce, Musa was forced to fully submit to the Emir of Córdoba, who took advantage of Musa's weakness to remove him as "wāli" of the Upper March, initiating a decade-long eclipse of the Banu Qasi.
Relevant evidence: No