عبد الرحمن الأوسط
In the aftermath of the sack of Amorium, Theophilos sought the aid of other powers against the Abbasid threat: embassies were sent to both the western emperor Louis the Pious (r. 813–840) and to the court of Abd ar-Rahman II (r. 822–852), Emir of Córdoba. The Byzantine envoys were received with honours, but no help materialized. The Abbasids, however, did not follow up on their success. Warfare continued between the two empires with raids and counter-raids for several years, but after a few Byzantine successes a truce and possibly also a prisoner exchange—which excluded the high-ranking captives from Amorium—was agreed in 841. At the time of his death in 842, Mu'tasim was preparing yet another large-scale invasion, but the great fleet he had prepared to assault Constantinople perished in a storm off Cape Chelidonia a few months later. Following Mu'tasim's death, the Caliphate entered a prolonged period of unrest, and the Battle of Mauropotamos in 844 was the last major Abbasid–Byzantine engagement until the 850s.