The Battle of Mauropotamos between the armies of the Byzantine Empire and the Abbasid Caliphate, at Mauropotamos (either in northern Bithynia or in Cappadocia). After a failed Byzantine attempt to recover the Emirate of Crete in the previous year, the Abbasids launched a raid into Asia Minor. The Byzantine regent, Theoktistos, headed the army that went to meet the invasion but was heavily defeated, and many of his officers defected to the Arabs. Internal unrest prevented the Abbasids from exploiting their victory, however. A truce and a prisoner exchange were consequently agreed in 845, followed by a six-year cessation of hostilities, as both powers focused their attention elsewhere.