The first full-scale Ottoman Siege of Constantinople took place in 1422 as a result of the Byzantine Emperor Manuel II's attempts to interfere in the succession of Ottoman Sultans, after the death of Mehmed I in 1421. This policy of the Byzantines was often used successfully in weakening their neighbours. The Byzantine defenders won the battle. Contemporary Byzantine tradition ascribed the deliverance of Constantinople to a miraculous intervention by the Theotokos.