Ottoman sultan (1451–81). He was frustrated while ruling briefly (1444–46) during the retirement of his father, Murad II, but on coming to power backed expansionist factions, and by 1453 had achieved the long-standing Ottoman objective of taking Constantinople and thus uniting the European and Asian parts of the empire. Ceaseless campaigns brought further gains in the Balkans, consolidated control of Asia Minor, and took Otranto in Apulia, but failed to wrest Rhodes from the Knights of St John. He modernized his forces by equipping them with firearms and artillery, and created the institutional framework of the developed Ottoman state.