After the conquest of Constantinople in 1453, the sultans of the Ottoman Empire laid claim to be the legitimate Roman emperors, in succession to the Byzantine emperors who had previously ruled from Constantinople. Based on the concept of right of conquest, the sultans at times assumed the styles kayser-i Rûm ("Caesar of Rome", one of the titles applied to the Byzantine emperors in earlier Ottoman writings) and basileus (the ruling title of the Byzantine emperors). The assumption of the heritage of the Roman Empire also led the Ottoman sultans to claim to be universal monarchs, the rightful rulers of the entire world.