Mehmed II brought an end to the Byzantine Empire by capturing Constantinople in 1453 (during the well-known Siege of Constantinople), and other Byzantine cities left in Anatolia and the Balkans. The invasion of Constantinople and successful campaigns against small kingdoms in the Balkans and Turkic territories in Anatolia bestowed immense glory and prestige on the country and the Ottoman State started to be recognized as an empire for the first time.
As can be guessed from his successful campaign against Otranto in southern Italy and his adopting the title Roman Caesar, he was presumably trying to vitalize the Eastern Roman Empire. For a probably similar reason, he gathered Italian humanists and Greek scholars at his court, kept the Byzantine Church functioning, ordered the patriarch to translate the Christian faith into Turkish and called Gentile Bellini from Venice to paint his portrait.
He is also recognized as the first sultan to codify criminal and constitutional law long before Suleyman the Magnificent (also "the Lawmaker") and he thus established the classical image of the autocratic Ottoman sultan (padishah). After the fall of Constantinople, he founded many universities and colleges in the city, some of which are still active.
1451 to 1481