Britannica, Istanbul:When the Republic of Turkey was founded in 1923, the capital was moved to Ankara, and Constantinople was officially renamed Istanbul in 1930.
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"Osman I". Encyclopedia Britannica. Osman I, also called Osman Gazi, (born c. 1258—died 1324 or 1326), ruler of a Turkmen principality in northwestern Anatolia who is regarded as the founder of the Ottoman Turkish state.