Constantinople was officially renamed Istanbul on March 28, 1930, as part of Mustafa Kemal Atatürk's sweeping modernization of Turkey. The city had been informally called Istanbul by Turks for centuries — the name likely derives from the Greek phrase 'eis tin polin' (to the city). It had served as the capital of the Roman, Byzantine, and Ottoman empires, arguably the most strategically important city in human history. The renaming was one of many reforms by which Atatürk dismantled the Ottoman sultanate's legacy and built a secular republic.