The reconversion of Hagia Sophia, a symbol of Istanbul and a marvel of Byzantine art, into a mosque is a historic moment. The controversial move, put in motion by President Recep Tayyip Erdogan's decree, could fairly be seen as the Turkish Reconquista.

Istanbul was Constantinopole in 1453 when it was conquered by the Muslim-Turkish Ottomans under Mehmed II, and the East Roman (Byzantine) Empire ceased to exist. Some 40 years later, Catholic monarchs Isabella I of Castile and Ferdinand II of Aragon conquered Granada, ending the only Muslim kingdom in Europe in what became known as the "Reconquista." 

The first thing Mehmed II did after entering Istanbul was to visit Hagia Sophia, the Greek Christian Orthodox cathedral. The Ottoman sultan swiftly converted it into a mosque. Constructed in 537 by the Roman Emperor Justinianus, Hagia Sophia was the world’s largest cathedral for almost a thousand years. For pious Muslim Turks, it signified the glory of the Ottoman Empire, a place of worship converted into a mosque by Mehmed, who they venerated almost as a saint.

The conquest of Istanbul, transforming the Ottoman state into an empire, bears great significance for Turkish nationalists and conservatives.