On Friday, a Turkish court opened the way for Hagia Sophia to be restored as a mosque, threatening to set in motion an international furor around a World Heritage Site cherished by both Christians and Muslims for its religious significance, stunning structure, and symbol of conquest.
Hagia Sophia was originally built as a cathedral in the sixth century and stands as the world’s greatest example of Byzantine Christian architecture. Yet it has been a source of Christian-Muslim conflict throughout its long history, having been at the forefront of Christendom for almost a century, and then of the Muslim Ottoman Empire since its conquest.
It has been a museum for the last 80 years, open to all, a monument of relative peace and a symbol to secularism which was part of the foundation of the modern Turkish state.
The court’s decision announced Friday revokes the museum status and will require Hagia Sophia to once again become a functioning mosque. It was a long-sought-after decision by conservative Muslims in Turkey and beyond, and especially by President Recep Tayyip Erdogan, whose popularity wanes after 18 years atop Turkish politics.
Opponents say his push to make the change aims to stir his nationalist and religious base by glorifying Ottoman history and stepping back from Turkey’s almost centuries-long devotion to secularism.
How the ruling changed life around the monument was not immediately clear. Cevdet Yilmaz, the spokesman for the Justice and Development Party of Mr. Erdogan, known as the A.K.P., said the government would determine how the change will be carried out.
Mr. Erdogan is expected to make the final decision and can choose to pray only on formal occasions, as he did in May to mark the anniversary of the city’s Ottoman conquest. Yet its followers could be demand freedom for regular prayers to enter the building.