Can Christianity survive, in the face of persecution and conflict, in the region of its birth? The BBC's Jane Corbin travelled across the Middle East - through Iraq and Syria - to investigate the plight of Christians, as hundreds of thousands flee Islamic militancy in the region.
As I climbed the steep mountain path above the plain of Nineveh, Iraq, the sound of monks chanting and the smell of incense drifted out of the 4th Century monastery of St Matthew. Once, 7,000 monks worshipped here when Christianity was the official religion of the Roman empire.
Almost the whole population was Christian then. Their numbers have dwindled and now there are only six monks - and no pilgrims dare to visit. "We are on the frontline with Isis and people are afraid to come here," Father Yusuf told me. "We are worried about everything: our people, our family, Christianity."
Kurdish fighters guard the monastery and on the plain I heard artillery fire and saw plumes of smoke from Western airstrikes on the positions of IS, the so-called Islamic State. They swept across the plain of Nineveh last year, forcing tens of thousands of Christians to flee from Mosul, Iraq's second city, and surrounding towns and villages.