Apart from praying and lamenting, what can concerned outsiders, such as the Western churches, do to help Christians in northern Iraq? That is a real question, not least because Iraqi Christian leaders are in a quandary themselves.
Until a few weeks ago, Mosul and its environs remained a bastion, however depleted, of ancient Christian communities whose collective memory goes back to the faith's earliest years. To understand the varieties of Iraqi Christian, you have to study theology.
Some have roots in Nestorianism, which stressed the difference between the divine and human natures of Jesus Christ. Some have their origins in the Miaphysite doctrine, holding that Christ had only one, divine nature.
Within both categories, some have reconciled with the Church of Rome, others haven't. Some (like most mainstream Christian churches) hew to the teaching laid down in 451 that Christ had both a divine nature and a human one but was a single person.
All this helps to explain why a single Iraqi town can have several Christian bishops, each with his own sonorous titles. Chaldean Catholics (Christians with Nestorian roots who have been reconciled with Rome for 500 years) are the biggest group.
Exact figures about Iraqi Christianity are hard to come by. It is often asserted that about 400,000 to 500,000 Christians live in the country, down from a total before the 2003 war of perhaps 1.5 million. Other observers think as few as 200,000 may be left. The majority of the remaining Christians live in the far north of the country. Last month, when the extremist Sunni fighters of ISIS over-ran Mosul, thousands of Christians joined other townspeople in fleeing; many Christians headed for an immediately adjacent area, known as Nineveh Plains.
That district had long been a stronghold of Christians as well as lesser known religious groups such as Yazidis and Mandeans. If Nineveh Plains seemed marginally safer, that was only because Christians and others were being protected by the Kurds, who have responded to the Sunni advance by expanding the area under their control. Since then, ISIS and the Kurds have been battling over the Plains; some Christians have moved even deeper into Kurdish-controlled territory.
All this highlights the dilemmas facing the Iraqi Christians. Should they try to secure their future by massing in a 'safe area' and seeking to maximise the autonomy of that area?
A Rock and a hard place (The Economist)
We are witnessing a great betrayal of Iraqi Christians (The Catholic Herald)