For Iraq’s Christians, “the Surge” has been more like “the Purge” as ethnic and religious fighting continues to decimate this ancient and once-thriving Christian population. Before the U.S. invasion, Iraqi Christians numbered about 1.5 million. Now the figure is less than half that, due to expulsion, exodus, and murder. In March, the leader of the Chaldean Catholic Church, Archbishop Paulos Faraj Rahho, died while being held by kidnappers.

Now the situation in Mosul is growing especially dire. Reuter’s Vatican correspondent, Phil Pullella, reports today that the Vatican is calling on the Iraqi government and human rights groups to do more to protect Christians in Mosul, where half of the minority community has fled after attacks and threats.

In an interview with Reuters, Pope Benedict’s spokesman, the Reverend Federico Lombardi, said the Vatican was asking itself if there was “insufficient willingness” on the part of Iraqi authorities to protect Christians.

“We are extremely worried about what we are hearing from Iraq,” Lombardi said

Last Friday in Geneva, the U.N. refugee agency (UNHCR) said about half of the Christians in Iraq’s northern town of Mosul, nearly 10,000 people, had fled in the period of about a week.

“The situation in Mosul is dramatic. The victims are Christians and many thousands of people are fleeing precisely because they are subjected not only to the fear of periodic attacks but a systematic campaign of threats,” Lombardi said.

“This is extremely worrying and we ask ourselves if these people are sufficiently protected by the authorities or if the authorities are not able to protect them or if there is scarce willingness to protect them,” he said.

UPDATE: Via Catholic World News, the Chaldean Bishop of Kirkuk charges that Christians are being driven out of Mosul “for political reasons.” In this Asia News story, he sets out the political threats he sees in provisions being adopted now in Baghdad. I do not know what the U.S. stance is on minority protections, and if Washington will have any say, or wants to, given the stakes of this delicate political process.