The rise of a self-proclaimed Islamic caliphate in parts of Syria and Iraq is already responsible for the eradication of Christianity in the historic city of Mosul, and this could be the first step toward much greater persecution in the weeks and months to come.

Even before the rise of the radical Islamists calling themselves the Islamic State, or ISIS, Christianity was greatly endangered in Iraq. Open Doors USA listed it as the fourth worst persecutor of Christians in the world earlier in the year.

"Iraq was already a very dangerous place for Christians because of the weakness of the central government and their inability or unwillingness to protect Christian churches and Christians who wanted to choose for themselves what their religious beliefs worse," said Open Doors USA President and CEO Dr. David Curry, who added that the latest developments in Iraq are making things exponentially worse.

Listen to the WND/Radio America interview with Dr. David Curry:

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On July 19, ISIS announced every Christian in Mosul had a choice by noon Saturday to convert to Islam, pay a financially crippling tax or leave with no possessions but the clothes on their backs.

"Since June 10, when ISIS came in and took over ... it's been incredibly difficult. Over 3,000 families, just from Mosul, are homeless, are on the run and have had to leave everything and it's really unprecedented in this modern age to have a group call out this kind of segregation of a religious minority and force them out of their homes with impunity. No Western government seems to be standing up or protecting these folks," Curry said.

Not surprisingly, the persecution is leading to a significant humanitarian crisis.

"Those that have the resources are heading out of the country entirely," he said. "Most of them, of course, don't have the resources to get on a plane and fly out, so they're heading north into the Kurdistan regions, where there is more security."

Open Doors USA is racing to meet the physical needs of those heading for an uncertain destination.

"Open Doors has set up response to help the refugees," Curry said. "We've got a project that is giving them food, water, tents, whatever we can do to help them stabilize in their homeless condition and try to acclimate them back into society if possible."

Curry said those who choose to turn a blind eye to the treatment of Christians in Iraq are making a horrific mistake.

"I think people underestimate how fast this kind of persecution spreads and to our detriment," he said. "This sort of persecution in the Middle East could certainly spread to other religious groups, like Jewish minorities, certainly Buddhist minorities. When we let this kind of aggression stand, I think it's a very bad sign for the rest of civilization."

Curry added, "I think you could see problems in Jordan. I think you could see problems in parts of Saudi Arabia and Kuwait. There's still key parts of Iraq. It certainly is a major shift in the Middle East. I think it could get worse."

That's why, Curry said, Western nations need at least to publicly condemn ISIS for this persecution.

"Governments need to stand up and send clear messages of support to the Christian minorities, to do what they can to put diplomatic pressure on these groups and to make this very difficult to happen anywhere else and to hopefully turn the tide in the coming weeks," he said.

The upheaval of the past 11 years is taking a severe toll on the Christian population in Iraq. Curry said there were a million believers in Iraq in 2003. Now he said some estimates are as low as 300,000.