"Everywhere militants were blowing up Christians... the message to these 'infidels': You don't belong in Iraq. Leave, pay the penalty to stay, or be ready to die."

Journalist and editor of WORLD magazine, Mindy Belz, has reported on the ground in the Middle East for more than a decade. Having travelled extensively in and around Iraq since before the beginning of the Iraq invasion of 2003, she's had an insider's view of the way that the war has affected civilians, in particular Christians.

The ultimatum above features on page one of her new book, They Say We Are Infidels (Lion Hudson, £12.99). It refers to war-torn Iraq in 2006 – long before the catastrophic rise of Islamic State – and reveals the heartbreaking decision faced by Christians all over Iraq and Syria.

A believer herself, Belz has compiled the harrowing, and often inspiring, accounts of the Christians she's met throughout the region while covering the war and its aftermath. People like Insaf Safou, an Iraqi Christian wife and mother who travelled throughout the country with packets of donated money to give to families in desperate need. Odisho Yousif, who was shot and kidnapped by Islamist militants in 2006 while trying to deliver aid. And Fr Najeeb Michaeel, who packed up and transported hundreds of ancient, priceless documents from his church in Mosul which was later overtaken by ISIS militants, and is now working to preserve church history by digitising them.

Belz says she "stumbled upon" the persecuted Christians of Iraq and was drawn in by their resilience. "It's embarrassing to admit because I am a Christian and should have been more aware of the ancient roots that our religion has there, and yet I wasn't," she tells Christian Today. "I began a whole long journey that I didn't expect; it was a door opening onto a community that I think most of us in the West have little appreciation and understanding of."

Christians have long been persecuted in the Middle East. Though the world woke up to the plight of religious minorities in 2014 with the overrunning of Mosul, they had suffered for years under brutal regimes and extremist groups. "We didn't fully pay attention... until ISIS came in in 2014 and started beheading people, hanging Christians on crosses, taking women as slaves and doing all of these unspeakable, atrocious things," Belz said. "[This is the] kind of persecution that Christians have been facing all along. They haven't had a seat at the table, their voices haven't been heard."

Belz has kept travelling to the region because she was amazed by not only the resilience, but the good humour of the Iraqi Christians she met. "I was just amazed by how much they were suffering, and how much they continued to endure it. How they kept starting schools, kept on holding worship, and starting new churches," she says. "Their families were bombed, they had to leave [their homes], but they started a new church, started a new business, [connected] with others who had been through similar misery and maintained their faith in the midst of all that."

The persecuted, and persevering, Church

They Say We Are Infidels sheds light on how the ongoing political crisis in the Middle East has intensified persecution for some of its most vulnerable groups. Belz offers an overview of the complexities of war-torn Iraq and Syria, but gives it a human face.

Despite the suffering she's witnessed, however, she is insistent that Iraqi Christians aren't simply to be given our sympathy. "So often when we talk about the 'persecuted Church' in the West, we think of something far away, something exotic, and we give it our pity," she explains. "I think of the persecuted Church more as a persevering Church – certainly something that needs our help, but also something that needs respect. People who have endured, and who we can learn from. There is so much in the West we can learn from what they have been through and how they have continued to 'try to make water in the desert'."

She's adamant that she's "learned so much" from spending time with people who have given up everything for their faith in Christ. "I've learned both about the human experience, and as a Christian what it means to turn the other cheek, really, truly to do that, and to continue to trust in Jesus Christ when life is not rewarding you.

"They truly are considered infidels," Belz continues. Though ISIS laid out the extremist position on other faiths in 2014, she traces the brutal harassment as far back as 2003, when "Christians showed me these letters that were put under their doors threatening them, accusing them of being infidels, and telling them if they didn't convert or leave they would be killed. They promised their heads would be chopped off, and their children's too, it was very graphic."

During her travels, Belz has met many Christians who are determined to stay in Iraq and Syria to make sure the faith remains rooted in its birthplace. But she's worried for the future. "I have concerns... that the vibrancy of the Christian community will diminish to the point that it will lose its place in the [wider] community. Sadly, we can already see this happening to a great degree," she said.

Before the Iraq war, there were more than one million Christians living in the country. Now  there are believed to be fewer than 150,000.

"The demise of Christianity, you could argue, has already happened," she says.

She recalls a senior Church leader in Aleppo telling her that the Christian community needs to maintain its presence in the Middle East, "not only because it's the birthplace [of Christianity] but because there are others who need us. Muslims need us, our witness, our testimony, our coming along side and being the 'other''.'

"And that's a really hard word," Belz says. "Because being the 'other' in that part of the world can get you killed."

Christians have fractured over whether to stay or leave, and yet Belz says she's seen the Church unite in ways that seemed impossible before the persecution began. Tensions between the older Catholic, Orthodox and Chaldean Churches and the newer evangelical churches have "melted away" and churches are offering help indiscriminately to those who need it – whether they're Christians, Muslims or Yazidis, a minority religion considered devil worship by ISIS.

"This is unique," Belz says. "Churches are not simply serving Christians, which takes a lot of courage on both sides. It takes a lot for a Muslim family to show up on the church doorstep and ask for help. This is one of the things God has been doing through this situation."

She believes the Church has risen to the challenge of serving the midst of a terrible situation, whether by providing food and shelter for the poor and displaced, opening medical clinics or serving at homes for the disabled.

"It's very hard to keep [the Church] down," she says.