After the traumas inflicted by the rise of ISIS, the return of Iraq's Christian communities to villages and towns on the Nineveh plains around Mosul has a special resonance throughout the Catholic Church.

For one priest and active supporter of his fellow Catholics in Iraq, the resettlement should represent something joyful but instead the threat these Iraqis faced has not disappeared but only changed form.

Father Benedict Kiely left his comfortable posting in the American state of Vermont to work with Iraqi Christians, a community that was 200,000 strong in Mosul and surrounding towns and had been put to flight by the terror group.

ISIS has since been vanquished but Fr Kiely on a recent visit experienced the culture of fear that still exists at first hand. One of his friends, Fr Behnam Benoka, a Syrian Catholic priest, recalled to him how a member of an Iran-backed Popular Mobilisation Forces (PMF) militia put a gun to his head after surrounding his church in the town of Bartella.

"They feel surrounded in Bartella, the priest has had a gun in his face, there is a large banner of the ayatollahs in the middle of the town and even the Iraqi general in the area seems afraid of these militias," Fr Kiely told The National from his home in England after returning from Iraq. "Unless the Shia militias are removed, it's basically over for Christians in the area.

"As Fr Benoka said to me: there's bad and there's worse, which would you rather live in?"

As Pope Francis prepares to make a groundbreaking visit to the Arabian Peninsula, the plight of Iraq's Christians is sure to feature at the top of the agenda.

At Christmas the Vatican's second-most senior official travelled to Iraq to show solidarity with the community. Cardinal Pietro Parolin visited Baghdad, Erbil and Mosul and tried to draw a line under the troubles of the congregation.

"You are a Church of martyrs," Cardinal Parolin said at a Mass. "The blood of your martyrs and the witness of faith given by so many of your brothers and sisters represent a treasure for the Church and a seed of new vitality."

Engagement with the Iraqi government over the need to nurture and rebuild Catholic parishes has been of limited benefit so far. Of the 45 churches in metropolitan Mosul, none have been re-opened for daily use.

Any acts of worship have been one-offs. Mosul's Christian community that in living memory numbered in the hundreds of thousands is now estimated by Fr Kiely at just 10 families. The streets are still littered with bodies and ghoulish reminders of the battle to drive out ISIS, including clumps of hair among the rubble after the fighters shaved off their beards to flee.

Painfully, Fr Kiely recalls that the churches were used as execution grounds during the battle. "I was first inspired back in 2014 when the reports came out that for the first time in almost 2,000 years there was no Mass said in Mosul," he said.

Speaking of the situation in Bartella, he said: "Less than half the Christians have returned and the power of the Shia militias is putting even this in peril. It's an army within an army and there are many instances of intimidation."

He accuses the PMF, also known as Hashed Al Shaabi, of attempting to engineer a new and permanent demographic change in the area by settling communities of the Shabak minority in the towns and farmland, not in the more marginal hinterlands where they lived before the rise of ISIS.

It is the settlers who have assisted the PMF patrols and welcomed the banners proclaiming loyalty to Iranian and Iraqi religious leaders.

"The church leadership has been very robust in its concern for the persecuted Christians but it remains very difficult to secure action and support from the Iraqi government in the face of everything that is happening," he said.

The Christian community was long in decline, even before the overthrow of Saddam Hussein following the American invasion in 2003. The violence and cycles of terror that followed the collapse of the regime uprooted tens of thousands of Christians in Baghdad, Mosul and elsewhere in the decade before ISIS came on the scene.

Fr Kiely welcomes the US assistance on offer to rebuild towns like Qaraqosh, which has a church and a cultural centre newly built, but wants more American diplomatic activity directed at the Iraqi government.

"The Iraqi government must be put under pressure to remove the Popular Mobilisation Forces, after all the Americans provide all the money and that means leverage," he said. "The Iraqi government must stand up to the Iranians to get them to pull out of the area."

Only in neighbouring Erbil could there be said to be a thriving Iraqi Christian community, which owes much to the charismatic leadership of the Chaldean Christian Archbishop Bashar Warda.

The Catholic Church under Archbishop Warda's leadership has established the Nineveh Plains Reconstruction Project to oversee reconstruction, relying on funding from the Vatican's papal foundation, the charity Aid to the Church in Need and groups such as the American grassroots body, the Knights of Columbus.

Fr Kiely runs his own small charity, Nasarean.org, which seeks to help Christian returnees establish new livelihoods. He understands that many in the community are looking for refuge elsewhere but also says they need help if they are going to stay in their homeland.

"What I say is help those who want to stay to stay, help those who want to leave to leave," he said. "There are no jobs and there is no security. They are more fearful than they were before the defeat of ISIS."

By providing micro-finance loans and grants, he has helped with the establishment of bakeries, garages in sewing businesses. As these become established, he also prays that the situation for Iraq's beleaguered Christians will improve.

"They're pawns in this fight between the Kurds and the Iraqi government and the Iranians. No one is defending them."