Najeeb Michaeel, 63, was inaugurated in a ceremony in Mosul's St. Paul Church attended by Catholic leaders from the region and the US, as well as local officials and residents.

"Our message to the whole world, and to Mosul's people, is one of coexistence, love, and peace among all of Mosul's different communities and the end of the ideology that Daesh (IS) brought here," Michaeel told AFP.

Michaeel entered religious life at 24 and spent years serving at Al-Saa Church (Our Lady of the Hour) in Mosul.

There, he managed the preservation of nearly 850 ancient manuscripts in Aramaic, Arabic and other languages, as well as 300-year-old letters and some 50,000 books.

In 2007, he transferred the archives to Qaraqosh, once Iraq's largest Christian city, to protect them during an Islamist insurgency which saw thousands of Christians flee Mosul.

And when IS -- who was notorious for defacing churches and destroying any artefacts deemed contrary to its neoconservative interpretation of Islam -- swept across Iraq in 2014, Michaeel again took action.

As the jihadists charged towards Qaraqosh, the Dominican friar filled his car with rare manuscripts, 16th century books and irreplaceable records and fled east to the relative safety of Iraq's autonomous Kurdish region.

With two other friars from his Dominican order, Michaeel also moved the Oriental Manuscript Digitisation Centre (OMDC), which scans damaged manuscripts recovered from churches and villages across northern Iraq.

From the Kurdish capital Arbil, he and a team of Christian and Muslim experts digitally copied thousands of Chaldean, Syrian, Armenian and Nestorian manuscripts.

Iraqi forces recaptured Mosul from IS in the summer of 2017, and Michaeel returned to the city months later to attend the first post-IS Christmas mass.

He found his church in ruins, with rooms transformed into workshops for bombs and explosive belts and gallows had replaced the church altar.

But he insisted there was reason for hope.

"I'm optimistic. The last word will be one of peace, not the sword," Michaeel told AFP last year.

On Friday, the head of the Chaldean Catholic Church called for more international support to Iraq's Christians.

"Bishops from outside Iraq are participating in this occasion to support the Christians of Mosul," said Patriarch Louis Raphael Sako.

"They are encouraging them to return to their city, rebuild it alongside the other communities and turn a new page based on trust and peaceful coexistence."