MAR MATTI MONASTERY, Iraq – As Islamic State group militants advanced toward this monastery perched on a mountain in northern Iraq, the monks rushed to protect a cherished piece of their heritage: Their library of centuries-old Christian manuscripts. Dozens of the handwritten tomes were spirited to safety in nearby Kurdish-ruled areas.

There they remain, hidden in a non-descript apartment in the Kurdish city of Dohuk where Christians who have fled the extremists’ onslaught are living and watching over them.

The Associated Press was allowed rare access to the library, a collection of copies of Bibles and biblical commentaries, mostly written in Syriac – a form of the ancient Semitic Aramaic language – and mostly dating back 400-500 years. The oldest is a copy of the letters of Saint Paul, some 1,100 years old. The bound tomes, some with tattered pages written in black and red ink, lay on shelves.

Their rescue is a bright spot in the devastating onslaught by the Sunni extremists against Iraq’s people – particularly religious and ethnic minorities – and Iraq’s heritage, as they took over much of northern and western Iraq the past year.

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When they captured Iraq’s second largest city, Mosul, and other parts of the north last summer, most Christians and other minorities fled the city and nearby towns for the Kurdish autonomous zone further north. The militants seized churches and monasteries in and around Mosul, removing symbols of Christianity like the cross and blowing some up. They have also attacked Sunni Muslim shrines they consider idolatrous. In recent months they have accelerated their campaign to destroy more ancient sites, like the 3,000-year-old ruins of Nimrud; they shattered artifacts in Mosul’s museum and burned hundreds of books at Mosul’s library and university, including rare manuscripts.

The Syriac Orthodox Christians of Mar Matti, a monastery that dates back to the 4th century, moved to rescue their library of around 80 manuscripts in August, at the height of the Islamic State group’s blitz, when its fighters were bearing down from Mosul to the north, toward the monastery, 35 kilometres (20 miles) from the city. Their advance was halted by Kurdish pershmerga fighters, who now hold the road leading to the monastery.

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That was a relief to the monastery’s monks and their community. But they aren’t taking any chances and are leaving the manuscripts where they are until the group is decisively defeated.

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“Thank God they were unable to reach the monastery,” said Raad Abdul-Ahed, a local Christian who helped transport the library. But “we will keep it here until the crisis is over, until the situation is stabilized.” Abdul-Ahed, who fled his hometown near Mosul, now lives in the apartment with the manuscripts.

Still, their absence leaves a void – sentimental and practical – for the handful of monks who continue to live at Mar Matti, along with seven Christian families who have taken refuge there after fleeing their nearby town of Bashiqa. They can still see their houses – just a 10 minute drive away down the mountain – but they can’t return since it’s still held by the Islamic State group’s fighters.

The monastery used to get throngs of visitors – nearly 2 million a year from around Iraq, the monks say. Now it’s too dangerous, and the only visitors are Kurdish fighters, taking a break from battle to take pictures of the site.

Ancient manuscripts, some of them over a thousand years old, are being held in a bookcase in a location in the city of Dohuk, northern Iraq. (AP Photo/Bram Janssen)

The Syriac Orthodox archbishop for northern Iraq, Saliba Shimon, now lives at the monastery after fleeing his home village outside Mosul. There, he teaches Syriac to students. Unfortunately, the rich trove of Syriac tomes is no longer there for him to use. He wanders through the empty library room, showing where the manuscripts used to be.

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He says many other Christian manuscripts that were scattered in churches in villages around Mosul are now lost after the militants overran the areas. He and other bishops managed to bring only a few as they fled.

“Each manuscript has its own spiritual value,” he said. “When we keep the manuscript, we are not doing it for the sake of its financial value, but rather because of its spiritual value.”

WATCH BELOW: ISIS destroys another significant historical site in Iraq