GAZIANTEP, Turkey -- Among the tragedies of the conflict between the two branches of Islam is the destruction of irreplaceable art in Syria, a nation that was once one of the world's great museums of antiquity.
A seventh-century mosque is blasted by a shell.
The ancient city of Apamea, dating back some 2,300 years, is seen in satellite photos in 2011, now pockmarked with the so-called robber holes of looters.
Priceless funeral busts from Palmyra, a World Heritage site, stolen from their tombs.
It's what compelled Syrian-British archaeologist Dr. Amr al-Azm to organize his former colleagues and students inside Syria. Together they launched an effort to protect what could be salvaged and to create a record of what could not.
"Some of them were once museum curators, archaeologists who feel passionate about their own culture, their own history, and their own country, and they feel it is part of their duty, their responsibility to protect this cultural heritage," said Al-Azm.
Armed only with cellphone cameras, notepads and sandbags to protect fragile mosaics and artifacts, Al-Azm's men routinely brave regime shells and snipers and travel through dangerous ISIS territory.
Al-Azm says selling antiquities on the black market has become a major moneymaker for ISIS.
"Digging by hand is one thing," he said, explaining the process. "Digging by machine is extremely dangerous. They're bulldozing to move as much earth as possible in order to sieve it and get the artifacts out," he said, noting that the process is very lucrative for the extremists.
When shelling damaged a museum in his hometown, volunteer Ayman Inabu led a team to protect its invaluable contents.
"Antiquities represent our heritage, our identity," said Inabu. "Those who have no history, have no future. In the beginning I was afraid, but if we die at least future generations will testify about what we have done."
But Al-Azm says with the scale of the damage being done, his side is not winning. So why does he do it?
"Because it's better than doing nothing," he said. "My daughters will ask me the question: What did you do in the war? What did you do to save something that you believed was very important? And I would be ashamed to say to them that I did nothing," he said, his lip quivering. "Shameful. I can't. You have to do something."
A duty to prevent a great loss, not just for Syria, but for the world.