For the past eighteen months, the University of Pennsylvania archaeologist Katharyn Hanson has been spending a lot of time analyzing satellite images from Iraq and Syria. As fighters from the Islamic State in Iraq and al-Sham (ISIS) overrun the region, they have been digging up many archaeological sites and looting whatever they find. “You get these sites that look like Swiss cheese, with all the holes,” Hanson said. “It’s just pockmarked.”

Thousands of vital archaeological sites—remains from Bronze and Iron Age settlements as well as from Islamic, Greek, Roman, and Byzantine civilizations—are now at risk. Humans built the first cities in the region, and some spots have been continuously occupied for more than six thousand years. “It’s a cliché, but it’s true. This is the cradle of civilization,” the director of research at the Penn Cultural Heritage Center, at the University of Pennsylvania Museum, Brian Daniels, told me.

Daniels and others say that ISIS, which controls large parts of both countries, appears to be doing much—although not all—of the digging. Hanson points to three Syrian sites, Apamea, Dura-Europos, and Raqqa, as places that have been particularly hard hit. Archaeological looting is common throughout the world, from Native American sites in the Southwest to jungle palaces in Cambodia, but the pillage in Iraq and Syria is singular in its invasiveness. “They just break the places open,” the Syrian archaeologist Amr Al-Azm, a professor at Shawnee State University, in Ohio, who lived and worked in Syria for many years, told me.

In Iraq, looting has been a serious problem for parts of the past decade. During a particularly violent period roughly between 2003 and 2006, organized looters took advantage of the chaos to pilfer many sites, especially ones in southern Iraq. But, according to Hanson, who is cataloguing the looting in both countries, most of the earlier activity was hand-digging rather than the bulldozing she’s seen from ISIS.

In much of Iraq and Syria, gathering information about these enterprises is difficult and dangerous. As with other lucrative illegal enterprises, those involved don’t take interference lightly. Daniels, Al-Azm, and Hanson get information through a network of sources, many of them current or former archaeology graduate students and museum workers...