“We’re ridding the world of polytheism, and spreading monotheism across the planet,” an ISIS preacher recently said in a video recording. Behind him one could see the ISIS faithful using sledgehammers, bulldozers, and explosives to destroy the eighth-century-BC citadel of the Assyrian king Sargon II at Khorsabad, ten miles northwest of Mosul in northern Iraq, and the colossal statues of human-headed winged bulls that had guarded it. Amir al-Jumaili, an antiquities professor at Mosul University, has recorded the destruction of some 160 sites by ISIS since June 2014, when it conquered Iraq’s second city. He showed me some recent entries in his logbook:

5 March 2015—Nimrud destroyed; 6 March 2015, Hatra destroyed; 9 March 2015, Khorsabad destroyed [i.e., the fourth capital of the Assyrians].

The full extent of the damage to these enormous and remote sites remains unclear. But on March 18, 2015, Iraq’s distraught archaeologists and antiquities experts gathered for a government-sponsored conference in Baghdad. Iraq has 12,000 archaeological sites—too many to protect, I was told by Ahmed Kamel Mohammed, the director of the National Museum of Iraq in Baghdad, the country’s greatest collection of antiquities, which had been looted when the Americans took Baghdad in 2003. Some of the experts proposed drafting a UN Security Council resolution to entrust the protection of the sites to the US-led coalition. Others advocated the creation of a national antiquities guard. Iraq’s national security adviser, Faleh Fayadh, promised to consider this and then nodded off during a presentation about the ancient temple to the sun god at Hatra, one of ISIS’s reported targets.

Islamic heritage has fared no better. In the 1920s puritanically strict Sunni fighters, who were followers of the eighteenth-century religious leader Muhammad ibn al-Wahhab and allies of the Saudi tribes, cleansed Mecca and Medina of saint-worship following their takeover. So their ISIS successors today set off explosions that demolished over a dozen mosques in Mosul. These included the Nithamiya, a twelfth-century Seljuk madrasa, which they razed because it contained a shrine to Ali al-Asghar, the youngest child of the great Shia imam Hussein, killed in the seventh century. Over two days in February 2015, al-Jumaili noted in his log, ISIS also set fire to Mosul’s public library and theater.

Some observers of ISIS say they find similarities between its cultural devastation and other state-building projects in the cantankerous region. But other motives also drive its madness. Since the nineteenth century, archaeologists had sought permission to dig beneath Nabi Yunus, the hilltop shrine of Jonah that is Mosul’s landmark, in the hope of discovering the throne room of the Assyrian rulers reputed to lie below it. Perhaps, they speculated, it might house the loot Sargon II captured when he destroyed the Kingdom of Israel in the eighth…