The human cost of the Mosul offensive – and of Islamic State's brutal two-year occupation – is not yet known. But the Iraqi city's cultural treasures have already suffered a grave toll.
Satellite imagery, eyewitness testimony from escaping civilians and boastful videos from Islamic State have provided clues as to the extent of damage to ancient sites and artifacts in Mosul. But experts say a full reckoning is probably months away, and remaining historical riches are still in danger from fighting.
The world got a dismaying glimpse of Islamic State's appetite for destruction of antiquities in February 2015, when the group released online footage of sledgehammer-swinging extremists rampaging through Mosul's central museum, smashing statuary and toppling friezes. Some were replicas, but others were believed genuine – and priceless.
Prior to capturing Mosul, Islamic State had made a regular practice of wrecking historic sites as it seized swaths of Syrian and Iraqi territory – taking particular aim at shrines associated with religious minorities such as Christians and Yazidis, or those revered by Shiite Muslims, all of whom Islamic State regards as heretics.
But it was the Mosul museum attack that put the group on the map when it came to large-scale cultural destruction, embodying Islamic State's puritanical vision of Islam and symbolizing Western powers' inability to protect precious sites and objects in its path.
"The big spectacular events that they video are basically propaganda, to give the idea that they can act with impunity," said Amr al-Azm, a professor of Middle East history and anthropology at Shawnee State University in Ohio.
Northern Iraq, a wellspring of successive ancient civilizations including the Assyrian and Akkadian empires, is a trove of antiquities. Nearly 1,800 of Iraq's registered archaeological sites lie in areas that are or have been under Islamic State's control.
Experts say the wave of wreckage amounts to cultural cleansing – a deliberate bid to erase the traces of centuries of sectarian coexistence, a notion that is anathema to Islamic State.
"The destruction is not just of physical structures – it's the texture of the city and the lives of its different communities," said Bernard Haykel, a professor of Near Eastern Studies at Princeton University.
And Islamic State is known to have reaped significant revenue from black-market trafficking in archaeological relics. The group "considers antiquities a natural resource, like mining or oil," said Christopher Jones, a Columbia University historian who has documented cultural damage in the region on his blog.
Because Mosul and nearby villages in Iraq's Nineveh province have been largely cut off from the outside world since the group seized control in June 2014, the status of many important sites is not known, but those who work in the field are assuming the worst.
As Iraqi and Kurdish attackers close in on Mosul, Islamic State militants may choose to fight from within areas such as the Old City, which is dotted with historic mosques and structures, said Michael Danti, a Boston University archaeology professor who is in Iraqi Kurdistan for fieldwork.
"It is a dense clustering of historic neighborhoods with narrow alleyways and streets – I would suspect that Daesh will use this area to hole up and resist the offensive," said Danti, using the Arabic acronym for the group. "That has the potential to cause severe damage."
The museum video may have grabbed the most headlines, but Islamic State's campaign of cultural destruction in the city began months earlier, almost as soon as the group had seized control.
In the early days of the occupation, ancient books and manuscripts, together with centuries-old Arab scientific instruments, were destroyed or looted. Mosul University's library was burned, and the city's main public library was blown up and the ruins razed.
Other targets in Mosul included a mosque dedicated to the prophet Jonah, who in biblical telling traveled to ancient Nineveh to warn of imminent destruction, which was then allayed by the city's repentance. Known in Arabic as Yunus, he was revered by many Muslims as well as Christians. But Islamic State forbade that veneration — and made that clear by blowing up the site.
And not all the destruction has been documented. Even in the case of the Mosul museum, the fate of the objects housed in halls not shown remains unknown. The slickly produced five-minute video opens with a Koranic verse on idol worship, before a narrator rails against polytheists and heretics, and the rampage begins.
In the museum video, the militants are also shown attacking the Nirgal Gate, an entrance to Nineveh, on the outskirts of present-day Mosul. At the massive gate, an icon of the wealth and power of the Assyrian empire, Islamic State fighters are seen determinedly smashing half-human, half-animal guardian statues.
The damage was not limited to Mosul and its immediate environs. The fortified city of Hatra, a UNESCO world heritage site 68 miles southwest of Mosul, was overrun by Islamic State fighters in 2014, and video showed the militants directing automatic-weapon fire at sculptures and structures. The site was then repurposed as an ammunition dump.
Looting and outright destruction have caused incalculable losses across Islamic State's self-declared caliphate in parts of Iraq and Syria. Irina Bokova, director general of the U.N. cultural agency, has said the group's deliberate campaign of cultural annihilation amounts to a war crime.
The months of occupation of the Mosul area have allowed Islamic State militants to take a leisurely approach to desecration and destruction, returning to some sites again and again, leaving no stone unturned.
"Unfortunately, in Mosul," said historian Jones, "it could be a matter of running out of things to destroy."