ISIS has reportedly placed improvised explosive devices (IEDs) around the ancient ruins of Palmyra , in Syria, after recently capturing the adjacent city of Tadmur. The jihadi group has released images of the destruction of two shrines near the site.

The strategy for seeding Palmyra with IEDs has been debated: Is ISIS going to destroy the monuments, which they consider the creations of pre-Islamic idolaters, or is it an act to deter increasing airstrikes and an attempt by the Syrian army—which is now just six miles (10 kilometers) from Tadmur—to retake the city? ( Read how ISIS justifies destroying ancient sites ).

Michael Danti, co-director of the Syrian Heritage Initiative at the American Schools of Oriental Research, which is monitoring cultural damage in Syria and Iraq, reports that the pattern of IED placement appears to be optimized for “filmed destruction.”

Multiple independent sources confirmed to Danti that following the IED placement, ISIS members traveled around Tadmur using megaphones to announce their action to the terrorized populace. Over 15,000 residents have recently fled the escalating violence.

While the jihadis' ultimate motivation behind planting explosives in Palmyra remains unclear, the destruction of the shrines is part of the greatest systematic eradication of Islamic sites in modern history. In addition, the destruction of monuments from all periods and cultures in the ongoing conflict in Syria and Iraq is “the worst cultural heritage crisis since World War II,” says Danti.

View Images Jihadists have destroyed hundreds of rival Muslim sites, from Sufi shrines in Libya to revered tombs in Syria and Iraq. NG MAPS

While international attention has been primarily focused on attacks on ancient sites such as Nineveh and Hatra , the vast majority of the sites that are being destroyed in Syria and Iraq are from the Islamic era, according to Danti, who estimates there have been more than 100 “major heritage incidents” this year in Syria alone.

Other players in the ongoing Syrian conflict have been responsible for the deliberate or inadvertent destruction of Islamic sites and other cultural crimes, such as the looting of archaeological sites.

But the actions taken by ISIS are different because they’re so brazen and overt. “The destruction of cultural heritage has become part of the jihadi tool kit,” says Danti.

The shrines destroyed at Palmyra were the tombs of Nizar Abu Bahaaeddine, a Sufi scholar who lived there 500 years ago, and Mohammed Bin Ali, a descendent of the Prophet Muhammad's cousin, Imam Ali, and a site revered by Shiites. According to Danti, the shrine of Mohammed Bin Ali was destroyed last month, while the Sufi tomb was destroyed more recently. The images were bundled together for release to the international community.

Ushering in an “Unadulterated” Caliphate

The followers of ISIS practice a radical form of Salafism , a branch of Sunni Islam whose adherents strive to emulate the Prophet Muhammad and his followers and who claim to practice Islam in its purest, most unadulterated form. They support Sharia law, reject religious innovation, consider venerated tombs and shrines as symbols of idolatry, and view Sufis and Shiites as heretics.

Nancy Khalek, an assistant professor of Humanities and Religious Studies at Brown University, points out the irony: “ISIS is arguing that their view is not corrupted, but they’re doing so in a very ahistorical way. They’re claiming to be following a literal example, but they’re doing so in a very modern framework with the tools of modern warfare and institutions of modern nation states.”

View Images Extremists in Libya bombed this Sufi shrine on the outskirts of Tripoli in March 2013. ISIS and their allies say venerating such places promotes idolatry and violates Islamic law. Photograph by Stringer, Reuters

It’s been a year since the jihadists declared a Salafist caliphate, and their position on ‘idolatrous’ structures has resulted in the destruction of hundreds of Muslim cultural sites, from modest mud-brick Sufi shrines in Libya , to mosques belonging to the Turkmen minority population , to tombs of Biblical prophets recognized by Muslims as well as Christians and Jews. And the destruction is non-denominational: even a Sunni mosque complex that features a tomb can be considered too “ostentatious” for ISIS, according to Danti.

One alleged ISIS member has even threatened to destroy the Kaaba, Islam’s holiest shrine in Mecca, complaining that “[p]eople go to Mecca to touch the stones, not for Allah.”

The Strategy Behind the Theology

Aspirations of a pure, pious caliphate aside, there are several different theories around why ISIS is targeting Islamic sites. Dramatic images of spectacular explosions inspire recruits. By destroying buildings that have been at the center of a community’s religious life and venerated for centuries, the action can be considered a form of psychological as well as cultural warfare to keep local populations under heel.

“For the entirety of Islamic civilization, pilgrimage to local tombs has been an important aspect of [Muslim] social life,” says Khalek.

View Images Pilgrims in 1922 visit a 14th-century shrine revered as the tomb of the biblical prophet Jonah. ISIS militants blew up the site, located on the outskirts of Mosul, Iraq, in July 2014. Photograph by Eric Keast Burke, Nat Geo Image Collection

Targeting Shia mosques and shrines also foments continued sectarian violence, which creates the instability that the jihadi group takes advantage of. “[ISIS] is a parasite that thrives on chaos,” says Danti. “They embed themselves and make it painful to remove them.”

“People always think that [ISIS] is very pious and spiritual about the things that they do, but I think their selective destruction demonstrates a kind of hypocrisy,” adds Khalek. “Their motives are very pragmatic and more of a criminal enterprise than any kind of reflection of theological conscience.”

WATCH: National Geographic Archaeology Fellow Fred Hiebert discusses ISIS's recent destruction of artifacts and archaeological sites in Iraq and Syria.