PALMYRA, Syria, Dec. 21 (UPI) -- Since the Sunni extremist group known as the Islamic State came into prominence last summer, it has cut a path of violence and destruction through Iraq and Syria, often funding its militant activity through the black-market sale of looted antiquities.
The group has killed and publicly executed thousands of people as local groups and the international community -- even traditional rivals -- have concentrated efforts to defeat the militant organization.
But IS -- also identified as Daesh, ISIS and ISIL -- has gained notoriety for more than the human cost of their self-declared caliphate. Throughout 2015, the militants, citing the charge of "idolatry," have destroyed several ancient archaeological sites within the boundaries of their captured territories.
Experts say the black-market sale of antiquities from such sites adds to the group's revenue and thus its ability to keep its military operations alive.
The U.S. Federal Bureau of Investigations earlier this year warned art dealers to be on the lookout for pieces that may have been sold into the market by IS, and the United Nations Educational, Scientific and Cultural Organization said IS forces control one-fifth of Iraq's 10,000 internationally recognized heritage sites and are looting them "on an industrial scale."
"Cultural cleansing, in my view, is exactly what's happening in Iraq," UNESCO chief Irina Bokova said in July. "These extremists want to impose a different vision on the world. They want to tell us that there is no memory [of these sites], that there is no culture, that there is no heritage."
UNESCO said it is using satellites to monitor threatened sites in IS territories, and in November, French President Francois Hollande offered to have antiquities transported from Syria to France for safe keeping.
Most recently, an IS affiliate gained control over one of the world's best-preserved ancient Roman theatres in the Libyan town of Sabratha, stoking fears of further looting and destruction.
What follows is a list of documented instances in which IS forces destroyed ancient sites and artifacts in 2015.
February: Artifacts at the Mosul Museum in Iraq
IS released a video showing militants using sledgehammers, jackhammers, power drills and pickaxes to dismantle priceless 3,000-year-old artifacts at Iraq's Mosul Museum. Some of the sculptures and statues dated back to the Assyrian Empire, which existed in the region from 2500 B.C. to 605 B.C.
"These ruins that are behind me, they are idols and statues that people in the past used to worship instead of Allah," one man said in the video. "The Prophet Muhammad took down idols with his bare hands when he went into Mecca. We were ordered by our prophet to take down idols and destroy them, and the companions of the prophet did this after this time, when they conquered countries."
IS members also burned 100,000 documents from the museum's priceless collection of rare books and manuscripts, including works from the Ottoman Empire.
In addition, Qais Hussein Rashid of Iraq's Tourism and Antiquities Ministry said the militants destroyed two important sites in the city: the shrines of Ibn Al-Atheer and the Prophet Yunus.
March: The ancient Assyrian city of Nimrud in northern Iraq
IS militants used a bulldozer to cause extensive damage to a site containing the ruins of the ancient Assyrian city of Nimrud. Built in the 1200s B.C., the location featured carvings depicting tales of ancient King Ashurnasirpal II, who made the city his capital in the 800s B.C.
U.N. Secretary-General Ban Ki-moon called the incident a "war crime" and "an attack on humanity as a whole."
"This is yet another attack against the Iraqi people, reminding us that nothing is safe from the cultural cleansing underway in the country; it targets human lives, minorities, and is marked by the systematic destruction of humanity's ancient heritage," Bokova said at the time.
April: The ancient city of Hatra, Iraq
IS released another video, this one showing militants using sledgehammers and assault rifles to destroy artifacts in the city of Hatra, in Iraq's Nineveh province. Earlier reports in March suggested IS forces used a bulldozer to damage the 2,000-year-old ruins, which are a UNESCO world heritage site.
According to UNESCO, Hatra was a "large fortified city under the influence of the Parthian Empire and capital of the first Arab Kingdom." The city "withstood invasions by the Romans in A.D. 116 and 198 thanks to its high, thick walls reinforced by towers."
The architecture of Hatra comprised a mixture of Hellenistic and Roman designs mixed with Eastern decorative features.
"We will destroy your artifacts and idols anywhere and Islamic State will rule your lands," one of the militants in the video said.
June: The tomb of Muhammad bin Ali and the shrine of Shagaf in Palmyra, Syria
Following the militants' capture of the ancient ruins of Palmyra, Syria, in May, IS forces reportedly began planting explosive devices amid the site, which contains 2,000-year-old Roman colonnades.
The following month, IS published photos depicting the demolition of the tomb of Muhammad bin Ali, a descendant of Ali bin Abi Taleb, who was a cousin of the Prophet Muhammad. The militants also detonated the shrine of Shagaf, or Abu Behaeddine, a religious figure who died 500 years ago.
The tomb of Muhammad bin Ali was located more than 2 miles north of Palmyra, and the shrine of Shagaf was in the city's Arch of Triumph.
July: The Lion of al-Lat in Palmyra, Syria
Maamoun Abdelkarim, Syria's director of antiquities, said IS militants destroyed the Lion of al-Lat, a 2,000-year-old statue of a 10-foot tall lion located in Palmyra. At the time, he characterized the incident as "the most serious crime [IS has] committed against Palmyra's heritage."
Around the same time, the Syrian Observatory for Human Rights, a Britain-based activist group monitoring Syria's civil war, said IS forces caught a man in Aleppo province with about six artifacts he had allegedly smuggled out of Palmyra. The militants publicly whipped the man and forced him to smash the objects in front of onlookers.
The Observatory noted it was not clear whether the antiquities were authentic or if IS used replicas in order to sell the real items on the black market.
August: The St. Elian monastery in Qaryatain, Syria
IS published photos showing the St. Elian monastery, a fifth-century Christian structure, reduced to rubble. The militants reportedly used bulldozers to destroy the complex, which was located in the city of Qaryatain, in Syria's Homs province.
A headline on the photographs reportedly read, "Mar Elian monastery, worshiped without God."
The monastery had been restored 10 years earlier by Paolo Dall'Oglio, head of the ancient Mar Musa al-Habashi monastery in nearby Nabk. In 2013, IS was reported to have kidnapped Dall'Oglio, who is presumed dead.
August: The Temple of Baal Shamin in Palmyra, Syria
According to SOHR, IS demolished the temple of Baal Shamin, or "Lord of the Heavens," in July. Quoting narratives of people who escaped Palmyra, the Observatory reported the militants rigged explosives onto the temple, located near Palmyra's famous Roman theatre, before eventually detonating it.
The following month, IS published photos of the 2,000-year-old temple disappearing amid a huge cloud of smoke and debris.
August: The Temple of Bel in Palmyra, Syria
Initial reports indicated IS forces failed in an attempt to demolish the Temple of Bel, a 2,000-year-old Roman-era structure located in Palmyra. At the time, Abdulkarim characterized the damage as "partial" and said "the basic structure is still standing."
However, satellite images in early September showed the militants had, in fact, succeeded at reducing the temple to rubble.
"We can confirm destruction of the main building of the Temple of Bel as well as a row of columns in its immediate vicinity," The Guardian quoted the U.N. as saying at the time.
October: Prisoners detonated on colonnades in Palmyra, Syria
In a grotesque display of multi-tasking, IS detonated explosives on three prisoners strapped to columns amid the ancient ruins of Palmyra. SOHR, which reported the incident, said at the time that the executions were the first of their kind and that IS forces were becoming more creative in their methods of killing prisoners. The militants ran a tank over a Syrian soldier who allegedly did the same to dead IS fighters. IS also reportedly killed detainees after forcing them to dig graves with their own hands.
Two months earlier, IS publicly beheaded 82-year-old Khalid al-Asaad, a renowned scholar of antiquities who had worked as the director general of the Palmyra Directorate of Antiquities and Museums for over 50 years. Asaad had reportedly refused to reveal the location of various artifacts sought by the militants.