This time it is the ancient oasis city of Palmyra in Syria, a UNESCO World Heritage Site dating back 2,000 years.  Syrian government troops have reportedly been fighting to contain ISIS fighters after they launched an attack Wednesday on Tadmur, the modern town near the ruins of Palmyra.  Clashes between Syrian forces and ISIS militants near the ancient city left at least 15 Syrian fighters dead Friday, according to the London-based Syrian Observatory for Human Rights.  ISIS is reported to have executed 23 family members of Syrian government workers Friday in al Amriya, according to SOHR. The group also says ISIS executed 26 people in al Amriya and nearby al Sukhna on Thursday. Both villages are about 45 miles (70 kilometers) northeast of Palmyra.  This push has prompted fears that if the Palmyra ruins fall under ISIS control, the group will destroy it, just as it bulldozed the ancient Assyrian city of Nimrud and took sledgehammers to statues in Mosul Museum.  Syrian director of antiquities Maamoun Abdul Karim told AFP: "If ISIS enters Palmyra, it will spell its destruction."  UNESCO Director-General Irina Bokova called for the protection of the site.  "The site has already suffered four years of conflict, it suffered from looting and represents an irreplaceable treasure for the Syrian people and for the world," she said in a statement.  Palmyra, also known as the "bride of the desert," is an exquisite collection of ruins in the desert northeast of Damascus.  Situated in an oasis, Palmyra was once a monumental city sitting on an important trade route linking Persia, India and China with the Roman Empire.  Its history as an important caravan city at the crossroads of ancient civilizations is reflected in the eclectic mix of architectural styles found among its colonnades and temples.  British historian and novelist Tom Holland describes the site as "an extraordinary fusion of classical and Iranian influences intermixed with various Arab influence as well."  Destruction of Palmyra wouldn't just be a tragedy for Syria, it would be a loss for the entire world, he adds.  "This isn't just about Middle Eastern history, these are the wellsprings of the entire global culture. Mesopotamia, Iraq, Syria, this is the wellspring of global civilization. It really couldn't be higher stakes in terms of conservation."  Prof. Fawas Gerges of the London School of Economics, whose forthcoming book, "ISIS: A Short History," looks at the terror group, says that it takes opportunities when it can.  "It is looking for the soft bellies, the weakest spots ... and the Syrian army didn't have any major troops there."  "Of course, capturing cities and towns provides them with resources. It's the war economy," he said.  According to nonprofit news organization Syria Direct, the Syrian regime considers the modern town at the site "the first line of defense" against ISIS attacks from the eastern regions.  They also report that the town is a point of defense for surrounding oil and gas fields, including the Shaer gas fields, important for Syria's electricity sector.  Centrally located, control of this area would also give ISIS a clean line down the highway to Damascus and up to Homs.  This is not the first time ancient sites have been destroyed during Syria's brutal four-year civil war.  Notable casualties include 11th century crusader castle Crac des Chevaliers; its walls were severely damaged by regime airstrikes in 2013.  Aleppo Souk, a formerly thriving part of Syria's economic and social life, was severely damaged in a fire in 2012.  "What is distinctive and horrendous about IS' mode of operation is that they are deliberately going out of their way to destroy (ancient artifacts)," says Holland.  Tracking ISIS' trail of historical obliteration  ISIS propaganda claims the Islamist militants are destroying idols or false gods and following in the footsteps of the Prophet Mohammed, who smashed statues in Mecca.  The terror group is media savvy and knows that bulldozing ancient sites will make the West sit up and take notice.  "They depend on the sugar rush that comes from staging atrocities and they know that one way to get Western attention ... is to destroy ruins that have a particular place in the heart of the entire world," says Holland.  Hypocritically, ISIS sells the artifacts for huge profits.  "They have networks that allow them to traffic in cultural treasures," says Gerges. "They have made tens of millions of dollars selling artworks."  It's not a separate issue, argues Holland.  "If you think about the Nazis, they destroyed synagogues as well as the people who worshiped in them," he says, adding that Palmyra was a melting pot where different cultures met and fused.  "So, it's the perfect embodiment of what Syria was before this devastating civil war began."  Gerges said that ISIS is trying to culturally cleanse the land -- both diversity among people and cultural diversity.  Diversity goes against ISIS' very ethos and foundation.  "They want to cleanse the land, literally, whether it's Christians, Kurds, Yazidis."  Or the ancient treasures built by them.  CNN's Samira Said contributed to this story
Another world wonder is on the brink of destruction as ISIS continues its rampage through the cultural heritage of Iraq and Syria.