For the French archaeologists Pierre Leriche, 73, and Jean-Claude Margueron, nearly 80, who both spent decades uncovering Syria's rich past, it is almost too painful to look at its grim present.
The civil war there has long made work impossible in the ancient cities, houses and temples where they once toiled peacefully to understand long-ago civilizations.
Now in Paris, an increasing number of reports are arriving that document the extent of the damage to one of the world's most important historical records, including physical destruction from the fighting, rampant pillaging of archaeological sites, and looting from museums and other collections.
The portrait emerging from scholars, the Paris-based United Nations Educational, Scientific and Cultural Organization, and experts in Syria is of a country in the process of obliterating its cultural history.
"The situation now is absolutely terrible there," said Mr. Leriche, a professor of archaeology at the École Normale Supérieure, one of France's most prestigious universities, who worked for more than 25 years at a site on the Euphrates River.
Noting reports of illegal excavation at about 350 places in that one site where he worked, he said: "They come with jackhammers. That means everything is destroyed."
Mr. Margueron worked at another Euphrates site, Mari, which dates back 3,000 years. "Mari was one of the first urban civilizations where man lived," he said in his modest apartment filled with traditional Arab furniture and carpets.
"If you pillage Mari, you destroy Mari. These are irremediable losses."
Mr. Leriche and Mr. Margueron are just two of many archaeologists from Belgium, Britain, France, Italy and elsewhere who spent years uncovering Syria's ancient history -- the world of the ancient Greeks, the Romans and the early years of Islam in the Levant.
Unesco is now trying to catalog and recover stolen Syrian artifacts, working with scholars, collectors and law enforcement authorities in bordering countries.
When the fighting began in 2011 there were at least 78 archaeological teams working in the country, and many included French-speaking scholars, in part a legacy of the French mandate in Syria and long cultural ties between the two countries, said Samir Abdulac, a Syrian who lives in France and is secretary general of the International Council on Monuments and Sites.
He is in touch with archaeologists from around the world who worked in Syria and believes they have an invaluable, if necessarily incomplete, reservoir of information about the destruction of the country's archaeological and artistic heritage.
Three types of destruction are occurring, said Mr. Abdulac and Nada Hassan, the chief of the Arab states unit for Unesco: destruction of archaeological sites by fighting; looting and pillaging at sites; and theft from museums -- with the latter the least serious so far, although there are reports of thefts at the Hama museum and several others, often carried out by highly professional thieves who appear to have come to seize specific pieces.
Particularly vulnerable to the fighting have been citadels and castles, which were often built on high points so that soldiers in ancient times could spot the approach of their enemy.
The same holds true today and rebels periodically claim sites, such as the famous crusaders' castle, the Krak des Chevaliers.
Then the Syrian Army fights to get it back, almost inevitably damaging the ancient walls, roofs and carvings. Sometimes sites change hands two or three times, each time suffering more damage from both sides.
The looting and pillaging has occurred largely in rebel-held areas, but also in contested places. When the fighting began and the foreign archaeologists left, the local guards, who often were no longer being paid, left their posts.
Local residents, who were jobless, then often dismantled the structures where archaeologists had stored as-yet unlabeled finds, such as pottery shards and small artifacts; they broke into on-site museums and stole the windows and doors, the wood used in the buildings' construction, the electrical wire and even pipes, according to the archaeologists.
The archaeologists said they did not blame the residents. "These are poor people in a crisis; one is worried for them," said Agnès Vokaer, the field director of the Belgian archaeological team at Apamea, one of the largest Roman and early Christian sites in Syria.
"There are no telephones, no electricity, there is no fuel for running agricultural machinery, there is no more food." The archaeologists are far more disturbed about what happened next. Foreign fighters soon arrived, and with them criminals who took a more ruthless approach.
By late 2011 or early 2012, depending on the site, they were working with mechanized digging equipment and jackhammers and had a seemingly clear idea of what they wanted, according to residents. They set up armed guards as lookouts while the illegal excavators went to work.
"We have approximately 1,000 people working every day to find coins, objects, to find something to sell," said Mr. Leriche of his site at Douros Europos, adding that the thieves worked with metal detectors burrowing into the ground whenever there were signs of metal.
They are digging as well for mosaics, said Ms. Hassan of Unesco.
Lebanon has intercepted 86 mosaics that were looted from Syria and returned them, but that is a tiny percentage of what archaeologists believe has been taken, she said. Ms. Vokaer, who worked for 10 years at Apamea before leaving in late 2010, described aerial views, taken in 2012, showing the site so pockmarked by holes -- evidence of illegal digging -- that it looked as if it had been barraged by mortar rounds.
"The houses had mosaics of great quality," Ms. Vokaer said. "The churches also had great mosaics and also the great colonnade was decorated with mosaics on the sidewalk."
As the war began, the Syrian government, worried that there would be a repeat of what happened in Iraq (where looters entered a museum and walked away with several thousand objects), set about securing the collections in the country's 40 museums.
Smaller objects went into secure vaults; others, too large to move, were garrisoned off. Some archaeological sites, such as the ancient settlement of Palmyra, stretch for miles, so that there was little more officials could do than lock the gates, knowing full well they could be quickly blasted open.
At first officials were optimistic that the rebels could be persuaded to preserve the sites -- if only for themselves and their children, since they were Syrians. And initially they did. "But now Syria is divided in two: Everyone is for or against the government," said a Syrian official involved in preserving antiquities.
"One always wants to say that archaeology does not take a political position, but by 2012 we no longer had control of the sites." Moreover, as fighters aligned with Al Qaeda, many of whom were foreigners from outside the country, gained the upper hand, the antiquities officials no longer could get a hearing.
"The local people, they kept their promise to guard the sites but the problem is Al Qaeda," the official said. "They are fanatics; they told the curator of one of the museums, 'You are the keeper of statues that are against religion.' "
Muslims, both Sunni and Shiite, as well as Christians, had deep roots in the country and respected, along with each other's heritage, the country's pagan history from its centuries under the rule of ancient Persia, Greece and Rome.
It had a Jewish community as well and there are wall paintings from synagogues long preserved in the Damascus museum, although few if any Jews still live in Syria.
Whether that sense of a shared and diverse past can be reclaimed in this or the next generation is hard to know, but archaeologists and others believe that if there are no artifacts to show Syrians their shared past, the task will be much harder.
"Objects are not just stones," said Irina Bokova, the head of Unesco. "This is about the identity of the Syrian people, and destroying the identity of people is a big blow to their communities."
By Alissa J Rubin