Part of our weekly "In Focus" series—stepping back, looking closer.

The battered white Corolla rumbles down a rocky road past fields of okra and great earthen mounds topped by the crumbling remains of ancient battlements. Taking a hard right and then a hard left, the old car bounces up onto a small dirt soccer field and jerks to a stop.

"All of this is the tepe," says Abdul Wahid, a neatly dressed farmer in his 40s, pointing at a dirt expanse so pitted it looks like it has been carpet-bombed. He gets out of the car and walks over crumbling humps of dirt, skirting pits left by looters.

"You see that big hole over there," he says, gesturing. "During the civil war, some people were working it and they took out a lot of things." Still, there is more to find, he says.

Abdul Wahid is showing me around the tepe, or hill, across the dirt lane from his compound in Balkh—a city in northern Afghanistan that ancient Arab explorers once called Umm Al-Belaad or "Mother of Cities" for its great antiquity. For decades he and his family have looted this site inside the much larger urban complex of ancient Balkh, believed to have been a spiritual center of Zoroastrianism, and wealthy enough to have been deemed worthy of sacking by both Genghis Khan and Tamerlane. Indeed, over the millennia, Afghanistan has been a crossroads of both cultures and armies, resulting in chaos and opportunity.

"The civil war was a good time for us because we could dig even during the day," says Abdul Wahid. "In 1991 I found a big platter with about five or six other guys from the village. There were pictures of animals on it. We sold it for $600 and divided the money."

Walking around, broken pottery clinks under our shoes. Here and there turquoise potsherds blaze in the dust, haphazardly uncovered by rain or the hooves of goats. "The history here is important to the people, but they are very poor. For this reason they sell these things," he says.

Poverty and War Opened Doors to Looters

Today, though, some safeguards exist, at least around this site. As I wander away, eyes locked to the ground, he warns me, "You cannot walk in that direction. There is a police checkpoint that way. If they see people walking up here looking around, they will call you over and question you."

Abdul Wahid says the arrival of foreign archaeologists and the creation of a police checkpoint to stem illegal digging has changed the situation. "I don't work over here anymore. The people are not happy with them digging here. The only people who are happy are the poor people who are getting a salary excavating the site."

Despite these official efforts to control art theft, the war has been a boon for both looters and smugglers—he first two links in the supply chain that gets artifacts out of the ground and on the way to dealers around the world. Yet, this problem could take a turn for the worse when the majority of foreign military forces withdraw at the end of 2014. Both Afghan and foreign observers worry that the vacuum created once the troops leave could lead to a return to the anarchy of the pre-Taliban days of the civil war and a parallel rise in the vulnerability of cultural heritage.

"We'll just have to wait and see. The worst and the best have not been written in this country yet," says Philippe Marquis, the director of DAFA, the French archaeological delegation in Afghanistan, which is running the dig in Balkh.

"The looting of archaeological sites is first of all an economic problem, then a political one. If people are looting, it is because they want money. So, if the economic situation worsens after the withdrawal, I would say that people will go back to [looting] antiquities," he says.

Priceless Finds in the Fields

After a few more minutes looking around, Abdul Wahid invites me to his neighbor's house. The base of a column serves as the first step into the guestroom. I gingerly put my weight on it, step inside and take off my shoes. Mohammad Hassan, an older farmer, shakes my hand and reaches into a hidden pocket, pulling out a piece of light-blue cloth tied in a tight bundle. Inside the rag is a heavy black plug of stone, a stamp flecked with green. On one side of the stamp two lions are fighting. Lying next to it is a small glass vial. I catch the glint of gold.

Hassan carefully pulls the stopper and drops the contents into my palm. The face of a man peers up at me. With a full beard, he looks much like Hassan, though the face also has a drooping mustache and a band around the forehead. "We put the dirt from a field we were leveling onto a screen and poured water over it. This is what I found. This is the first face we have ever found. Now we know what they looked like."

Another farmer wants to show me a big artifact he has found, so we all head over to a raised earthen platform in the deep shade of a sycamore grove on the edge of a nearby okra field. A group of farmers is waiting for me. One drags a woven sack into the middle of the circle. Unwrapping layer after layer of ragged bags, he reveals a high-relief Kushan statue of a man and woman and servant, draped in robes like those worn by the great Buddhas in Bamyan before they were destroyed by the Taliban in 2001.

"You're the first foreigner to see it," says Gul Agha. "I found it around 15 years ago during the time of the Taliban." He wants $10,000 for it. When I ask how he feels about having such a remarkable piece of history in his hands, he shrugs. "I didn't have any reaction when I found it. When I get the money, then I'll be happy. Now it's just a rock for me," he says.

All of these farmers are keen to part with these pieces of antiquity, and the sooner the better. "If I took the golden head to Mazar-i-Sharif [the nearby provincial capital] and the police found it at one of the checkpoints, they'd arrest me. They'd ask me why I have this thing. We are poor people and if the police find us with this sort of thing, they'll cause problems for us," says Hassan. "Here, it's fine. If it's a small thing, it's fine with the police. But if it's a bigger thing, then we can have a problem, even here. The police don't care about small things." The blind eye—and worse—has allowed the plundering of Afghanistan's cultural heritage on a vast scale.

Industrial-Scale Theft

"There is a common saying in northern Afghanistan that there are four seasons: an opium season, a hashish season, winter, and a fourth season for digging up antiquities," says Marquis, the DAFA chief. "I would say that 99 percent of the archaeological sites in Afghanistan have been looted. But the difference between 30 years ago and today is the extent of the looting and also that people are organized to do the looting, which was not the case before. The quantity, the extent of the looting, it's very difficult to call it industrial, but I would say it is huge, huge quantities," he says.

While no exact figures exist—U.S. and Afghan customs, UNESCO, archaeologists, curators, and experts in the U.S., the U.K., and Afghanistan will offer only rough estimates for the number of artifacts looted and illegally trafficked abroad—the consensus is that Afghanistan is rapidly losing its heritage on a vast scale.

"If we go to the countryside, very large sites and very small sites have been systematically targeted. We have medieval towns, Greek cities, and Bronze Age cemeteries that have been methodically dug over—not just the work of amateurs with a shovel, but hundreds of workmen being managed and working for the trade," says St. John Simpson, author of Afghanistan: A Cultural History and senior curator for the pre-Islamic collections from Iran and Arabia at the British Museum.

Although the scale of looting in Afghanistan is unique, the plundering of war zones is not. From the wars in Iraq to the bitter civil war in Syria, down to the sacking of Rome by the Vandals, the looting of antiquities and valuables has gone hand-in-hand with warfare. "We generally see industrial-scale looting begin to occur when there is a withdrawal of government stability, when there is a period of lawlessness," says Brian Daniels, the director of research and programs at the University of Pennsylvania's Penn Cultural Heritage Center and a specialist in cultural heritage policy.

If the industrial level of digging is not slowed or halted before the pullout at the end of next year, when the Afghan government will increasingly be on its own, it could prove catastrophic, since Afghanistan's unique history remains largely undocumented. With both Alexander the Great and Buddhism figuring prominently before the coming of Islam, "Afghanistan was the easternmost extent of Western culture and the westernmost extent of Eastern culture," says Sara Noshadi, a UNESCO program officer in Kabul.