In the west of Belgium, near the French border, the A19 motorway ends in a four-lane, unfinished overpass. There’s no mountain here, no ocean, no city center. Nothing to explain why the heavy machinery stopped paving through the farms, and the traffic gets diverted to surface streets.

What stopped the Belgian government from paving over this landscape in the early 2000s was the insight that this land contained evidence that might reveal what it was like to live through one of humanity’s greatest horrors. During World War I, this stretch of pastoral landscape, which the generals (and now historians) called the Ypres Salient, was one of the most heavily trenched, mined, mortared, bombed, gassed, pillaged, burned, and bullet-riddled places along the Western Front.

For the archaeologists charged with recovering this landscape’s memories, digging into the past with a vast shovel-and-pickaxe party was out of the question. Not only is the Ypres Salient huge, its scars are so dense they practically form a contiguous strata in the soil. “And, this is an area where people live and plow,” says Birger Stichelbaut, an archaeologist at both Ghent University and the In Flanders Fields Museum. “Our goal was not to turn it into a World War I Disneyland.” They needed non-invasive ways to survey the landscape, identify important sites from the war, and plan for the best way to preserve or protect the artifacts therein.

So, like the armies of Europe a century earlier, they took to the field with the latest tech they could muster: lidar, aerial photography, and geophysical sensors. Their efforts, along with the stories and artifacts those efforts produced, are now featured in an exhibit at the In Flanders Fields Museum (through September) and an accompanying book, both titled Traces of War.

Amateurs and hobbyists had been digging up bullet casings, bones, and bunker material for decades. But the field of professional archaeology had never taken World War I seriously—it happened too recently and left a surfeit of historical evidence. That changed in the early 2000s, when the Belgian government planned to complete the long-delayed extension of the A19, connecting the city of Wieltje to a small town called Steenstraete, and then onward to the coast. However, the Belgian minister in charge of archaeological heritage recognized that meant cutting through what had once been one of the liveliest sections of the Western Front. This slice of the Ypres Salient hosted three major battles, including the one where German forces first used poison gas against the Allies.

So, the politician tasked archaeologists to scout the motorway’s planned route. What they came back with was staggering—trenches, artifacts, bodies. The government canceled the construction project and effectively declared the landscape to be a single, sprawling archaeological site. In the 2009 book Contested Objects: Material Memories of the Great War, Marc Devilde and Nicholas J. Saunders note the significance for the field:

"It is difficult to overestimate the significance of this political intervention, or its consequences for the archaeology of the war … After some 85 years of amateur ad hoc digging and land clearance—and in the space of just over 12 months—a modern scientific archaeology of the Great War had arrived in a legally constituted and academically acceptable form."

Their most valuable resources were aerial surveillance photographs taken during the war. Thousands of these images, taken by both sides, survive. By comparing them to historical documents and modern aerial photography, Stichelbaut and his colleagues could identify areas of interest—a skirmish here, a sortie there. They found miles of forgotten trench lines, identified overgrown moonscapes of bombed out craters, and discovered evidence of supply lines, training grounds, and other key logistical points of interest.