The entrance is a wet hole in the earth little bigger than an animal burrow, obscured by thorny brush in a secluded wood in northeastern France. I’m following Jeff Gusky, a photographer and physician from Texas who has explored dozens of underground spaces like this one. Together we slither through the muddy hole into the darkness below. Soon the passage opens up, and we crawl forward on hands and knees. The glow from our headlamps wavers along the dusty chalk walls of the century-old tunnel, which slopes away from us down into the shadows. After a few hundred feet the tunnel ends at a little cubicle hewed out of the chalk, reminiscent of a telephone booth.
Here, shortly after the outbreak of the First World War—which began a hundred years ago this summer—German military engineers would take turns sitting in total silence, listening intently for the slightest sound of enemy tunnelers. Muffled voices or the scraping of shovels meant that a hostile mining team might be only yards away, digging an attack tunnel straight toward you. The danger grew if the digging stopped and you heard the sound of bags or cans being quietly stacked, one on top of another. It signaled that the enemy was laying high explosives at the end of the tunnel. Most nerve-racking of all was the silence that followed. At any moment the charges might detonate and blow you apart or bury you alive. (See how World War I energized mapmaking at National Geographic.)
Nearby, on one of the tunnel walls, our headlamps illuminate graffiti left by the German engineers who manned this listening post. Their inscribed names and regiments are crowned by a motto: “Gott für Kaiser! (God for the Kaiser!).” The pencil marks appear fresh, as if they were written yesterday. In fact, the soft chalk and limestone bedrock of France’s Picardy region was ideal not only for mining operations but also for World War I soldiers to record their presence in penciled signatures, sketches and caricatures, carvings, and even intricate relief sculptures. This underground art is relatively unknown beyond a circle of World War I scholars and enthusiasts, as well as village mayors and landowners, many of whom Gusky has spent years getting to know.