World War I, which commenced 100 years ago this month, was a bloody war of attrition. Opposing armies fighting on Europe’s Western Front dug into trenches sometimes only yards apart.  Occasional assaults “over the top” to seize territory were often futile, as soldiers were mowed down by  artillery or machine guns.

But not far from the trenches were underground passageways and shelters where some soldiers spent days at a time. Some of these spaces were in long-abandoned quarries, others were tunnels that engineers dug under enemy lines to place explosives. These underground caverns, most of which are on privately owned land in France, had long been forgotten except by a few locals. When Jeff Gusky, a photographer, explorer and emergency room physician in Dallas, first heard about the existence of these spaces, he began asking locals to lead him inside. Carrying his camera gear on his back through tight passageways and down stairwells, Gusky became one of the first to photograph these nearly untouched spaces extensively.

On the centenary of the conflict, Gusky has been sharing the black-and-white images he made in about 100 caverns and tunnels in France. Most of his images document the graffiti and sculptures left by soldiers nearly 100 years ago. His work has been published by National Geographic, National Public Radio, The Dallas Morning News and other publications.

The carvings and drawings he photographed, Gusky says, remind us that the soldiers who lived and died on the battlefields of World War I were more than statistics. “Men from both sides defied the inhuman scale of modern life and declared themselves as human beings, who could think, and feel, and express and create and who remind us today that they were here, and that they once existed as living, breathing human beings.”