On the fields that have been smoothed out again, like those surrounding the Devonshires’ cemetery, some of the tractors have armor plating beneath the driver’s seat, because harvesting machinery cannot distinguish between potatoes, sugar beets, and live shells. More than 700 million artillery and mortar rounds were fired on the Western Front between 1914 and 1918, of which an estimated 15 percent failed to explode. Every year these leftover shells kill people—36 in 1991 alone, for instance, when France excavated the track bed for a new high-speed rail line.
