The 75-kilometre stretch of country road between Bar-le-Duc and Verdun was the only supply line into the besieged town during the Battle of Verdun. Trucks ran along it bumper-to-bumper, day and night, for ten months — at the height of the battle, one passed every 14 seconds in each direction. Soldiers nicknamed it the Sacred Way; it was given that name officially in 1923.
It is signposted as the Voie Sacrée Nationale and marked with stone milestones topped with First World War helmets. Driving it slowly today, through quiet Lorraine farmland and forests, is a more thoughtful experience than any single monument. The villages along the route — Souilly (Pétain's headquarters), Erize, Chaumont-sur-Aire — are worth stopping in.