With the infantry holding shell holes and craters rather than trench lines, the guns frequently hit their own men. To improve observation, the French regained the initiative in the air by grouping fighter aircraft in squadrons and so overwhelming German reconnaissance efforts. On the ground shell supply was maintained by a light railway, constructed during the battle, and by lorry. By June 12,000 vehicles, one every fourteen seconds, were passing up the road from Bar-le-Duc, ‘la voie sacrée’, as it was dubbed by Maurice Barrès in April.
