Situated ten miles from the Belgian border and forty miles inland from the Channel, Lille lay close to the path that an invading army would take if it came by way of Flanders. In answer to General Lebas’ plea for its defense, General de Castelnau spread out a map and measured with a ruler the distance from the German border to Lille by way of Belgium. The normal density of troops required for a vigorous offensive, he reminded his caller, was five or six to a meter. If the Germans extended themselves as far west as Lille, De Castelnau pointed out, they would be stretched out two to a meter.
