Under Plan XVII, the French peacetime army was to form five field armies of about two million men, with groups of Reserve divisions attached to each army and a group of reserve divisions on the flanks. The armies were to concentrate opposite the German frontier around Épinal, Nancy and Verdun–Mezières, with an army in reserve around Ste. Ménéhould and Commercy. Since 1871, railway building had given the French General staff sixteen lines to the German frontier against thirteen available to the German army and the French could afford to wait until German intentions were clear. The French deployment was intended to be ready for a German offensive in Lorraine or through Belgium. The French expected that the Germans would use reserve troops but also assumed that a large German army would be mobilised on the border with Russia, leaving the western army with sufficient troops only to advance through Belgium, south of the Meuse and the Sambre rivers. French intelligence had obtained a 1905 map exercise by the German general staff, in which German troops had gone no further north than Namur and assumed that plans to besiege Belgian forts were a defensive measure against the Belgian army.