This map is part of a series of 20 animated maps showing the history of The first World War, 1914-1918.
The formation of the Triple Entente created a difficult military problem for Germany: in the event of conflict, it would be caught in a pincer movement‑ Russia in the east and France in the west.
As early as 1905, the German general staff, commanded by General Von Schlieffen, drew up a plan for defeating France, before Russia was able to mobilize its troops fully.
Schlieffen estimated that the Russian armies would require 6 weeks to regroup.
Despite of the numerical superiority of the German army, this gave him a brief window of opportunity for breaking through the system of fortifications established by France along the Lorraine border after the 1870 war.
Schlieffen therefore envisioned going through Belgium, regardless of its neutrality. The German right wing, which had to be as powerful as possible, would enter France through the region of Lille and afterwards double back towards the south, moving to the west of Paris in a gigantic sweeping movement in order to surround the French armies massed in Lorraine.
Once France was beaten, Germany would turn against Russia.
When the war broke out, the strength of the right wing, as originally foreseen by Schlieffen, was reduced to reinforce the German troops in Alsace and on the Russian front.
From the perspective of the French general staff, Belgium was also the place where the conflict would be engaged, but the British ally was opposed to disrespecting for Belgian neutrality. Plan XVII, which had been mapped out several months before the breakout of hostilities, anticipated that the offensive would be launched in the central section of the front: to the east of the Mosel and between Verdun and Metz. In order to have the troops required for this offensive, the length of military service was set at 3 years.
When the war broke out, the additional manpower was not yet operational.