General de Langle, holding Vitry-le-François, barred the approaches to that place and to Sommesous.
General Serrail, with the French army operating in the Argonne, held Revigny. His line extended north-east across the Argonne to Verdun, and was linked up with the positions held by the French army base on that fortress.
General Pau held the line on the east of the fortified frontier.
Some observations on these dispositions of the Allies will elucidate their tactical intention.
The position of the Allied armies formed a great bow, with the western end of it bent sharply inwards.
The weight of the Allied forces was massed round that western bend against the now exposed flank of von Kluck's army. Here lay the most vulnerable point of the German line.
The tactical scheme of the Allied Commander-in-Chief was simple—a great military merit. He aimed first at defeating the German right led by Generals von Kluck and von Bülow. Having by that uncovered the flank of General von Hausen's army, his intention was to attack it also in both front and flank and defeat it. The same tactic was to be repeated with each of the other German armies in succession.
For that purpose the allied armies were not posted directly on the front of the German armies, but between them. Consequently the left of one German army and the right of another was attacked by the same French army. In that way two German Generals would have to resist an attack directed by one French General, and every German General would have to resist two independent French attacks. Hence, too, if a German army was forced back the French could at once double round the flank of the German army next in the line if that army was still standing its ground.
Choice of the battle ground and command of the roads leading to it ensured that this would happen. As a fact, it did.
Finally, all the way behind the French line ran the great road leading across the plateaux from Paris to the fortified frontier. This, with railway communication, gave the needed facilities for the movement of reserves and the transport of munitions and food supplies.