Germany, while maintaining sufficient forces on the Russian front, was still able to put in the field for its great offensive against France a more numerous body of troops than would have been believed in France.  This permitted them to maintain in Alsace, in Lorraine, and in Belgian Luxembourg armies as numerous as those which faced them on the French side, and at the same time to mass the major part of their troops on the right so as to pour into the valley of the Oise their chief invading forces.

This explains why the French left, which was exposed to the offensive of the German right, was obliged to make a rapid retreat, permitting the German armies of General von Kluck and General von Buelow to advance with all speed in the direction of Paris.

The French military staff, as soon as they perceived the danger that threatened, proceeded to a new alignment of forces.  As long as this alignment of forces could not be effected the retreat had to continue.  As soon as it was accomplished, as soon as General Joffre had his armies well in hand and the situation of his troops well disposed, he checked the retreat, gave the signal for the offensive, and so followed the great Battle of the Marne.

The German plan consisted, therefore, in delivering the main blow through the medium of the right wing of the German forces, consisting of the army of Von Kluck, the army of Von Buelow, and the army of Von Hausen, which were to march with all speed in the direction of Paris.

What plan had the French staff in mind to oppose to this plan of the Germans?  Its plan aimed at checking and holding the greatest possible number of Germans by a vigorous offensive in Alsace and Lorraine so as to prevent them from joining the three first German armies which threatened Paris.  In support of this offensive of the armies of Alsace and Lorraine, the central French armies attacked in the direction of the Ardennes and Belgian Luxembourg with the object of checking the center of the German armies and then turning toward the west so as to cooperate in the offensive of the French forces which, aided by the British army and the Belgian army, were fighting in Belgium.

The French armies, which are numbered from the right to the left—­that is, from the east to the west—­comprised:  A detachment of the Army of Alsace that was dissolved toward the end of the month of August; the First Army (General Dubail); the Second Army (General de Castelnau); the Third Army (General Ruffey, replaced at the end of August, 1914, by General Sarrail); the Fourth Army (General de Langle de Cary); the Fifth Army (General Lanrezac, replaced in the last days of August, 1914, by General Franche d’Esperey).  At the right of this army was stationed the British army under the command of General French.

To what resolution did General Joffre, come?  On that memorable evening of the 24th, and on that morning of the 25th, two alternatives presented themselves before him.  Should they, rather than permit the enemy to invade the soil of France, make a supreme effort to check the Germans on the frontier?