Now let us glance at the tactical scheme on the German side.
The fact that General von Kluck had left two out of the five corps forming his army on the Ourcq, and was covering his movement to the south of the Marne with his cavalry, proves that he did not, as was supposed, intend to lose contact with Paris. His scheme was to establish an echelon of troops from the Ourcq to La Ferté Gaucher on the great eastern road, believing that to be meanwhile a quite sufficient defence.
With the rest of his force he was to join with von Bülow and von Hausen in smashing through the French position at Sezanne. Against that position there was to be the overwhelming concentration of ten army corps.
To assist the stroke against Sezanne there was a concurrent intention to break the French line at Vitry-le-François. The French line between Sezanne and Vitry-le-François would then be swept away.
Assuming the success of these operations, the German forces would be echeloned south-east from the Ourcq across the valley of the Marne and the plateau south of it to Troyes on the Aube. The Germans would then be in a position to attack in flank the French retreating from the frontier, and ready, when these French troops fell back, pursued by the armies of the Crown Princes of Germany and Bavaria and by von Heeringen's army of the Vosges, to join in the great sweep along the valley of the Seine and round to the south of Paris. By this time, remember, the long lines of communication through Belgium would have ceased to be vital.
It was a bold scheme.
There are, however, other factors to be taken into account besides tactical plans.
Not less a surprise than the apparently sudden change in the German movements had been, during the preceding week or more, the seemingly hardly less precipitate falling back of the French upon the Marne. All the world believed that the French were "on the run," and all the world thought they would keep on running. Day by day during that exciting time the inhabitants of the valley of the Marne witnessed column after column of their defenders apparently in full retreat. The marching qualities of the French are, as everybody knows, remarkable. They showed the enemy a clean pair of heels. Few could understand it.
Then came the Germans, hot on the scent, confident that the French could never withstand them. From over the highlands by every road they poured into the peaceful Marne valley like a destroying flood. In front of them swept a multitude of fugitives.