The plan, in the first instance, covered the operations of eight armies, acting in combination. These were the armies of General von Emmich; General von Kluck; General von Bülow; General von Hausen; Albert, Duke of Wurtemberg; the Crown Prince of Germany; the Crown Prince of Bavaria; and General von Heeringen. Embodying first reserves, they comprised twenty-eight army corps out of the forty-six which Germany, on a war footing, could put immediately into the field.[7]
Having reached the French frontier from near the Belgian coast to Belfort, the eight armies were to have advanced across France in echelon. If you take a row of squares running across a chessboard from corner to corner you have such squares for what is known in military phraseology as echelon formation.
Almost invariably in a military scheme of that character the first body, or "formation" as it is called, of the echelon is reinforced and made stronger than the others, because, while such a line of formations is both supple and strong, it becomes liable to be badly disorganised if the leading body be broken. On the leading body is thrown the main work of initiating the thrust. That leading body, too, must be powerful enough to resist an attack in flank as well as in front.[8]
Advancing on this plan, these armies would present a line exposing, save as regarded the first of them, no flank open to attack. Indeed, the first object of the echelon is to render both a frontal and a flank attack upon it difficult.
Had the plan succeeded as designed, we should have had this position of affairs: the eight armies would have extended across France from Paris to Verdun by the valley of the Marne, the great natural highway running across France due east to the German frontier, and one having both first-rate road and railway facilities. It was hoped that by the time the first and strongest formation of this chain of armies had reached Paris and had fastened round it, the sixth, seventh, and eighth armies would, partly by attacking the fortified French frontier on the east, but chiefly by enveloping it on the west, have gained possession of the frontier defence works.
The main French army must then have been driven westward from the valley of the Marne, across the Aube, brought to a decisive battle in the valley of the Seine, defeated, and, enclosed in a great arc by the German armies extending round from the north and by the east to the south of Paris, have been forced into surrender.
There is a common assumption that the German plan was designed to repeat the manœuvres which in the preceding war led to Sedan, and almost with the same detail. That is rating the intelligence of the German General Staff far too low. They could not but know that the details of one campaign cannot be repeated in another against an opponent, who, aware of the repetition, would be ready in advance against every move.
Naturally, they fostered the notion of an intended repetition. That promoted their real design. The design itself, however, was based not merely on the war of 1870-1, but on the invasion of 1814, which led to the abdication of Napoleon, and the primary idea of it was to have only one main line of advance.
The reason was that if an assailant takes two main lines of advance simultaneously and has to advance along the valleys of rivers converging to a point, as the Oise, the Marne, and the Seine converge towards Paris, his advance may be effectively disputed by a much smaller defending force than if he adopts only one line of advance, provided always, of course, that he can safeguard his flanks and his communications.