These troops must be fortified if at all possible. The fortress garrisons are still the source of reserves from which new corps can be formed. The Landsturm in southern Germany can also be deployed to protect the territory left of the Rhine and to cordon off Belfort, etc. A new army must be created and given the assignment to advance on the Mosel between Belfort and Nancy, while the five reserve corps in the left wing and the two Landwehr brigades close off Verdun and attack the Côtes Lorraines.
If, during deployment, the French learn that we are gathering both on the Lower Rhine and the Dutch and Belgian borders, they will not doubt for a moment that the Germans plan to advance on Paris, and they will be wary of advancing to the area between Strasbourg and Metz with either all their forces or their main units. They will also be wary of invading Germany across the Upper Rhine with all their troops. That would amount to ordering the garrison out of the fortress just when the siege is starting. If, despite everything, they do one or the other, it will be welcome to the Germans as it will only make their task easier. It would be most advantageous for us if the French were to invade southern Germany through Switzerland. This would bring us an ally whom we need very badly, one who could engage part of the enemy forces.
In all these scenarios, the Germans would be well advised to alter their operational plan as little as possible. The Lower Mosel must be secured between Trier and Koblenz, and the stretch between the Mosel and the Meuse near Diedenhofen must be closed off. The German army will try to reach the Koblenz-La Fère line with reserves in its right wing. The right bank of the Rhine from Koblenz upward will be occupied from the rear, and the attack will be made with the right wing.
[If the French cross the Upper Rhine, they will meet resistance in the Black Forest. The troops that are moved up from the rear will be assembled on the Main and the Iller.]
If they persist with these operations, the Germans can be sure that the French will quickly turn around, not north but south of Metz, heading in the direction of the greatest danger. It is therefore essential for the German right wing to be as strong as possible, for it is here that the decisive battle can be expected.
Source: Alfred Count von Schlieffen, “The Schlieffen Plan” (1905), reprinted in Gerhard Ritter, Der Schlieffenplan: Kritik eines Mythos [The Schlieffen Plan: Analysis of a Myth]. Munich, 1956, pp. 145-60.
Translation: Adam Blauhut