The violation of Belgian neutrality and the passage of the German armies through Belgium had been foreseen by the French General Staff, but opinions differed in regard to the breadth of the turning movement likely to be made by the German right wing in crossing Belgian territory. Among French experts some were of opinion that the Germans would confine themselves to the right bank of the Meuse, while others thought that they would cross the Meuse, and make a much vaster turning movement, thus descending on France in a direction due north and south. If the violation of Belgian neutrality was no surprise to the French Staff, it was nevertheless hardly expected that the Germans would be able to put in line with such rapidity at the outset all their reserve formations. Each army corps was supported by its reserve corps, which showed itself as quick in mobilization and preparation as the active corps. 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.