The topographical position of the allied powers is the next factor to be considered. Germany's geographical resources have been touched upon, and to them may be added the fact that, if invaded, she had, at the Rhine, a marvelous line to fall back upon. The first factor to be considered in France is its openness to attack. Thanks to the Vosges and the Argonne, a line of great strength could be established (it was so established and was so held in the teeth of determined attack) from Belfort to Verdun. But north of Verdun the earth-making forces have not been kind to France, in a military sense. From Verdun to the North Sea is, geographically speaking, open country. This is not the place to discuss the availability of forts in open country, it is sufficient to point out that there is no geographical defense. Between the German border and Paris there is no topographical barrier to an invading army. The Germans found this out in the Franco-Prussian War, and it had not been forgotten. CHAPTER XXV ASSEMBLING OF THE GERMAN ARMIES "The German mobilization was the greatest movement of people that the world has ever seen. Nearly four million people had to be transported from every part of the empire to her borders. The manner in which the population is distributed made the task extremely difficult. Berlin, Rhenish Westphalia, Upper Silesia, and Saxony, especially had to send their contingents in every direction, since the eastern provinces are more thinly settled and had to have a stronger guard for the borders immediately. The result was a hurrying to and fro of thousands and hundreds of thousands of soldiers, besides a flood of civilians who had to reach their homes as soon as possible. Countries where the population is more regularly distributed have an easier task than Germany, with its predominating urban population. "The difficulties of the gigantic undertaking were also increased by the necessity for transporting war materials of every sort. In the west are chiefly industrial undertakings, in the east mainly agricultural. Horse raising is mostly confined to the provinces on the North Sea and the Baltic, but chiefly to East Prussia, and this province, the farthest away from France, had to send its best horses to the western border, as did also Schleswig-Holstein and Hanover. Coal for our warships had to go in the other direction. From the Rhenish mines it went to the North Sea, from Upper Silesia to the Baltic. Ammunition and heavy projectiles were transported from the central part of the empire to its borders. And everywhere these operations had to be carried on with haste....