These trenches, both with ourselves and with our enemies, and both in West and East, assumed more and more the character of fortifications, fitted with quickly manufactured wire entanglements such as only modern industry could have been equal to supplying in such enormous quantities. This fact, taken together with the astonishing successes which our heaviest high-angle-fire artillery and also the motor-impelled Austro-Hungarian howitzers achieved against the Belgian and later against the Russian fortresses, has given rise to the idea that in future fortified trenches will take the place of fortresses. In any case it is certain that the old-fashioned fortresses are worthless, and, moreover, that the earlier notion, handed down from the Middle Ages, that positions had to be secured by means of fortresses, must finally be discarded. It has long been among the things which have been outgrown. As early as 1809 Napoleon wrote[4]: "Fortresses like cannon are only weapons, which cannot of themselves fulfil their purpose; they must be properly manipulated and applied"; and in 1806 he said[5] that in the construction of fortresses the same principles were applicable as in the disposition of troops. Fortresses are intended to assist operations, and since the course of the latter can never be foreseen with absolute certainty, it might seem to be the best plan to construct them during the war wherever they are required. That, however, would be going too far. It will not be possible to dispense with certain previously prepared fortified points at places where only defensive tactics can be employed. The fortifications on the French eastern frontier, above all Verdun and the fortified Moselle front, have demonstrated how valuable these may be. When the insufficiently-manned and widely-separated fortifications of the French eastern frontier in 1814 were described by those who opposed the notion of an invasion of France by the allies as "the impregnable front of France," this was a very great exaggeration. A century later, however, it became an actual fact. Even the powerful effectiveness of our heavy and heaviest artillery did not avail at Verdun to enable us to take the works everywhere by storm in the further course of the attack, a proof that skilfully constructed sunk fortifications, when they are favoured by the character of the ground, now as ever may be of great value.