Perhaps the most striking lesson of the war, and the one which is already conclusively taught by its progress, is the fact that modern permanent works, as we have hitherto known them at least, are dominated by modern siege artillery, and in particular by the mobile large howitzer using the last form of high explosive. It is here important to give the plain facts upon a matter which has from its suddenness and dramatic character given birth to a good many lessons. Modern fortification has gone down after a very short resistance to howitzer fire, throughout the western field of the campaign. In general, if you can get the big, modern, mobile howitzer up to striking distance of modern permanent work, it batters that work to pieces within a period which will hardly extend over a week, and may be as short as forty-eight hours. It is not a question of tenacity or courage. The greatest tenacity and the greatest courage can do nothing with a work that has been reduced to ruins, and in which there is no emplacement for a gun. So much is quite certain. But we must not run away with the idea either that this is the end of fortification for the future; temporary mobile batteries established _outside_ the old permanent works will shield a garrison for an indefinite time. Nor is it true that the Germans have in this field any particular advantage save over the Russians, who are weak in their heavy artillery and have limited powers of increasing it. It will be discovered as the war proceeds that the Western armies are here in the same boat with the Germans. It is true that the Germans have a larger howitzer than the French and the English. They have a few 420 millimetre howitzers, that is, guns of a calibre between 16 and 17 inches. But this gun is almost too large to use. What has done the work everywhere is the 11-inch howitzer, and a gun of much the same size is in possession of the French. Only hitherto the siege work has fallen to the German invaders. When and if the _rôles_ are reversed, German permanent work will be just as vulnerable to French howitzer fire. And as for the abolition of fortification in future we need not look for that. It is probable that the system of large, permanent enclosed works will give way to a system of narrow, prepared, parallel trenches connected by covered ways, which, by offering too small a target for accurate fire from a distance, and by being doubled and redoubled one behind the other, will be able to hold out far longer than the larger works which bore the brunt of the present war. But that the defensive will devise some means of meeting the new and unexpected powers of the offensive we may be certain, upon the analogy of all past warfare.