There are people who, in fancy, already see cavalry replaced in this rôle by an air fleet. Such prophets cannot, however, be treated seriously. The air cruisers will not be designed for all the possibilities of war. In the period of concentration and in fortress warfare they would doubtless be able, even in their present condition, to render excellent service. Whether they can be adapted for use in a war of movement remains to be seen; but, even if they can in time be of more service for war than at present appears to be the case, their capabilities in this direction will always be limited. They can only observe at night under favourable conditions--such things, for example, as large detrainments of troops or bivouacs with fires burning. They are under all circumstances dependent upon the weather. By day the air fleet of the enemy will seek battle with them in order to hinder their reconnaissance. Hostile artillery will be particularly dangerous to them, and will be able, thanks to the developments in modern ordnance, to wage successful war against them. All detachments cannot possibly be supplied with airships, owing to the great cost and enormous apparatus entailed, and their usefulness will therefore only be realised with the larger formations. Finally, one or the other of the air fleets will be driven from the field, or rather from the air, and that side which meets with defeat will be deprived of all means of reconnoitring unless it can rely on its cavalry. So in the most modern war the cavalry remains the principal means of reconnaissance. Its activity may indeed be supplemented by airships, but will never be replaced by them.[1] These circumstances, however, necessitate a new rôle for cavalry. It must drive the hostile cavalry from the field, a cavalry which will do all in its power to secure its own army against intrusion. It will find this cavalry reinforced not only by horse artillery and machine-guns, but also by cyclist battalions, mounted and other infantry, and will therefore have to be prepared, in order to properly carry out its service of exploration, to fight against detachments of all arms. But the same thing will also happen when it seeks to veil the movements of its own army, or to undertake some enterprise against the enemy's communications, or to defend its own against similar hostile raids. Our cavalry thus finds itself face to face with totally new duties of a most real kind, towards the carrying out of which it has no previous experience to help it.