What we desire to establish here is, that if in tactics the military force through the mere duration of actual employment suffers a diminution of power, if time, therefore, appears as a factor in the result, this is not the case in Strategy in a material degree. The destructive effects which are also produced upon the forces in Strategy by time, are partly diminished through their mass, partly made good in other ways, and, therefore, in Strategy it cannot be an object to make time an ally on its own account by bringing troops successively into action. We say on “its own account,” for the influence which time, on account of other circumstances which it brings about but which are different from itself can have, indeed must necessarily have, for one of the two parties, is quite another thing, is anything but indifferent or unimportant, and will be the subject of consideration hereafter. The rule which we have been seeking to set forth is, therefore, that all forces which are available and destined for a strategic object should be _simultaneously_ applied to it; and this application will be so much the more complete the more everything is compressed into one act and into one movement. But still there is in Strategy a renewal of effort and a persistent action which, as a chief means towards the ultimate success, is more particularly not to be overlooked, it is the _continual development of new forces_. This is also the subject of another chapter, and we only refer to it here in order to prevent the reader from having something in view of which we have not been speaking. We now turn to a subject very closely connected with our present considerations, which must be settled before full light can be thrown on the whole, we mean the _strategic reserve_. CHAPTER XIII. Strategic Reserve A reserve has two objects which are very distinct from each other, namely, first, the prolongation and renewal of the combat, and secondly, for use in case of unforeseen events. The first object implies the utility of a successive application of forces, and on that account cannot occur in Strategy. Cases in which a corps is sent to succour a point which is supposed to be about to fall are plainly to be placed in the category of the second object, as the resistance which has to be offered here could not have been sufficiently foreseen. But a corps which is destined expressly to prolong the combat, and with that object in view is placed in rear, would be only a corps placed out of reach of fire, but under the command and at the disposition of the General Commanding in the action, and accordingly would be a tactical and not a strategic reserve.