Hence it is absolutely necessary that the two systems should be kept separate one from the other, and that each patrol should know clearly and distinctly for which of the two purposes it is specifically intended. Only then can the troops in rear rely on being kept thoroughly informed, and at the same time secure from the possible attempts of the enemy. The more clear and precise the mission, the more can the patrols be relied on to execute it; but this, of course, does not exclude the necessity for them to keep their eyes open for other things, and to report all they may notice. Such a systematic arrangement brings other advantages in its train. It effects a marked economy of one's available forces, for being certain that every mission will be settled by a special party detailed for that purpose, it ceases to be necessary to keep on despatching fresh patrols again and again in the same direction, a practice most detrimental to the troops, which is constantly followed in peace-time; and it can never happen that a body is surprised by the enemy because its scouts are absent reconnoitring, or that it fails to receive information because its patrols are busy with security. If, therefore, all patrols thus naturally fall into one of these two groups--reconnoitring and security patrols--there is still another line of distinction to be observed between these patrols themselves, arising from the nature of the tasks which the circumstances impose upon them. It is impossible to lay down any distinct rules in this matter--for War will always present new and changing problems--but broadly two points of view must be kept in sight, which require fundamentally different treatment, and are conditioned by our distance from the enemy. If the opposing forces are still engaged in preliminary approaches one to the other, and separated by wide stretches of country, the procedure will be altogether distinct from that to be adopted when the outposts mutually confront one another. Between the two extremes there are innumerable intermediate degrees, to which one's conduct must be adapted without losing sight of the guiding points involved. Let us take first the period of approach, and consider the reconnoitring problem from this aspect, taking into consideration the broad requirements of modern War. It will be apparent at once that there is here a double purpose to be fulfilled--viz., to ascertain the whereabouts and direction of movement of the elements of the enemy's main fighting force, the primary object of all reconnaissance; and, secondly, to find the enemy's preceding Cavalry screen, whose purpose it is, on the one hand, to prevent our object, and, on the other hand, to conceal their own main body. This cavalry we shall have to defeat, but we cannot afford to await this event, but must initiate our own reconnaissance before the decision, and endeavour to carry this through, even if the latter prove unfavourable to us.