MANOEUVRE WARFARE.--In a War of Manoeuvre the steps taken to obtain security against surprise vary with the situation of the troops. Hostile aircraft flying high from the ground are dealt with by counter-attack by armed aeroplanes, but as aerial fighting requires space for manoeuvre hostile machines flying within 3,000 feet of the ground must be dealt with by machine gun, Lewis gun, or concentrated rifle fire, except in cases where it is essential to conceal from the enemy that a certain position or locality is occupied, and where the troops are so well hidden as to escape detection unless they open fire. Movement is easily detected by low-flying aeroplanes, and in fair weather troops can be recognised as hostile or friendly by an observer at 500 feet, while movements of formed bodies on a road are visible at 5,000 feet. Troops remaining stationary in shaded places may easily escape observation, and if small bodies in irregular formation lie face downwards they are difficult to detect, even in the open. When a force is in movement, detachments move with it to afford protection in every direction from which interference {101} is possible; and when a force is at rest, detachments with similar duties secure it from disturbance and keep off attack until it can be met or developed without disadvantage. These phases are dealt with under the headings of "THE ADVANCED GUARD," "FLANK ATTACKS AND FLANK GUARDS," "THE REAR GUARD," and "OUTPOSTS." {102} THE ADVANCED GUARD "Fabius, the saviour of Rome, used to say that a commander could not make a more disgraceful excuse than to plead, 'I never expected it.' It is, in truth, a most shameful reason for any soldier to urge. Imagine everything, expect everything."--SENECA, "_De Ira._" Every moving body of troops must be protected by detachments, the force detached to precede the advance being known as an Advanced Guard, and when a body of troops so protected halts, the responsibility for protection during the halts remains with the troops which have been protecting the march until they are relieved, the commander of the Advanced Guard exercising his discretion as to halting at once or moving forward to occupy a position which may be of more tactical advantage.