During the night, when it is not possible to occupy advanced areas, the divisional cavalry should try to assist the screen by being so disposed that detached posts will lie on the main road in advance of the infantry outposts and at crossroads and defiles, with a view to capturing the enemy's patrols. The erection of temporary obstacles, particularly of wire, will considerably assist this action. In friendly country the inhabitants will be able to co-operate in this, and, by judicious conduct and the procuring of timely and sufficient intelligence, may be of great use to the force. In erecting such obstacles it must always be remembered that our own advanced patrols should be warned of them, or that by some kind of prearranged mark upon the road they should be made aware of their presence when returning with reports through their own line. It scarcely needs to be emphasised that such measures should be made use of by the army cavalry as well as by the divisional cavalry, in order to increase their own safety at night. IV. RAIDS The idea of the raid has been taken from the American War of Secession. Our new Regulations designate such undertakings as "Streifzüge" (527),[10] and do not appear to attach overmuch importance to them. Their use is only advocated if a superfluity of cavalry is at hand. They should not, it is said, distract the cavalry from their own duties or from co-operating in the battle (395).[11] Whether one agrees with this estimation of the value of such enterprises naturally depends upon the view taken of the co-operation of cavalry in the battle and the general conception of the conditions of modern war. It appears to me that the importance of such undertakings has increased in the same measure as the value of cavalry on the main battlefield has diminished. The great size of modern armies renders it, generally speaking, impossible for them to live on the country. A modern army marching once through the richest country will nowadays almost completely exhaust its resources, and yet the supplies carried will scarcely suffice to feed the columns during a protracted movement. Armies are far more dependent than formerly on the supplies from the rear--more, indeed, than in the time of Frederick the Great. In those days, if the bread-wagons ran short, it was possible to fill up from the country. The armies were never so great that this became impossible. The cavalry, indeed, devoted most of its time to foraging, and the soldier frequently bought his supplies, all except his bread, on the spot.