After the invention of gunpowder, en trenched camps, such as that lust described, proved of very little service, as they afforded no protection against projectiles shot from long ranges, and it became necessary to keep the mass of the army not actually engaged at such a distance in the rear of the fighting line as to be beyond the reach of the most powerful guns of the enemy. In the European War ranges as high as 18 miles were attained, and in a few instances 20 miles was recorded for a few shots from each new gun. The camp, in the old sense, therefore, has lost its former sigw.. cance, and has become little more than a depot of temporary lodgment of reserves, the fighting line and its immediate supports being protected underground in dugouts and bombproof con structions.
With the advent of the fighting aeroplane a new danger has to be met. These machines may rise behind the enemy lines to a height where they are no longer visible, and travel many miles to the rear of an opponent's fighting line and drop high explosives upon a camp which is safe from gunfire. In these conditions the camp must be so disguised by the art of camouflage (q.v.) as to be indistinguishable from the adjacent country when viewed from above by the aviator. The camp defenses, then become reduced to two: (1) Against spies; and (2) against aircraft. For the latter, quick-fir ing guns which may be pointed upward at a high angle, are mounted on automobile trucks, and stationed at outlying points surrounding the camp. It has recently become common to form camps in time of peace for the sake of disciplining the soldiers to a camp life, and exercising them in the evolutions and manmu vres of actual warfare. These are called camps of instruction, of which examples are seen in the United States, where the organizations of the National Guard in the different States are accustomed to annual encampments for these purposes; also in the camp for British troops at Aldershot, and temporary camps throughout Great Britain for the training of the militia and volunteers, and in the like customs and estab lishments of other countries. Such camps are
generally of a permanent type, with substantial buildings and arranged to provide many more of the comforts of life than is usual with camps in the field.
In the United States army the duty of select ing the site and laying out the camp devolves upon the engineer corps. This section of the work of the engineers is termed technically 'castrametation." The practice followed re quires that the site shall be on slightly sloping ground easily drained, and with a sunny expo sure. The surface should be well covered with short grass, and the subsoil should be sandy or gravelly. For a summer camp a high and breezy spot is selected: for a winter camp a site with a southern exposure, and a windbreak of woods toward die north. The water supply should be pure, abundant and reasonably ac cessible. Good roads should approach the camp site from several directions. Fuel; for age, pasture and supplies should be available near by. The streets of the camp are ditched on both sides, and each tent is surrounded with a shallow trench. The streets are swept daily, and no refuse is permitted to lie between the tents. As a protection against epidemics, the camp is moved to a new site every two or three weeks: The United States soldier car ries as a part of his pack a half of a epup>u tent, which buttoned to the half carried by another soldier forms a shelter for 'the two men. When set up it covers a ground area of six feet in length and four feet in width, and is three feet high at the peak. A regiment of 2,200 men requires an area of close to 30 acres, equivalent to a plot of ground about 1,100 feet square. For the permanent camp of instruc tion there is required also a considerable area for drills, parades and manoeuvres. This need not be directly adjacent, but should be conveniently near. See ARMY ORGANIZA rtorr. Consult Moss, J. A., Manual of Military Training> (Menasha, Wis., 1915) ; and Training Officers' Manual> (Menasha, Wis., 1911).