PROTECTION AGAINST DIRECT OBSERVATION The concealment of observation posts, machine-gun nests, etc., is comparatively simple, being merely an adaptation of the craft of theatrical property-making. Natural features may be selected, in places from which good observation can be obtained, and these must be copied exactly. At night, the real is removed and re placed by the imitation, e.g., trees, sandbags, mile-stones, mounds of earth, chimney-stacks, walls. The copy is a thin outer shell containing a bullet-proof lining in order to give confidence to the occupier. The loopholes, when subject to scrutiny at short range, can be made quite invisible by the use of gauze, which though painted to resemble the exterior of the O.P., remains transparent from the inside. This method should only be adopted when ab solutely necessary, because gauze interferes with vision—es pecially through glasses; in other cases care must be taken to give the loophole an irregular shape.
The following conditions govern the successful employment of such observation posts, particularly in the case of the more elaborate examples such as trees: I. Concealed access is essential.
2. The works connected with installation must, like other works, be concealed from the air.
3. They should not be erected in places that are normally subject to heavy shelling, for the reason that careful observation will be prejudiced and accidental damage will probably reveal the observa tion post to the enemy.
4. Provision must always be made to prevent daylight showing behind the loophole, thus rendering it transparent to the enemy.
5. The comfort and security of the observer must always be studied, otherwise the full value of the observation will never be obtained.
Imitation trees can be designed either to accommodate an observer at a good height above the ground or to conceal a long periscope, the user of which is protected in a strong dug-out. In the former case the observer has a better view but is un comfortably cramped. The periscope is limited in respect of magnification, field of view and clearness of vision, in proportion to its length (see PERISCOPE). On the other hand, advantage may be taken of its length to obtain high command with corn parative security or increased security with low command. Further, with suitable mountings, it can be used as an instrument of precision in conjunction with map and compass. Provision should always be made to give bullet-proof protection to the periscope when in use, and to allow of its being lowered for clean ing and safety when not in use.
The following are examples from the World War. In the dummy attack, series of painted silhouettes made of stout mill board representing the various postures of advancing troops, were mounted in frames, which could be raised or lowered from places of safety, so as to represent the waves of an attack. This was to draw fire off a real attack. Dummy heads made of papier macho were used for location of enemy snipers, the exact position of whom could be gauged by producing the alignment of the holes of exit and entry of the sniper's bullet. Sniper costumes painted and garnished with local material enabled a skilful wearer in numerous cases to attain close proximity to the enemy without detection.
The screening of roads from observation by the enemy is not in the province of camouflage, in that no deception is attempted. It is unnecessary to erect a screen which is completely opaque in order effectively to conceal traffic on a road. A screen consisting of wire netting with two-thirds of the surface covered with inter laced strips of canvas is sufficient—especially if a chequered effect of black and white be adopted. (F. J. C. W.) BIBLIOGRAPHY.-G. H. Addison, The Work of the Royal Engineers Bibliography.-G. H. Addison, The Work of the Royal Engineers in the European War, 1914-1918, vol. viii., Miscellaneous, Sect. iii. (1927) ; S. J. Solomon, Scientific Camouflage 0920).
Camouflage both of large and small ships on various lines, but with the invariable idea of reducing visibility, had been at tempted in the British navy for many years before the World War, but without success. The Board of Admiralty then adopted a partial form of camouflage by painting all vessels a light grey as opposed to the black hulls and light upper works previously in force. It was not until 1917, during the height of the submarine peril, that a practical scheme, having a definite end in view and formulated on scientific lines was put forward and officially adopted by the British authorities. It was called for distinction's sake in official documents "dazzle painting"; it embodied entirely new ideas on sea camouflage and was rescued from the early decease which had, in turn, been the fate of each of its predeces sors by the fact that its originator was able to supply in large numbers designs to scale, each of which bore out a central idea.
Object.—The sole object of dazzle painting was so to distort the normal appearance of a vessel that her actual course became a matter of doubt in the mind of a submarine officer, the estima tion of a vessel's true course being the prime factor required to ensure a successful attack.
Application.—Dazzle painting was intended primarily for application to merchant ships. These vessels were in far greater need of protection than warships owing to their slow speed and vulnerability and also to the fact that the enemy was making a concerted attack on England's supplies of food and materials essential to the conduct of the World War. A certain num ber of war vessels were, however, dazzle painted. These were chiefly ships engaged on convoy work, although a certain num ber detailed for special duties such as mine-laying and patrol service valued this special form of protection. At first sight it would appear impossible to treat a vessel with paint in such a way that an experienced seaman could be deceived as to her actual course, but dazzle-painted ships proved that this could be done. Juxtaposition of violently contrasted colours, black and white predominating, combined in accordance with the laws of perspec tive, could make it extremely difficult to judge the accurate in clination of a vessel even at a short distance.
Coloration.—In the early stages of dazzle painting, a large range of colours was employed to achieve the end in view. Ex perience showed that this could be attained by a much smaller number, and towards the end of the War, the principal colours in use were black, white and blue, these being employed in varying intensity. A factor which led to the simplification of the colours used was the knowledge that the German naval authorities had introduced the use of colour screens in their submarine periscopes with a view to reducing the camouflaged ship to a silhouette, and so neutralizing the effect of the colours used. These screens, how ever, had no effect whatever on a design depending solely on black, white and blue for its contrast. Shortly after its adoption by the Admiralty, dazzle painting was ordered under the De fence of the Realm Act and the whole merchant service was ordered to be painted. Numbers of war vessels operating with merchant ships were also painted : these comprised chiefly convoy cruisers, sloops and destroyers. The loth Cruiser Squadron, en gaged in blockade duties, was also painted. These vessels were specially liable to attack, being at sea for long periods and con stantly under slow speed or altogether stopped.
On the introduction of the scheme a considerable volume of maritime opinion was directed against it from lack of a proper grasp of its objects, and because it appeared to render a vessel more conspicuous than it was when painted grey. In point of fact, at the date of the submission of the scheme the proposer, who was on patrol duty in the Channel, had noted that all transports were painted a dead black from water-line to truck. The opposition, however, rapidly disappeared as soon as the objects of the scheme were thoroughly grasped, and the rapidly increasing numbers enabled seamen to judge for themselves the difficulties of ac curately estimating the exact courses of dazzle-painted ships met with at sea.
The number of vessels saved by this device can never be definitely ascertained, but its rapid expansion in practice to all Allied merchant shipping showed that the authorities were satisfied that it played a great part. Approximately 4,000 mer chant ships were painted, and upwards of 400 war vessels, en gaged principally in convoy and patrol duties, were also painted. The total cost of painting amounted to some £2,500,000.