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WAR DEPARTMENT FIELD MANUAL (1944)
FM 5-20
CAMOUFLAGE, BASIC PRINCIPLES

TOC Ch1 Ch2 Ch3 Ch4 Ch5 Ch6

CHAPTER 4

HIDING AND BLENDING

SECTION 1. USE OF NATURAL MATERIALS

10. GENERAL. -- Natural camouflage materials match local colors and textures and, when correctly used, are proof against both direct and photographic observation. Their use reduces the quantity of supplies to be carried from rear areas. However, in combat zones they cannot be prepared ahead of time, are not always available in usable types, and foliage wilts after cutting and requires renewal. Foliage of coniferous trees (evergreens) retains its camouflage qualities for considerable periods, but foliage that sheds leaves wilts in a day or less, depending on climate and type of vegetation

11. LIVE VEGETATION. -- Planted rapid-growing weeds, grasses, vines, bushes, and small trees are used extensively to conceal permanent and semipermanent installations. The fastest-growing weeds in the locality are often useful for living camouflage. In some instances relatively large trees are transplanted to furnish concealment, but this method, requiring special equipment and skill, is exceptional. Small trees and bushes can be potted successfully. In barren areas, scrub growth is an excellent supplement to artificial garnishing on nets.

a. Vines -- Vines have approximately the same color and texture from all sides. They grow quickly in a tropical climate and can be trained on wires over permanent installations (fig. 37). They can cover screens, serve as garnishing, and break up an even tone. Grown on skeleton forms, they can simulate trees.

FIGURE 37. (78K) -- Vines make a concealing cover for this seacoast installation

b. Grasses. -- (1) Controlled mowing. -- The controlled mowing of grasses is a technique sometimes included in camouflage plans of airdromes and rear-area installations. Controlled mowing means mowing one section or area all at the same height and in the same direction, with adjacent areas at different heights and directions; this results in what appears to be fields with different crops (fig. 38).

FIGURE 38. (57K) -- Grass landing field where directional mowing simulates agricultural patterns. Edges of fields are outlined by painted boundaries .

(2) Toning. -- Grass may be toned by spraying with chemicals such as iron sulphate, sodium arsenite, or ammonium thiocyanate. The process must be carefully controlled. The vegetation will be discolored, but the damage will be slight and temporary. After a period of a few days to a few weeks, depending on the rates of application employed, the grass resumes normal growth. In the case of ammonium thiocyanate, the grass turns a rich deep green following the burn, because of the nitrogen supplied by the spray. Asphalt emulsions and tannin dye also are suitable for toning. Waste oil may be used, but it prevents growth of grass for several months after application.

FIGURE 39. (69K) -- If time permits, place sod or brush over new spoil. Sod must be watered to keep it alive.

FIGURE 40. (72K) -- Cut foliage must always be placed as it appears in its natural growing state.

FIGURE 41 (73K) (1). -- Chicken wire supports this cut vegetation in its natural upright position. Smooth-strand wire anchors butts. (2).-Alternate method employs two separated layers of chicken wire.

12. CUT VEGETATION. -- a. When freshly cut vegetation is used as garnish or screening, it must be replaced with fresh-cut materials, or painted, as soon as it has wilted sufficiently to change color or texture. If vegetation is not maintained it is ineffective. Thorn bushes, cacti, trees, and other varieties of desert growth retain growing characteristics for long periods after being cut. Evergreens in snow-covered terrain are especially lasting.

b. Arrangement of cut foliage is important. Upper sides of leaves are dark and waxy; under sides are lighter. In camouflage, therefore, cut foliage must be placed as it appears in its natural growing state -- top side of leaves up and tips of branches toward the outside of the installation. Cut foliage must be matched to existing foliage. For instance, foliage from trees that shed leaves must not be used in an area where only evergreens are growing. Choose foliage with leaves that feel leathery and tough. Branches grow in irregular bunches and, when used for camouflage, must be placed in the same way. When branches are placed to break up the regular, straight lines of an object, use only enough branches to accomplish this purpose; it is not necessary to cover the object completely.

c. Methods of supporting natural materials are shown in figure 41. Chicken wire and small smooth-strand wire are commonly used for this purpose.

FIGURE 42. (75K)

d. Cut green vegetation may be sprayed with bituminous emulsion in a matching color to prolong the time it can be used (fig. 42) .

13. DEBRIS. -- Debris furnishes valuable means of concealment. Frequently it may be used just as it is found. Positions concealed by debris require little maintenance. Debris also makes excellent decoys. Planes beyond repair, for instance, may be placed in partly concealed positions and, with the addition of simulated activity nearby, may lead the enemy to waste ammunition. Rusty tin cans cut into strips and combined with cloth can be used to garnish wire nets (fig. 43).

FIGURE 43. (54K) -- Sides of tin cans are slit at intervals. Pieces of cloth are crimped into ends of resulting strips.

FIGURE 44. (269K) -- Mud used to tone down bright surfaces on bayonet.

14. EARTHS. -- Earth, sand, and gravel are used to change or add color, provide coarse texture, simulate cleared spots or blast marks, and create forms and shadows.

a. Earth, in mud form, provides good material for tonedown of bright surfaces (fig. 44). The combat soldier, using mud, can quickly tone down his shoes, leggings, and vehicle. Artificial rocks may be colored and textured effectively with mud.

b. Sand adhering to paint or oil provides means for toning down vehicles in the desert. In the desert, dispersed supply points under tarpaulins, if made low and irregular in outline, can be hidden effectively by covering them with sand.

c. Gravel is used to provide texture on roads, roofs, and other flat surfaces. It is not altogether satisfactory on runways because, if dislodged from the adhesive, propeller blasts cause particles to fly into and damage airplane parts.

SECTION II. USE OF ARTIFICIAL MATERIALS

15. ISSUED MATERIALS. -- Camouflage materials issued include shrimp nets, twine nets, chicken-wire netting, cloth garnishing, steel and glass-wool garnishing, smooth soft steel or iron wire, rope, wood and steel stakes and posts. For complete details see FM 5-20H and Engineer Supply Catalog.

16. PURPOSE OF CAMOUFLAGE NETS. -- A garnished camouflage net, either twine or wire mesh, is supported on a wire frame to make a flat-top. Erected over an object, it conceals the object by breaking up its form and shadow. The garnishing in the net blends with the surrounding so the net itself cannot be seen. Twine camouflage

FIGURE 45 (123K) -- Net with standard arrangement of garnishing patterns.

FIGURE 46. (102K) -- Hanging net vertically facilitates garnishing.

nets are also used as drapes for the same purpose. A drape is supported above an object by poles.

17. GARNISHING FOR FLAT-TOPS. -- a. Garnishing material is woven or tied to nets and netting. The standard arrangement of patterns can be used effectively e!wherever there is a naturally rough ground texture. For other types of terrain, special arrangements should be used. For pattern arrangement on drapes, see paragraph 20.

b. The standard arrangement is irregular in outline (fig. 45). Approximately 80% of the center area of the net is covered. Toward the edges, the garnishing is thinned to approximately 10% coverage. For estimating purposes, total area of garnishing is about 55% of the area of the net. Thinning the amount of garnishing at the edges is important, because it serves to blend the screen with its surroundings and prevent conspicuous straight-edged shadows. Particular care must be taken to keep thick garnishing away from the corners.

FIGURE 47 (1). (49K) -- Greek-key pattern for strip garnishing. Pattern is woven parallel to edges of net.

FIGURE 47 (2). (47K) -- U pattern for strip garnishing. At edges of pattern arrangement, open ends of U-form are made to point towards nearest edge of net.

18. APPLICATION OF GARNISHING. -- Nets are easily garnished when hanging vertically (fig. 46). The most difficult position is when they are attached to an overhead frame. Tests have shown that there is little difference in effectiveness between the many garnishing patterns. Two patterns, known as the Greek-key pattern and the U pattern, have certain advantages. They save time, are easily applied, and the basic design is easy to control; together, they achieve the desired irregularity and blending effect.

a. Greek-key pattern (Fig. 47 (1)). -- Strips of garnishing are woven parallel to the sides of the net in a "squared spiral" or fretwork design.

b. U pattern (Fig. 47 (2). -- Each strip of garnishing is woven in U-shape. The pattern is made irregular. Near the edges of the net, the strips are woven so that both ends, still following the U-form, point toward the nearest edge of the net.

c. Special patterns. -- Properly colored straight-line garnishing (fig. 48) is particularly useful in barren terrain and areas of smooth uniform texture. In broken, mottled terrain, patch garnishing may be used to match the terrain pattern. Patch garnishing is illustrated in figure 49. Bow-tie garnishing (fig. 50) is useful in matching thick, leafy texture.

FIGURES 48. (323K) -- In correct color proportions, straight line garnishing disguises a headquarters tent in open terrain.

49. -- Patch garnishing. Bunching material deepens texture.

50. -- Bowtie garnished drape does a complete job of matching thick leafy background.

19. MATERIAL AND LABOR REQUIREMENTS- FLAT-TOPS. -- The following table gives the approximate amount of materials and man-hours required to garnish the different-sized twine nets when they are to be used as flat-tops.

20. GARNISHING FOR DRAPES. -- When twine nets are garnished to be used as drapes, garnishing is carried completely out to the edge of the net and thinned to approximately 50 percent of the outer area covered, so that the total covered area of the net is about 65 percent, instead of 55 percent. For this use, the table above should be revised by adding one-sixth or 17 percent to the materials and man-hours required.

21. COLOR PERCENTAGES FOR GARNISHING. -- When artificial materials are used, color patterns may be sprayed on to match the surroundings. Precolored cloth can be selected to match. The following table gives the color percentages necessary in garnishing for various kinds of terrain.

SECTION III. DRAPES, FLAT-TOPS, AND SCREENS

22. DRAPES. -- Standard drapes are either shrimp nets, ungarnished, or twine nets, garnished. Drapes are commonly used over vehicles, planes, structures, and equipment which must be camouflaged quickly with little labor. To be effective, drapes must be associated with natural ground patterns.

a. Application of drapes. -- The drape is held away from the object by supports (fig. 51) so it does not reveal the outline of the object, but presents an irregular form. It is drawn out and staked to the ground; or the edges may be thrown over low bushes, or held down by weights. Eight to twelve stakes are required for each large net. Four to six are sufficient for 15- by 15-foot and 29- by 29-foot nets. If available, some natural materials from the immediate vicinity are added to give improved blending qualities to the drape.

b. Twine nets used as drapes. -- Twine nets should be pregarnished with artificial materials to save time at the site.

c. Drapes instead of flat-tops. -- Drapes are used when it is not practicable to erect a flat-top. Drapes are usually successful in concealing an object from direct observation, although it is usually possible to detect their presence on an aerial photograph. In the latter case, however, identity of the object beneath the drape is concealed.

23. FLAT-TOPS. -- A flat-top (fig. 53) is used to conceal a position from overhead and oblique observation. It consists of a twine net (or chicken wire for permanent installations) stretched flat and garnished correctly with natural and artificial materials to blend with the background (see par. 17) . When erected and garnished correctly, flat-tops conceal against all types of aerial observation.

a. Flat-tops must be parallel to the ground (fig. 52). On a hill- side a flat-top follows the slope of the hill. A flat-top covering a large area must have variations in slope to conform to the ground.

b. Normally a flat-top should be at least 2 feet above the surface of the object to be concealed (fig. 54).

FIGURE 51 (95K) -- Drapes must be held above and awayfrom the object by props to make the shape of the installation irregular and to conceal identity of object.

FIGURE 52. (23K) -- Flat-tops must be parallel to the ground.

FIGURE 53. (133K) -- Small flat-top conceals a machine gun from oblique and overhead observation.

c. The area under a flat-top should be matched to its surroundings with sod, leaves, and other natural materials. Concealment is more complete if the object is toned to match its background.

d. Flat-tops must bear wind and snow loads, and large permanent flat-tops should usually be strong enough to support men engaged in repair and maintenance operations. The area to be concealed is wired in, and access paths are run under cover or along natural lines in the terrain to prevent tracks showing.

FIGURE 54. (24K) -- Normally a flat-top should be at least 2 feet above the surface of object concealed.

FIGURE 55. (73K) -- This flat-top is too high and too heavily garnished. It casts a conspicuous shadow.

24. HEIGHT OF FLAT-TOPS. -- The closer to the ground a flat-top can be placed, the more chance it has to escape discovery. A high flat-top may not be disclosed in a single aerial photograph, but under stereoscopic examination it will appear to be floating in the air. Shadows cast by the garnishing of a high flat-top can be seen (fig. 55 ) . For complete concealment flat-tops should be no more than 3 feet above the general height of the vegetation at their edges. If the position does not permit this, the installation is dug in or the flat-top is supplemented by sloped screens (par. 35).

FIGURE 56. (25K) -- Flat-top should extend beyond the concealed object on each side a distance twice the height of the flat-top.

25. PROTECTIVE AREA OF A FLAT-TOP. -- The flat-top should extend past the area to be concealed on each side by a distance equal to twice the height of the flat-top above the ground (fig. 56). This provides an all-around margin to protect from oblique observation and to allow for thinning the garnishing at the edges. Even the most skillfully prepared camouflage flat-top does not conceal the entire area under the net. The higher the flat-top, the smaller the area effectively concealed from oblique observation. The outer area of the net provides little concealment-unless the net is used at ground level. Objects near the edge of the net must be concealed by supplementary cover.

26. TYPES OF FLAT-TOPS. -- a. Flat-top material may be (1) small, standard, T/E twine nets (fig. 58) without organic supports; (2) T/E net sets composed of standard twine nets with standard supports, wire cables, and anchors (fig. 57); or (3) of material from depots-engineer class-IV supplies (fig. 59). Net sets have fixed erection procedures which are described in the supplements to this manual. The following procedures describe general deliberate erection, using T/E equipment supplemented by depot stocks or using depot stocks entirely.

FIGURE 57. (187K) -- Issue net set erected over artillery emplacement.

FIGURE 58. (89K) -- Small flat-top, using issue camouflage twine net.

FIGURE 59. (92K) -- Irregular low flat-top, using chcken wire.

27. PROCEDURE FOR ERECTING 15- BY 15-FOOT FLAT- TOP (fig. 60). -- This flat-top is usually erected close to the ground because it is employed to conceal small weapons such as machine guns and mortars.

a. Supports. -- The supporting framework consists of four posts which form a square 18 feet on a side. Each post is approximately 2 feet long, depending on the height of the flat-top, and 2 or 3 inches in diameter. Twelve stakes are driven, 4 to 6 feet out from the posts, in prolongation of the sides and diagonals of the square. Instead of wooden posts and stakes, standard barbed-wire equipment-medium screw pickets and anchor pickets-may be used to advantage in some soils. The framework supporting the flat-top consists of strands of No. 10 wire, which form the sides and diagonals of the square.

FIGURE 60 (63K) (1). -- Plan of 15- by 15-ft. flat-top. (2).-Wiring diagram.

b. Wiring. -- Two nails are driven into the top of each post. Posts are inclined toward the center while the wire strand is twisted two or three times around a stake, the free end being left long enough to be doubled back and fastened near the top of the post. The wire is brought back over the post between the nails, which act as guides to hold it in place, thence to the opposite post, and down to the bottom of the anchor stake. Two or three turns are taken around the stake, and the free end is left long enough to be fastened near the top of the post. When all wires have been placed, the posts are straightened to tighten the wire, the ends of the wire are tied back near the tops of the posts, and the nails are bent down to prevent the wire from slipping off. Maintenance tightening is accomplished by racking the double guys between posts and stakes.

c. Net. -- The net is then placed on the frame and attached by pieces of No. 16 wire. If the flat-top is to be used for high-angle weapons, a slit embrasure about 6 feet long is provided in the center of one side, as shown in figure 60. This embrasure is closed by a quick-release device, as shown in figure 67. When it is desired to open the net, the lacing is released by a pull on the rope.

28. PROCEDURE FOR ERECTING 29- BY 29-FOOT FLAT- TOP. -- Nets of this size are used for both flat-tops and net sets. If erected as a flat-top, the method used in figure 60 is employed. This method is that used for a 15- by 15-foot flat-top, except that posts are about 3 inches in diameter, an additional post is placed in the middle of each side, with a stake outside it, and two additional wires are used to connect intermediate posts and stakes. When it is necessary

FIGURE 61 (a). (47K) -- Erection of flat-top.

A Materials piled in center of site.

B Two 2-man crews drive stakes vertically. One nail is driven in outer side of each stake near ground.

C Two men hold posts at opposite sides, with tops inclined about 1 foot toward each other.

D One man feeds wire from coil to prevent tangling.

E One man strings wire.

Note. If embrasure is used, it is inserted in edge wire nearest enemy. See figure 62.

to provide an opening for fire on one side, the middle post on that side and on the opposite side, and the wire between them, are omitted. The frame for this flat-top is approximately 33 feet square.

29. PROCEDURE FOR ERECTING 36- BY 44-FOOT FLAT- TOP. -- The recommended way to erect the wire frame for a 36- by 44-foot net requires a detail of one noncommissioned officer and eight men. The 12 posts for the frame are 2- by 4-inch lumber or 3-inch round poles squared at both ends. On soft ground, the lower ends are placed on footings. Two nails are driven into the top of each post and one nail is driven into each side about 8 to 12 inches below the top. Posts are the desired height of the flat-top. Stakes ( 16 required) are the same size as the posts and about 2 feet, 6 inches long. No. 10 wire is used for the wire frame. For erection procedure, see figure 61.

FIGURE 61 (b). (23K) -- Wire is attached to near stake, leaving extra length for double guy, carried over top of near post, over side nail of far post and pulled tight before fastening to far stake.

FIGURE 61 (c). (21K) -- Lower far post and place wire between nails on top of post. Push both posts out to erect position to tighten wire.

FIGURE 61 (d). (19K) -- Posts are anchored in erect position by fastening free ends of wires above side nails.

FIGURE 61 (e). (28K) -- The edge wires are strung hand-tight on the sloping portions of the guy wires and are tightened further by being lifted onto the tops of the posts.

FIGURE 61 (f). (37K) -- The intermediate wires are erected under the first four wires to facilitate tightening.

FIGURE 61 (g). (20K) -- Loose wires are tightened by racking double guys or by driving stakes deeper into ground.

FIGURE 62 (a). (42K) -- If flat-top is used for artillery, embrasure release is inserted in the edge wire neares enemy.

FIGURE 62 (b). (61K) -- Net is unfolded over frame with embrasure opening -- if any -- toward enemy. It is stretched tight and fastened to perimeter wire with pieces of No. 16 wire, about 2 ft. 6 in. long, at 3-ft. intervals. The embrasure is held closed with a 'quick-release" device (fig. 67) so that a pull on the rope will open the entire embrasure.

30. PROCEDURE FOR ERECTING IRREGULARLY SHAPED FLAT-TOP (Fig. 63). -- A frame of this type may be used to support either a garnished net or plain wire netting used as a base for natural materials. Although it requires more material to erect than other flat-tops, it is adaptable to any size or shape of cover. Construction procedure follows:

a. Lay out posts about 12 feet apart in each direction of area to be covered.

b. Drive side nails in outside posts only.

c. Run No. 10 diagonal wires across each line of posts, placing wires between nails on top of posts.

d. Tighten diagonal wires by racking at crossings in centers of squares. This will tighten whole frame.

e. Additional bays may be erected around edges to make outline irregular.

f. After erection, interior posts may be shifted in position to accommodate needs of occupying troops, without loosening frame.

g. Maintenance tightening may be accomplished by racking doubled portions of main wires and intersections of diagonal wires. The nails and wire used in these flat-tops can seldom be used again. All posts and about 50 percent of the stakes can usually be salvaged.

FIGURE 63. (39K) -- Irregularly shaped flat-top.

31. HOLDFASTS. -- In different soil conditions, different types of holdfasts are required. Types used commonly are single stake in firm soils; double and triple stake in loose soils; screw anchor and screw picket in firm soils; log, concrete, and sandbag deadman in sandy and soft soils; and counterbalances can be used, as expedients, in rocky, frozen, or sandy soils (fig. 64).

32. MAINTENANCE OF FLAT-TOPS. -- a. The maintenance of flat-tops is essential. Twine nets shrink approximately 10 percent when wet. In shrinking, they develop sufficient tension to break the threads, pull out tightly driven stakes, or break No. 10 wire. Nets must be loosened during a rain and at night when there is a possibility of dew. This loosening is permissible because enemy observation is handicapped at these times. At all other times nets must be kept tight, because a sagging net will allow the supporting wires to show through in a spider-web pattern. This pattern is readily detectable on aerial photographs and immediately identifies the flat-top.

FIGURE 64 (73K) (1) and (2). -- Counterbalances, surface and buried. These substitute for stakes and holdfasts in unstable or rocky terrain and must also be camouflaged.

FIGURE 65 (72K) -- Camouflage materials require constant maintenance. This gun crew changes cloth garnishings in net as the color of surrounding vegetation changes.

b. Other maintenance consists of preventing tracks around the outside of the flat-top, keeping wires uniformly tight, preventing stakes from working out of the ground, and repairing or changing garnishing as necessary (fig. 65).

33. HANDLING OF NETS. -- a. When not in use, twine nets should be folded carefully in such a way that they can be unfolded easily. One good method is shown in figure 66 (e) through 66 (a). The net is spread out and stretched by pulling at the corners. The detail folds the long edge toward the center, making accordion folds 18 inches to 2 feet wide. The edge binding is kept on top and toward the center. When these folds have almost reached the center of the net the other side is folded in a similar manner.

FIGURE 66 (a). (65K) -- Fold along long dimension. (b). -- Accordion folds made from both long edges toward center.

FIGURE 66 (c). (57K) -- One folded section is lifted and placed on top of the other, with edge rope away from men. (d). -- Folding lengthwise into final 2-ft. folds.

The second bundle of folded net is lifted and placed on top of the first, with the edge rope on top and away from the men. If the net contains an embrasure, this edge is folded last so that the embrasure can readily be identified by touch in the dark. Embrasures should be laced closed before folding, with one of the quick-release devices shown in figure 67.

b. The folded net is now stretched lengthwise to remove irregularities. Each end of the folded net is truned in about 2 feet, and two flat rolls are formed by folding from the ends toward the center of the net. The final step is to place one of these rolls on top of the other end and to tie the net securely.

c. Nets should be dried before storing to prevent rotting and mildewing.

34. EMBRASURES. -- Embrasures for high-angle weapons should be about one-third the dimension of the net from front to rear and should be placed in the middle of one side-the longer side, for rectangular nets. It is difficult to cut a straight embrasure in old-style nets where the twine runs at a diagonal to the sides, but it can be done by following a row of knots which runs perpendicular to the sides. Use one of thc quick-release devices illustrated in figure 67.

FIGURE 67 (38K) (1).-- Quick-release device -- hinge and pin. (2). -- Quick-release device -- ring and loop.

35. SLOPE SCREENS.-a. Types.-Sides may be added to a flat-top and sloped gradually to the ground. These sides should not make more than a 15degree angle with the net; otherwise, a regular, hard "ridge" line will be formed where the sides join the large net, and the sloped portion will differ in appearance from the horizontal part. They must be very gradual extensions of the top to form a sort of inverted shallow bowl with a flat bottom. If the area to be covered is not too large, a dome-shaped slope screen can be constructed (fig. 68). There is little or no deflnite flat area in this type of net. The sides slope continually in gradual curves to form an angle of 15� or less with the ground, again forming an inverted shallow bowl, but with a round bottom.

b. Construction.-The required number of vertical uprights is erected over the area. Between the tallest uprights of the installation and the outer boundary of the area, additional uprights of intermediate height are erected in line. No. 10 wire run along the top of these uprights rises gradually from stakes in the ground on one side, up and across the middle of the curve, and down again to the opposite side. A long, gradual, uniform slope is formed. To maintain this uniform and even-sloping surface, many cross-sectional or radial wires should be used. In planning slope screens, care should be taken that radial wires do not cross the opening for an overhead embrasure, if one is required. The finished framework should be a strongly constructed, taut umbrella of wire, fastened to wooden supports.

c. Garnishing and framework.-Large sections of garnished netting are rolled over the framework and laced together. The garnishing, in general, is equivalent to about 60 percent of the complete net area and must be carefully thinned at the edges.

d. Access routes.-For permanent installations of great size, it is possible for access routes to be made by means of tunnels which emerge beneath the slope screens, thus doing away with the necessity for constructlng doorways in the outer edge of the net, and also preventing the wearing of telltale tracks or paths. Hedges, actual or simulated, may provide means of covered access to the sloped net.

36. OTHER SCREENS.-Road screens may be used to conceal from ground observation either actual or decoy road blocks, to conceal the character and extent of movement along a road, and to hide turn-offs and loading points on roads at supply points and other installations. Similar screens conceal new construction for coast artillery trom marine observation, and conceal supply points and command posts. Overhead screens are, of course, the only ones effective against aerial observation.

FIGURE 68. (73K) -- Slope screens gently rounded to conceal building.

FIGURE 69 (62K) (1) and (2). -- Road screen used tactically prevents enemy ground troops from determining nature of obstacles from a distance.

a. Screens for concealing road blocks may be made of any material-debris, vegetation, or artificial materials variously garnished. One technique is illustrated in figure 69. The idea simply is to hide the block so that the enemy must make a choice either to run over the screen and risk what is behind it, or to stop and investigate it. If he stops, he is vulnerable to fire. If he tries to run over it, he cannot take advantage of possible weak points in the obstacle.

b. Vertical screens to protect bivouacs from enemy patrols are made of natural materials to blend with the background.

c. Screens have a further use as deceptive devices in barren areas, where they can mask gun positions from ground observation.

FIGURE 70. (100K) -- Overhead screen conceals short stretch of access route.

d. Turn-offs and loading points at command posts, headquarters, bivouacs, dumps, and other installations may be concealed by over head hammocks such as shown in figure 70. These are made of garnished wire netting supported on No. 10 wire strung between trees. Another method of improving overhead concealment at such points is to pull branches and small trees together at the top and fasten them with wire or rope.

37. SMOKE. -- Smoke is sometimes used offensively to screen an operation such as a river crossing, or defensively in hiding or reducing the visibility of large fixed installations such as railroad yards, docks, and water supply dams (fig. 71).

a. Method of smoke screening. -- The use of smoke to protect rear-area points involves production and maintenance of large clouds or screens over a broad area. The most satisfactory method of accomplishing this, from the standpoint of economy of materials and operating personnel, is with oil as a medium. Vaporization and condensation of special oils in a mechanical smoke generator produce a dense, persistent smoke with ample obscuring power to hide surface objects from aerial observation.

b. References. -- For further information on smoke, see FM 3-5, Tactics of Chemical Warfare; FM 3-50, Antiaircraft Smoke and Smoke Generator Units; TM 3-240, Meteorology; and TM 1-282, Tactics and Techniques of Air Chemical Sprays.

FIGURE 71 (68K) (a). -- Smoke generators in the first stage of screening a port.

(b). -- Heavy smoke hides city from aerial view.

SECTION IV. REDUCTION OF TONE CONTRASTS

38. COLOR. -- a. Reduction of color contrasts makes an installation inconspicuous. A light plane on a light runway is most easily located by its shadow (fig. 72 (1)), while on a darker runway it is picked up through its own contrast with the background (fig. 72 (2)). If we reduce all color contrasts -- a dark plane on a dark runway -- the plane practically disappears from view (fig. 72 (3)).

b. Color differences are less perceptible as the distance from object to observer increases. Installations subject only to high aerial observation can be toned down with one simple shade of a color that matches the background. This is more concealing than poorly chosen disruptive patterns.

FIGURE 72 (66K) (1). -- Light-colored plane on light-colored runway is revealed by shadow of plane. (2). -- Light-colored plane on dark run- way is revealed by contrast. (3). -- Dark-colored plane on dark runway blends well. Shadow, though less conspicuous, is still there, revealing plane.

FIGURE 73. (69K) -- Texturing runway with wood chips to produce darker tone from the air and reduce contrast with surrounding area.

39. TEXTURING. -- Texture affects tone because of the way in which it casts shadows and reflects light. As with colors, texture applied to match an object to its background must have the same general characteristics as the background. A concrete runway, painted the color of adjacent grass, does not look the same to the observer because the grass has texture and the concrete has little or none Given texture by the application of wood chips or other texturing materials, and painted a suitable color, the runway becomes less conspicuous (fig. 73). Other flat surfaces require similar treatment.

SECTION V. DISRUPTION OF FORM

40. GENERAL. -- Disruption of form is accomplished by adding irregular outlines to regular-shaped objects and by using disruptive patterns in paint or other materials (fig. 74). Paint is the most commonly used material; but cinders, for example, break the outlines of runways when applied in irregular patterns on the runway surface and carried onto the shoulders. Disruption of form is not a positive preventative against direct observation or aerial photography, but it aids in confusing the aim of the bomber, tank gunner, or rifleman.

FIGURE 74 (194K) (1) and (2). -- Silhouettes, disruptive pattern change form of barracks building.

41. SILHOUETTES. -- Disruption of outline, form, and shadow of buildings is aided by the use of silhouettes, usually attached to the edge of roof surfaces. They must be irregular and bold. Materials such as plywood or stiff chicken-wire-garnished frames have the necessary firmness and durability. Scaffolding, nets, or framed decoy structures are also used (fig. 75).

42. PATTERN PAINTING. -- a. In pattern painting, the object is painted two or three contrasting colors, applied in irregular shapes. Colors should be similar to the predominant colors in the object's surroundings (fig. 76). Objects are painted darker on top and lighter below, for the reason that upper parts receive and reflect more light. This principle is especially important in vehicle painting (fig. 77). Patterns should extend around corners and over vulnerable points.

b. There is no definite rule governing pattern sizes. They depend on the size of the object, the size and type of its surroundings, and the type and range of enemy observation. Patterns should be as large as practicable. When seen from a distance, small patterns blend into one monotonous color, and do not destroy the shape of the object. Small color differences cannot be distinguished by aerial observers.

FIGURE 75. (63K) -- Terraces of garnished nets conceal outline of building.

c. Painted patterns alone do not give reliable concealment. The object must be seen against the background for which the colors have been chosen to be effective.

d. Disruptive painting of vehicles is tactical protection. It is protective coloration intended to conceal vehicles in well-selected positions, when they are not on a road and not disclosed by tracks, under circumstances which do not permit the use of drapes, and where early

FIGURE 76. (61K) -- Bold disruptive pattern painting continued over adjacent ground with patterning of cinders and pine needles breaks up characteristic lines of a building.

FIGURE 77. (91K) -- Three contrasting colors are used on this tank destroyer. Colors are olive drab and black to match the dominant colors in temperate zones, and white for undercarriage. Upper parts are darkened, lower parts lightened in color to compensate for differences in amount of light striking these parts. Elements of pattern extend around corners and over vulnerable points.

resumption of movement is expected. It is ineffective while a vehicle is in motion. The type and size of pattern to be adopted is determined by the characteristic pattern of the terrain in which the vehicle will operate, its tactical use, and the type of enemy observation expected to be encountered. A pattern should blend with its background and should be sufficiently disruptive to make the form of a vehicle unrecognizable. Whenever the fire mission permits, a pattern-painted vehicle should be sited so that the dark portions of the pattern blend with adjacent shadows in the position. In some theaters, standardized patterns have been established for various types of vehicles. There are many tactical situations where such standard patterns are superior to a single neutral color, although they lack the wide adaptability of the single color. Equipment is painted darker than its surroundings. Using the standard camouflage colors, the following basic color schemes are recommended for painting patterns on military objects. Other combinations are used as required by local terrain colorings.

(1) Temperate zone. -- Olive drab, field drab or other light color to match terrain, black.

(2) Desert. -- Sand or earth yellow, earth red or other light color to match terrain, black.

(3) Arctic. -- White, olive drab.