"'Camouflage' as stated in Military Intelligence Service Information Bulletin No. 13, 'is any and every means of hiding or disguising yourself from the enemy; misleading him as to your position, strength, and intention; confusing him so that he wastes his blows and falls into your ambush.'"
Above is a quote from the web page called Lone Sentry: Notes on Camouflage (WWII Tactical and Technical Trends, No. 32, August 26, 1943)
Deliberate camouflage (as opposed to what nature provides, for example animal fur that blends in with local colors and textures) has probably been made use of since people became smart enough to figure out that if they didn't want predators or enemies to know where they were (or if they didn't want the animals or people they themselves were stalking to realize they were close by and about to lunge for their necks or their food), a good way to "hide" was to cover oneself in such a way as to blend in with the surroundings or look like something very innocent (a rock, a bush, etc.), or perhaps (this strategy might have come just a little later than the "hide behind stuff" idea) to throw some rocks as far away as possible in order to cause a distraction. I have a feeling that learning about camouflage was one of the very first things taught to young humans from earliest times.
The point of camouflage is, after all, deeply entwined with such basic laws of survival as: Eat; do not let yourself be eaten and Kill (when necessary, even when not for food) and do not let yourself be killed.
As time passed (and lots and lots of time did pass), surely humans continued to develop better and better camouflage that worked where they lived and hunted and considering what their enemies (and prey) were like, and certainly as their brains got bigger and they got smarter they thought of new "tricks" such as adjusting their movements (e.g., if you're pretending you're a rock, do not move at all; if you're pretending you're vegetation, be sure to sway, in the right direction, when the wind blows), making (or not making) certain noises, devising all sorts of distractions, and so on -- A person just sitting on a tree stump cracking nuts with a rock, letting his thoughts wander, could probably come up with dozens of creative camouflage strategies in one lazy afternoon.
So, one might wonder why on earth one sees paintings showing armies in the 1700s and 1800s, say, where they are doing everything seemingly backwards, purposely drawing attention to themselves rather than trying to hide themselves. They wore colorful uniforms, tooted their horns, beat their drums, carried large, fluttering flags, and marched along (or rode their horses) in neat lines, very easy to hear and see and pick off with rifles or arrows or cannonballs (or whatever weapons they were using).
Bataille_de_fontenoy (Battle of Fontenoy) - Painting by Édouard Detaille (1848-1912) - French Academic painter and military artist.
Could it just be that somewhere along the line men got to be so macho that instead of trying to hide themselves in dangerous situations, they took great pains to show themselves in order to demonstrate that they had no fear (to impress each other, and themselves, as much as the enemy, no doubt? Think about those who are hunting for animals rather than fighting with other people; they are more interested in keeping themselves hidden).
Apparently this is the case at least in part* - but some of them finally realized it was a lousy idea to purposely attract attention to themselves (rather than being impressed with their bravado, the enemy thought they were fools and went in for the kill). And this is where artists came in.
At the time of the First World War, when the idea that it was not terribly smart to let the enemy know precisely where you are took hold, artists were employed by the military to create designs that would transform uniforms, tanks, ships, guns, buildings, etc. in such a way as to keep them hidden from enemy eyes. Such artists as Abbot Thayer, Jacques Villon, André Dunoyer de Segonzac, Franz Marc, Oskar Schlemmer, Edward Wadsworth, Arshile Gorky, László Moholy-Nagy, Franz Mark, Thomas Hart Benton, Grant Wood, and Ellsworth Kelly, among many others, served as camouflage artists during World Wars I and II.
Artists know how to design camouflage because they use the same kinds of techniques in their art, for similar purposes (though in the case of artwork it isn't a life or death matter). Every time they compose a picture they must consider the sorts of things that must be considered when designing camouflage.
They must know such things as how to lead the eye where they want it to go, how to create a focal point that draws attention to itself and away from other things (and how to make sure there is no unintentional focal point that attracts the eye), how to make things that are in plain sight hardly noticed at all or even seem to not be there unless you're looking hard, how to make insignificant things seem important, how to make separate and even unlike items seem to blend together into one whole, how to divide up something that's really big so that it no longer looks like one big massive item, and so on.
In order to accomplish these kinds of objectives artists have a large arsenal of "tools" to work with, just for example: color (hues, intensity), tone, gradation, placement, relative sizes, angles, shapes, quality of edges, distances between things, textures, linear elements, and lighting effects. They can make things look light in weight, heavy and solid, transparent, wet, dry, close, distant, hard, soft, man-made, or organic. They know how to make things look serene or chaotic (or even just plain confusing), and so on and on.
It must be very interesting and challenging to work on camouflage projects, and being under the tremendous pressure of knowing that what they come up with had better work or people - maybe a lot of people - might die would certainly motivate artists to do their very best. Certainly they learned much that they needed to know from non-artists in the military who knew what needed to be done and probably had some excellent ideas of their own that they figured out instinctively, but the artists themselves were necessary because they could come up with all sorts of ideas only they could think of (having had constant experience trying to achieve similar effects in their artwork) in order to accomplish the goals the military had in mind.
NOTE: (This refers to what precedes the * in the paragraph above beginning with "Apparently")
* Yes, men were making a show of their bravado, but to be honest there were also some compelling reasons for this seemingly foolish way of dressing and otherwise drawing attention to themselves (see Wikipedia article called "Red coat (British army)" and also Wikipedia article on Military Uniforms for their reasoning). However, when ammunition became more accurate and deadlier, and "cleaner" (no clouds of dust produced when firing that hid people), and after airplanes were invented, the military became interested in camouflage.
SOME OF THE MORE INTERESTING ARTICLES ON CAMOUFLAGE I READ AT LEAST PARTS OF IN PREPARATION FOR THIS POST:
This us a very informative article at Wikipedia called Military Camouflage
This one explains and illustrates Gestalt Theories of Perception. It's called Laws of Camouflage
Here it tells about the use of uniforms beginning with the creation of standing armies: A Brief History of Camouflage Uniforms
This tells about the artists who designed camouflage in wartime, and also how camouflage has been used by artists since then: Art, Culture, and Camouflage
Here's a good article telling about how artists were employed during the first World War to devise ways to camouflage ships, aircraft, etc. It's called Masters of Disguise
Another interesting site is called Camouflage, Concealment and Decoys Study Guide (armystudyguide.com)
_____Free Newsletter - See bottom of this page.