This pair of photographs dates from World War I, when they were most likely distributed by the US Government to newspapers and magazines for publicity. For example, they were published in the April 1918 issue of Popular Science magazine (p. 588), along with an article claiming that "Moving picture men are going into the 'camouflage' business." These photos are examples of how theatrical "special effects" could be used for battlefield purposes. The cannon on the left is a "sham gun," or what was then referred to as a "Quaker gun," a means of making the enemy think that the opposition was greater than it really was. On the right is a photo in which all the various props (buildings, cannon, smoke) are not at all what they appear. The photos were made on a movie lot in Hollywood, as explained in the text that continues—
Some of the recruits of a newly organized United States Army [camouflage] corps are experienced motion picture men. A full company has been raised in the Los Angeles studios alone. Another company stands ready to be enrolled. The men are eager to used their skill to "make up" imitation cannons, tanks, machine guns and other grim actors for their parts at the Front.
A recent demonstration, held in one of the great Los Angeles studios, revealed the possibilities of "camouflage." The wizards of illusion raised a village in the twinkling of an eye; tore it down with equal dexterity, and in an incredibly short time substituted a startlingly perfect "camouflage" forest. The fairy-tales of our youth, in which genii and fairies raised and removed castles by magic, seem to bid fair to come true in these days of seeming miracles.
During World War II, theatrical set designers, animators and special effects artists contributed to both civilian and military camouflage in even larger numbers. Much of this is documented in Ronald Naversen, The Scenographer as Camoufleur. PhD dissertation. Carbondale IL: Southern Illinois University, 1989.