André Mare, Elm at Vermezeele (Sketchbook)
Camouflage had to fool enemy observers and also allow better and more reliable observation. It was for this reason that imitation trees in metal were produced and painted to look like an actual tree. Being hollow and armour-plated, they allowed a soldier to climb up and look out through slits in them. They were usually set up at night to avoid the enemy detecting the substitution. This technique required as accurate a copy of the tree it was to replace as possible, as is shown in Mare's sketchbook.
"I found myself in a huge hayloft (a very nice workshop!) and I painted nine 'Kandinsky's' (...) on tent canvas. This process had a very useful purpose: to make artillery positions invisible to reconnaissance planes and aerial photography by covering them with canvases painted in a roughly pointillist style and in line with observation of the colours of natural camouflage (mimicry) (...) From now on, painting must make the picture that betrays our presence sufficiently blurred and distorted for the position to be unrecognisable. The division is going to provide us with a plane to experiment with some aerial photographs to see how it looks from the air. I'm very interested to see the effect of a Kandinsky from six thousand feet."
Franz Marc, Letters from the Front, Fourbis, 1996.