One of the strangest and most clever disguises ever used in war was by the Germans against the British during World War I. During a standstill between the trenches in Belgium, the Germans felt trapped and needed a way to spy on the British who were hiding and what they did to solve the problem was ingenious.
The trenches were surrounded by trees, and when the Germans attempted to climb the trees to spy, they were immediately shot down. To solve the problem they took sections from a steel pipe and formed them to look like a tree. Inside the pipe, which was plated and 25 feet tall, there was a ladder and a seat behind a window so they could spy.
The only problem was that it would have been pretty obvious if a random tree sprouted overnight, so they waited until nighttime, cut down a real tree, and put the fake one in exactly the same place. For the next seven months, even after the British had tunneled under German trenches and taken the area, the fake tree remained undetected. To this day, it remains one of the smartest and simplest devices used to spy on an enemy!