Many armies around the world since the middle of 20th century uses berets as part of their uniforms, the first army was in the early 1880 of the 19th century of French Alpine troops (Chasseur Alpin). Army beret tilted to the right at the top, a few European countries are to the left.
Berets as a military advantages: cheap and easy mass production using various colors to distinguish between different forces; packaging or in your pocket, do not preclude the use of headphones. Last point is very important for soldiers in the armored vehicle. Disadvantage is that no, cannot cover the Sun and storm.