The four Zouave regiments of the French Army wore their traditional colorful dress during the early months of the First World War. The development of the machine gun, rapid-fire artillery, and improved small-arms obliged them to adopt a plain khaki uniform from 1915 on. From 1927 to 1939 the "oriental dress" of red fez ("chéchia"), blue sash, braided blue jackets with waistcoats and voluminous red trousers was reintroduced as off-duty dress for re-enlisted NCOs and other long-service regulars in the Zouave regiments. It was also worn by colour guards and other detachments on ceremonial occasions. White trousers of the same style had earlier been worn as an item of hot-weather dress. The four regiments were distinguished by the colours (red, blue, white and yellow) of the "tombeaus" or false pockets on the front of their open-fronted jackets.