The different branches were distinguished by the colours of the cap - see the table. Cavalry normally wore shakos or plumed helmets, reserving red kepis with light or dark blue bands for wear in barracks. General officers wore (and continue to wear) kepis with gold oak leaves embroidered around the band.
With the adoption of sky blue uniforms and steel Adrian helmets in 1915 to replace the conspicuous peace time uniforms worn during the early months of war, the kepi was generally replaced by folding forage caps. Officers however still wore their kepis behind the lines., French police (since replaced with caps), French Foreign Legion, Unrelated RATP hat, French Gendarmerie, French Army. Following the war the kepi was gradually reintroduced in the peacetime French army. The Foreign Legion resumed wearing it during the 1920s; initially in red and blue and then in 1939 with white covers on all occasions. The bulk of the French army readopted the kepi in the various traditional branch colours for off-duty wear during the 1930s. It had now become a straight sided and higher headdress than the traditional soft cap. This made it unsuitable for war time wear and after 1940 it was seldom seen being worn except by officers. An exception was the Foreign Legion who, previously just one of many units that wore the kepi, now adopted it as a symbol.
The French National Police have however discarded their dark blue kepis, adopting a low peaked cap. The reason given was that the kepi, while smart and distinctive, was inconvenient in vehicles.
Former cavalry units wear light blue kepis with red tops and silver braid (for officers) and insignia. Other colours include all dark blue with red piping (for artillery units), dark blue with red tops (line infantry) and crimson with red tops (medical). The "dark blue" of officers' kepis is actually very similar to black.
The Greek Army of the same period wore dark blue or green (the latter for cavalry) kepis, and continued the same style of headress in khaki when field uniforms of that colour were introduced in 1910. Other armies that favoured kepis during the final period of colourful uniforms that ended with World War I included the Danish, Portuguese, Dutch, Italian (officers only), and Romanian armies. Even the Japanese Army adopted French-style kepis for senior officers in full dress, as well as for their Gendarmerie units and military bands. The Norwegian armed forces used kepis until World War II and retains them for the full dress of officer cadets.
While the law and order forces wore bright red caps, the armed constabulary was conspicuous by its blue kepis. After Indian Independence, the former French colonial territory was integrated into the Union Territory of Pondicherry and the bright red kepi continues to be the headgear of the constabulary both for the local and the armed police signifying the cultural and administrative legacies left by the former colonialists.
Brisbane bus inspectors continued to wear black kepis with decorative braid until the introduction of a French blue kepi in 1987.
Source: Wikipedia > Kepi
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