Bicorn hat

The bicorne or bicorn (two-cornered/horned or twihorn) is a historical form of hat widely adopted in the 1790s as an item of uniform by European and American military and naval officers. It is now most readily associated with Napoléon Bonaparte but in practice most generals and staff officers of the Napoleonic period wore bicornes, and it survived as a widely worn full-dress headdress until at least 1914.

Descended from the tricorne, the black-coloured bicorne originally had a rather broad brim, with the front and the rear halves turned up and pinned together (in English, the shorter front brim was called "the cock"—hence "cocked hat"—and the longer rear brim was termed "the fan"), forming a semi-circular fan shape; there was usually a cockade in the national colours at the front. Later, the hat became more triangular in shape, its two ends became more pointed, and it was worn with the cockade at the right side. This kind of bicorne eventually became known in the English language as the cocked hat, although to this day it is still known in the French language as the bicorne.

Worn in the side-to-side "athwart" style during the 1790s, the bicorne was normally seen fore-and-aft in most armies and navies from about 1800 on. This change in style coincided with the flattening out of the pronounced front peak of the original headdress. The French gendarmerie continued to wear their bicornes in the classic side-to-side fashion until about 1904 as do the Italian Carabinieri in their modern full dress.

Some forms of bicorne were designed to be folded flat, so that they could be conveniently tucked under the arm when not being worn. A bicorne of this style is also known as a chapeau-bras or chapeau-de-bras.

The bicorne was widely worn until World War I as part of the full dress of officers of most of the world's navies. It survived to a more limited extent between the wars for wear by senior officers in the British, French, US, Japanese and other navies until World War II but has now almost disappeared in this context.

...
Wikipedia