Bicorne

The bicorne or bicorn (two-cornered) is an archaic 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.

On formal occasions such as a prorogation speech, the Lord Chancellor of the United Kingdom wears a tricorne hat, but the other Lords Commissioners wear bicorne hats.
Members of the Académie française wear the habit vert (green habit) at the Académie's ceremonies. The habit includes a black jacket and a bicorne in the cocked-hat style, each embroidered in green.

Students at the Ecole Polytechnique wear a bicorne as part of their Grand Uniforme (GU). Female students used to wear a tricorne hat but now also wear a bicorne. The bicorne also formed part of the historic black and red full dress of cadets at the French Military Medical School ("Ecole de Sante des Armées") until this uniform was withdrawn in 1971, except for limited use on special occasions. The bicorne is still worn by the members of the Cadre Noir in full dress uniform.
The uniform of the horsemen of the Spanish Riding School of Vienna includes a bicorne.
Diplomatic uniforms worn on such occasions as the presentation of credentials by ambassadors normally included bicornes worn with feathers and gold or silver braiding. Until World War II such uniforms were worn by even junior embassy staff but now survive only for ambassadors in a few long-established diplomatic services such as those of Britain, France, Belgium and Spain.
At the annual Trooping the Colour in London, British generals taking part in the ceremony wear the scarlet-and-blue full dress of their rank, which includes a bicorne. Certain officers of the Brigade of Guards who hold administrative positions such as that of quartermaster wear bicornes (described as cocked hats) in full dress instead of the usual bearskin.