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Wikipedia:
In military tactics, a camisado, or camisade, is a surprise attack occurring at night, or at daybreak, when the enemy are supposed to be asleep.
The word is said to have come about from an attack of this kind, in which, as a means to recognize one another, the attackers wore shirts, chemise or camise, over their armor. The term was very common in the 16th and 17th centuries.
Camisado has been erroneously applied to the shirt worn over armor during a night attack.
The term come from Spanish camisa (shirt): when the Tercio had actions, (skirmishes) of around 50 men attacking at night with minimum equipment, only sword and dagger (although some soldiers could carry arquebus or musket), and they were dressed only with a white shirt, (thus the Spanish word es:encamisada), in order to kill in silence as many enemies when they were sleeping. This has been perfectly reflected in the film Alatriste, based on the main character of a series of novels written by Arturo Pérez-Reverte, The Adventures of Captain Alatriste (Las aventuras del Capitán Alatriste).