A shield is a piece of personal armor held in the hand. Shields are used to block specific attacks, whether from close-range weapons or arrows, by actively deflecting them, as well as for passive protection by deflecting one or more attacks during combat. Shields vary greatly in size and shape. In prehistoric times and in the era of the first civilizations, shields were made of wood, animal hides, reeds, or thin pieces of wood woven or braided together. Shields were used by infantry, knights, and cavalry.
In the 20th and 21st centuries, shields have been used by specialized military and police units to carry out counter-terrorism operations, hostage rescues, riot control, and breaking sieges.
