According to Wikipedia, war bonnets (warbonnets or headdresses) are worn by honoured Plains Indian men. In the past they were sometimes worn into battle, today they are worn primarily for ceremonial occasions. They were seen as items of great spiritual and magical importance and their beauty was considered to be of secondary importance; the bonnet’s real value lay in its supposed power to protect the wearer. Warriors wore the headdress in the belief that the power of the feathers would help them avoid injury.