The Aquila, or Eagle, was a battlefield symbol for the Roman Legion. General Marius introduced the Aquila in (or around) 104 BC. The Aquila was mounted on a pole, and carried by the aquilifer. The loss of a legion's aquila in battle was a seen as a serious disgrace, in much the same manner as a US Army cavalry flag or battle flag in the 19th Century.

The aquila is also one of many Roman symbols co-opted by the NAZIs (along with the strait armed salute of the 'Heil Hitler'), although it was not, to my knowledge, used in battle, but rather as a symbol during party rallies.