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.