A little educational story:
The eagle as a symbol appeared in ancient greece as a sign from zeus and were supposed to be a sign of favor by the gods. Greek citizens cultur and religion spread across the mediteranian, which is why it appeared in Italy.
Each legion (usually consisting of 5000 men) had one standard made with a golden eagle. Which became the very symbol and pride of the roman armies.
Hitlers use of the eagle is as 90% of everything else of symbolism he used, stolen from greater days of greater men/civilizations. The iron cross was the mark of a teutonic order (knights during the medieval days), the "nazi cross" or "sun cross" originates from norse mythology. The "nazi" salute was also used by the roman armies to their leaders.
Since Hitler "percieved" or atleast used these to promote his ideas of the supreme being "übermench" (flatly stolen from nitczhe) and the supremecy of the Arian race he used these ancient symbols which most people respected and blatantly used them for his own gain.
German armies NEVER had legions, there has never been an army (except the french foreign legion) after the roman empire that used "Legion" as a term of size of a unit. Germany used the modern expressions of armies IE, troop, batallion, corps, division etc etc.
There are still several nation/armies that use some form of eagle as a symbol still. USAF is one example of such, the german armies still have the iron cross on its tanks/aircrafts.
www.google.com is your friend before making stupendos posts.