The Army ID, is the unique code which each army is assigned when an Army is created, the code is also the page name of the armies page and is used for a lot of automated reporting and calculations, so it is vital that the ID is not modified in any way.
The ID will be in the following format for Legions:
L designates that it is a Legion @ can vary from 1-5 characters and is the Legios number in roman numerals
- will be a four digit number which is the armies designation number within the Legion
As other factions become available their Army ID will be in a similar format with a different leading letter and middle section but always a four digit disgnation number.
This Army ID is perpetual as long as you keep the army listing itself, if the army page is deleted then the number will be returned to the pool to be reused. So if you are intendning on keeping your army active on AUS30K, you can feel confident is using this ID for other pieces of fluff or other things. It will be used at any events which participate in Campaigns and is very useful when playing against other players participating in the wars in Australis Ultima.