The Guardian Corps
If you want to see real fighting and make an actual difference against the evil from the other worlds then you want to be a Guardian.
The souls that take the path of the Gaurdian must undergo the most rigorous training of the body and become the most powerful soldiers in all of Archonia.
Numbering over one hundred thousand they are main fighting force in the military. Once a year they take a crusade to the mortal plane of existence where they try to save souls and fight off the evil found in the world between worlds.   
The Sentinel Corps
There are those who want to devot their lives to the safety of others and keep order in society. The sentinel Corps is the place for these souls.
With over one billion souls it is the largest branch of the Archonian military. Mostly acting as guards and policing the cities, they very rarely see anything more than trivial disputes which are settled on the spot by an Adjudicator  
The Adjudicator Corps
Only the wisest will succeed as an Adjudicator. Where the Guardian corp trains the body, the Adjudicator trains the mind.
Te become an Adjudicator one must undergo the purge where they are confined to a cell for as long as it takes for their mind to be completely impartial. There they are indoctrinated to be perfect machines of truth and justice.
Once complete they continue their training in combat and tactics. When the safety of Archonia is threatened they become the officers and tacticians that answer to the commander's of the different Corps.