Just out of curiosity i checked how hard is nowadays getting information about armies. Without using wikipedia, due to it's limited reliability. Public information include regiments, their recent missions, quite often where are they deployed (with some exception, but thats "fog of war", mostly for special forces. and even for them not always). Of course, they didn;t had internet, but We're not talking about some random guy checking it out of pure curosity, but about a ruler, that has some spies.
An example: British army has 36 regular infantry baons, and 18 reserve, organised into 18 regiments. 1st Batallion scotts guard is located in Catterick, in north Yorkshire, in mid 2015 it will be relocated to Aldershots.
US 1 armored division is located in Fort Bliss, Texas.
Australian 1st division is located in Brisbane.
The only think that limits me is my knowlegde of languages, so I can't check f.e. Russian army. But thats all, the ledger is actually a good depictation of this basic espionage that every country has (just like You don't have to pick administrative IG to have any administration at all)