Hello everyone

Can anyone help me in ER Diagram

Represent part of the military command structure of the armies of world. It is desired to represent every command unit and all army personnel, along with their ranks and personal details. Each country has one army who has a Commander-In-Chief. Each army is divided into a number of field armies. Each field army has between 90,000 - 200,000 soldiers and is headed by a General. There is only one Field Marshall in each army. Not all generals head a field army.

from reading the senior I think Soldier, Marshall, Commander etc. are roles so that They are not entities.

I think that entity type is :
Country (countrycode, country_name)
Army (armycode, army_name, country_code)
solder( id ,name)

but I am not sure about that

So please if any one can help me?