The setting is: Imperial Guard (Astra Militarum) in the Warhammer 40.000 universe. I find their regimental structure too unrealistic, sending only a few regiments to defend/attack a given planet.
So I want to come up with a better military structure to span an entire planet. I'm not interested in battalion/regiment/... structures, but more on how many generals you need for which functions, how many commanders should report to the next higher-up. Who needs how many aids, etc.
I will expand the question with what I've already come up with. But want to post it already so as not to lose what I've already typed.
1. Size of the miliary
The planet has a population of about 10 billion people. About 10 percent will be drafted in the army. If about half of this (500 million) stay "at home" to defend the planet, train, study (to achieve higher ranks), etc, 500 million troops can be sent out to different planets to conquer those of defend them from the aliens.
2. High command
I can imagine the following high (e.g. four-star generals) being required:
- Chairman of the joint chiefs of staff
- Chief of staff of the army
- Chief of staff of the navy/coast guard
- Chief of staff of the air force
- One commander for the troops of each continent
What would their general staff look like? Which composition?
3. Lower commands
I'm a bit lost here as well. What would the lower structures look like? For example, each continent would be divided into smaller regions, do each get another commander and general staff?