Need help to solve the problem with the number of armed forces

Question

Good day! I asked this question on Reddit, but unfortunately I couldn't find the answer I needed there.

So, I'm going to write a book in the space opera genre, and since I'm very weak in things related to astronomy and space, but I have an idea and desire to write, I try to do things in which I'm strong - politics, characters, organizations, the entire inner world and lore of the galaxy. My problem is that I have a galaxy inhabited by trillions of intelligent species. The main power of the galaxy is a theocratic absolutist empire with strong militaristic traditions (classic space Prussia). And the problem is that I can't correlate the total population with the size of the space fleet.

I determined that the size of the entire army (ground and space) can be from 1 to 15% of the total population. The space fleet is the main military branch of the army - it takes 40% of the recruits from the total number of armed forces.

I have calculated the general type of the fleet - it includes aircraft carriers, battleships, cruisers and destroyers, has its own aviation in the form of classic bombers, interceptors and so on. Smaller ships can be used for patrols and law enforcement in the star system. So, given the average number of crew per ship, I can't make the star fleet large enough. In order to have interesting enough space battles, the interstellar fleet of a huge empire cannot exceed 15 million ships (which is equivalent to a total call-up to the front). Instead, on average, a fleet of 20,000 ships requires 40 million soldiers, and another 10-20 million on support ships and logistics, food collection and repair of damaged ships. This, in the end, gives me a number of several billion.

The population of the empire is 222 trillion. And even having reduced this number to a more modest 2.2 trillion, I cannot bring the size of the interstellar fleet to the required 40%. What solutions can you suggest? Please, I really need discussion and advice.

I myself have come to the following possible solutions:

1. Drastically reduce the population of the empire and the galaxy. This will allow us to achieve the stated goal, but will sharply reduce the scope and possibility of creative freedom, since I will not be able to create a sufficiently large number of large industrial centers.
2. Even strong militarism cannot argue with the fact that the war of the future will require the creation of more and more complex mechanisms and technologies. Because of this, it is simply impossible to call up a large number of people to the front - they are needed at home. In factories.
3. Despite its enormous strategic importance, the production of new ships is such an expensive and complex task that it is simply impossible to go beyond a fleet of several million ships. The backbone of the army consists of planetary defense forces, which can make up to 80-90% of the total armed forces. These are garrisons, landing forces, space infantry that protect ships from boarding, large armies necessary for making forced marches and capturing large demographic and industrial centers. Thus, the ground armed forces are heavily dependent on the actions of the space fleet and are forced to obey them as an elite, but at the same time, due to the huge number of worlds, the headquarters regiments are the largest unit of the army, but their decentralized nature prevents them from becoming the main military force.

Answer 1

This is a Frame Challenge

You're making a mistake when you believe the size of any military can be reduced to a percentage of the population.

• Israel requires every citizen to serve in the military, but the time served varies based on sex, service, and occupation.

• The United States has a draft that can compel all to serve, but it hasn't use the draft since the Vietnam War (1973) due to sufficient volunteer enlistment.

There are a variety of ways to ensure there are enough people to serve including:

• Voluntary enlistment
• Mandatory service
• Conscription/Draft
• Selective compulsory service
• De Jure compulsory service
• Combinations (Source)

But all of this ignores the three biggest factors that determine the size of any military:

1. Active conflict (war).
2. Active threats (potential war).
3. Economics.

Of the three, the most ignored when it comes to worldbuilding is #3. One of the reasons why the USSR collapsed was the military budget was way too high. The country couldn't afford the military. Here in the U.S., overspending on the military can cause inflation. In fact, military spending is inherently inflationary and must be carefully balanced with other national policies to ensure a healthy economy.

Why do I say this? Because I think you're putting the cart before the horse. You want to get to the space battles part of your story before you've fleshed out your worldbuilding. If you can handwave the economics that control just how big the military can be, then you can handwave how big the military is and this whole question becomes irrelevant.

Worldbuilding forward and backward

• Forward worldbuilding is when you design the world before you write your story and your story is forced to comply with the world you designed.

• Backward (or reverse) worldbuilding is where you develop aspects of your story and then pause to build the world to rationalize the story — resolving worldbuilding conflicts as you do.

Pretty much all storybuilding uses a combination of forward and backward worldbuilding. Do you have an active war? Do you expect the Empire to win it? Then your worldbuilding must conform to the requirements of the story. We call this narrative necessity. The story conflict dictates the worldbuilding rules which, in turn, would dictate such things as the economic strength of the Empire during that conflict. (Which makes for a much richer story experience.)

Not ready to worry about the wars yet? Then focus on building the world, which means on the one hand developing the military structure (ranks, ship types, weapons) and on the other hand is the actual military disposition (serving ships, equipment, and people and their age/condition/quality). During the raw worldbuilding process you're worrying about structure first. Disposition is nearly impossible without the story.

Case in point: even if you try to work out the peacetime disposition, how can you do that without knowing the circumstances of your various worlds and peoples?

In short: You're making a mistake

You're trying to create a "snapshot" of your military, or perhaps a "starting point," but such things only exist in the context of the story. We can talk about Ancient Rome all we want including the nature of her armies... but we can't know a "snapshot" of the size of Rome's military without picking a specific date and asking, "what was it on that date?"

So, stop worrying about the size of the empire's military and focus on developing the empire including technologies, research capacity, industrial capacity, economy and culture. Then develop the rules of the military such as the types of ships and weapons, support and logistics facilities, administration and training, etc.

Then start writing your story. The size of your military will be nearly automatically determined as you start writing about parades, diplomacy, small/large conflicts, strategic locations/resources, and the nature of the empire's enemies.

Ever with an eye on economics. Many a war has been lost because someone couldn't afford to continue fighting it.

Answer 2

Remember that soldiers are effectively nobility who eat but don't work. It is not realistic to have more than maybe 1% of the population in the military in peace time, when the country is not engaged in a life or death Great Patriotic War.

Men are 50% of the population. Of those 50% only one third are of fighting age, remaining 15%. But those men are the ones with the greatest work capacity and in the greatest demand in the economy. So maybe 5% to 10% of them are just sitting idle and playing soldier. Overall this results in 0.75% to 1.5% of the population in the armed forces.

Oh, and about the number of people in the Navy: for each person serving on an active ship you have anywhere between 10 and 20 people serving on shore. Building ships; repairing ships; making cannon and ammunition; making uniforms, paint, lines, food, and so on; analyzing intelligence; training recruits; etc. etc. These support personnel can be military personnel or civilian contractors, but this is a distinction without a difference -- in any case they are pampered nobility who need to be supported by the productive part of the economy.

Answer 3

Logistics

The tooth-to-tail ratio measures how many support personnel are required for each combat soldier. You can find various statistics but it seems to be about 4:1 in the US, from some quick Googling. You may find different numbers for other militaries (I saw an estimate of 2:1 for the UK), but the US is clearly the best proxy for your galactic empire. While you might have some economies of scale and automation, I'd suggest that cross-galactic logistics create an even longer supply chain. That suggests that if the size of your military is 2.2 trillion (although 1% is awfully high for a technologically advanced military to maintain in peacetime), you can reasonably put a trillion to a trillion and a half in support roles, perhaps even more.

Galaxies are big [citation needed]

Even if you have FTL, unless it's basically instant it takes a long time to get from one side of the galaxy to the other - long enough that by the time you get there, both your planet and the enemy are long gone. That means you need several fleets stationed at various bases around your empire, and any battle is only going to involve one or two of those fleets. That being the case you can easily make the military as big as you want and the battle as small as you want without any conflict.

Answer 4

Drones.

Each small ship in the fleet would be accompanied by at least a couple of semi-autonomous drones capable of following the lead of the human pilots. Larger ships would have many more.

The AI used to pilot them and pursue targets would need to be sanctified, cleansed of all taint of the artificial - it would for the sake of any battle need to be declared as having a soul, albeit a primitive, animalistic one, but a soul. It would follow church doctrine, keep the peace, and fight any unholy enemies on command.

Similarly, repair-systems would be automatic, the internal functions of the drones would be performed by internal mechanisms.

The fewer the humans, the greater the number of AI-pilots.

It strikes me that there's no reason that an AI ship need be distinguishable from a human-crewed one.

Answer 5

Forget population, think gross domestic product.

Your nation might be able to put 1% or even 10% of the population into the armed forces -- the latter is pushing things -- but they cannot give all of them starfighters or battleships.

It is sustainable to put 5% of the gross domestic product into defense. That might go as high as 10% for quite some time, but that would be what one calls a 'war footing' of the industry and society. Much more, and they are deferring maintenance and re-investment, pure scientific research, and so on.

Those 5% have to pay the salaries of your troops, and the salaries of the people who built their equipment, and the parts and raw materials which go into the eqipment. You might 'get away' with paying riflemen or supply clerks a below-average salary, but not the rocket scientists.

Answer 6

My problem is that I have a galaxy inhabited by trillions of intelligent species.

Secondary frame challenge: the number of species is implausibly high.

We live in a fairly large galaxy, which has between 100 and 400 billion stars. A trillion intelligent species would imply between 10 and 2.5 species per star, which seems awfully high, given their likely tendency to have wars between species while they are at low levels of social development.

How about having only a few billion species, rather than a few trillion? It still sounds a lot, but it's less obviously crazy.

Answer 7

On way to get lots and lots of people involved in your star fleet is to treat them as a kind of 'fuel'. Like put a few million people extra in cold sleep on each ship.

Maybe those sleepers get waked up, connected to the ships AI to feed new inspiration in, so it doesn't degenerate? And when the ship AI has absored all the new stuff, it can get creative enough to plot a course for your FTL drive. And then you put that load of crew to sleep again and wakeup the next for the next stage of FTL flight.

Attacking fleet oilers in such a case would be a terrible tragedy and loss of life. In addition, you get some fun housing and supply problems when you scale down the fleet, as you suddenly have a few more billion people to feed and house instead of in cold sleep.

Answer 8

Interstellar wars are fought by automated starships, basically drones maintained by robots. The ruling empire has been around for a long time and has been able to construct a large number of such ships or perhaps they captured them from the previous rulers in a successful rebellion. There are people in fleet, but not on every ship and the fleet will not have a large number of personnel, certainly more than 1, but no more than a 100.

As long as planets pay their taxes and do not attack their neighbors, they are left alone. other wise a fleet of automated star ships appear and if the planet does not surrender, it is attack from orbit and basically destroyed.