What are the pros and cons of a client state based sci-fi empire?

Question

I'm working on building a sci-fi world and I had an idea for how to cut down on the sheer amount of bureaucracy that a massive (say, 200 planets) empire would require. What if the central government ran a system of client state like planets instead of directly annexing each of their conquests? In this set-up, the conquered planet or civilization would be allowed to have self-rule under a new government formed by the empire. The client states would be allowed to have land-based militias, but no space-fleets. The central empire would set a specific quota of tax and manpower for the client to give to the state and army, respectively, then leave the government on their own to figure out how to acquire these things.

The pros I can see off are that it makes bureaucracy much easier for the central empire and can potentially make the transition easier for the conquered worlds. The primary issue I see is that these client states could be prone to rebellion if the central empire ever grew weak. Thoughts? Am I missing something obvious here, or does this seem practical?

Edit: Added more information

Thanks to @nullpointer for pointing out a few things I failed to include. The FTL travel of the universe operates on a jump-drive technology with relatively limited range (say, 2 lightyears every day). The exceptions exist in areas where natural or artificial wormholes have been set up. These wormholes require a lot of resources and time to produce, however, and rarely exist in these hypothetical client states. The Empire in question is (at the time the story takes place) working on building waystation wormholes to make transit easier, but right now travel from the home planet to distant client states take weeks or months. Communications in this empire can only travel as fast as the fastest ships, so they're locked to about the same timeline.

Finally, a bit about the empire's motivations. On the home planet, political careers are driven by military successes, i.e. a candidate has to have won x many victories to be eligible for x position. Because of the wormholes near their planet that connect to other planets, they discovered a few other civilizations before the jump drives or even militarized spaceships. This allowed the dominant state on the home planet to finally complete their hegemony without concern for a collapse of their political system and transition into a spacefaring empire. The larger civilizations (this empire included) of the galaxy nearby retain a mutually lucrative trade route that generally keeps them from conquering one another. That leaves smaller, typically less advanced civilizations as targets.

If the general agreement is "yeah, this should work fine", then here's a secondary question: would the empire want to maintain garrisons (either space or ground-based) in client states, or would that cost too much/lack justification?

Answer 1

WillK has provided a great description of the Federal model and he is indeed correct in saying that many countries have done 'well' with such a system, although well is perhaps a matter of interpretation depending on your goals with such a model.

Two countries that come to mind that are Federal in nature are the USA and Australia.

I'm going to expand on Will's answer by providing some pros and cons from my experience in a Government context. Let's start with the benefits;

Expansion
Because the states that join forces retain their own sovereignty (only giving up specific rights to the federal govt) it means that adding new states is a relatively simple exercise. In the case of the USA, they have literally 'bought' states and territories in the past, the most recent of which was Alaska (IIRC). If there is an existing province or state that wants to join the federation, in theory they are entitled to apply to join. Leaving? Well, like Will states that can be a cause of contention and attempts have led to civil war in the past. But, assimilating new territories is certainly a lot simpler.

Mutual Providence
Providing a defense force for a large country with a large population is more cost effective than trying to build a defense force for a small country, or worse yet, a large country with a small population. Also, certain states may be rich in minerals and the like, but not have strong agriculture. A federation allows different states to contribute to the wealth and prosperity of its citizens in different ways and provides for a domestic homogenisation of resources (state A's minerals get shipped around, as does state B's wheat, etc.) without the added complexity of diplomacy or currency issues. This concept easily expands to education, technical capability and other information services.

Diversity
Different states may have different environmental constraints, belief systems, and needs from its neighbours. In a Federal environment, that state has the right to conduct some affairs in accordance with those needs. It's a flexible arrangement by virtue of the state still retaining at least part of its sovereignty. In the US for instance, each state can collect its own taxes, and run its own social welfare systems, etc. In Australia, they have a much broader remit because they have a restrictive constitution (everything at the federal level is prohibited unless the power is specifically granted in the Constitution) but in practice, this doesn't work because one thing that the states are specifically prohibited from doing is raising their own direct taxes.

There are (however) a few pitfalls...

Fragmentation
It may seem like the USA and Australia have uniform codes of law and that they everyone in these countries is subject to the same rules, but that perception is very thin. In Australia for instance, every state as a separate criminal code and when something is being made illegal at the federal level, what's really happening in the background is the federal govt works with the state govts to get them to enact uniform laws in each state. This can be time consuming and very inefficient, especially if not all the states agree on the new law. What this means is that if you're the kind of dictator that wants to micro-manage your states, this model isn't for you.

Disenfranchisement
Just because the federation of your states is a good deal, doesn't always mean that all your states are going to recognise that. The USA discovered that during the debate about slave ownership and the resulting Civil War. In Australia, there is discontent in some states who contribute significant mineral wealth to Australia but feel that they are short changed in terms of federal funding for services. Unless you have REALLY strong communication and good relations with all your states, this sense of being taken advantage of can build in certain regions without you noticing, especially if funds or other critical resources are being centrally redistributed.

On a Galactic Scale
Your ability to expand would be a big plus, especially if you treat every planet as its own state for the purposes of this model. The defense and redistribution of resources arguments make for great selling points, but the sheer scale you're talking about means that diversity almost forces fragmentation among the member states. Given that different planets are going to have different atmospheric, agricultural and mineral resource needs to begin with, this is only going to be exacerbated. Ultimately, the federation can thrive IF there is a strong unifying need among the member states, like defense.

But the one mistake you can make here is to try and micromanage the states in question. At the galactic scale, this federation becomes much looser and you're probably better off leaving most states to do their thing, only providing some principles to which 'their thing' must conform. Things like democracy, term limits, freedom of movement for all citizens, etc.

You won't achieve cultural homogenisation and that's actually a good thing. Most cultural practices tend to form around environmental necessities or conveniences; The British sailors (who came from cold climates) often mistook the minimal dress requirements of Polynesian people as a sign of a primitive culture rather than a natural reaction to a hot, humid climate.

What you hopefully will achieve is a political homogenisation; setting a minimum level of human (?) rights, how government is formed and how often it is replaced, freedom of movement, how it contributes to the welfare of the federation, and the rights it receives in resource distribution and defense in return.

If that's enough for you, then this can be an ideal form of government for states that have such distances between them. Given the political motivations you describe, you could almost think of each state as a franchise; they get to run things more or less how they see fit so long as they recognise a federal patron and conform to the rules that have been set for the broader federation.

Answer 2

You propose a federal system of government. https://en.wikipedia.org/wiki/Federalism

Federalism is the mixed or compound mode of government, combining a general government (the central or 'federal' government) with regional governments (provincial, state, cantonal, territorial or other sub-unit governments) in a single political system...

According to Daniel Ziblatt's Structuring the State, there are four competing theoretical explanations in the academic literature for the adoption of federal systems:

Ideational theories, which hold that a greater degree of ideological commitment to decentralist ideas in society makes federalism more likely to be adopted.

Cultural-historical theories, which hold that federal institutions are more likely to be adopted in societies with culturally or ethnically fragmented populations.

"Social contract" theories, which hold that federalism emerges as a bargain between a center and a periphery where the center is not powerful enough to dominate the periphery and the periphery is not powerful enough to secede from the center.

"Infrastructural power" theories, which hold that federalism is likely to emerge when the subunits of a potential federation already have highly developed infrastructures (e.g. they are already constitutional, parliamentary, and administratively modernized states)

There are many countries that have done very well with federal systems. So too your proposed galactic federation. As you state, the sub governments do not have need of big militaries and should not be permitted to raise them. There is a risk of civil war if "client states" as you say decide to secede.

Answer 3

First, consider prior art:

• Especially with the need for conquest, there is the obvious Roman analogy.
• There is an early science-fiction roleplaying game, Traveller, where the main human state works on this principle. "The Imperium rules the space between the planets, not the member planets themselves."
• One might argue that the Federation of Star Trek works that way, minus the conquest angle.

Both fictional worlds have generated countless fan-based writings how their system can or cannot work. Some comments in addition to those by Tim B:

Just how much interstellar travel and commerce is there, relative to the size of the planetary economy?

• Are they tightly integrated on the scale e.g. the US and Canada are today? If so, it becomes important to have standards for things like the screw threads and power supply voltages. Can a client-state-based empire provide that?
• If they are not very integrated, how does the empire extract taxes? A planet might sign over a trillion planetary dollars which then sit in an account and pay for the embassy compound or the bar tab of soldiers on shore leave. Unless the money is reinvested on the planet, then after decades or centuries the empire would own most industry on that planet, still will no means to extract the wealth.

Are there better integrated rivals?

• It would be in the interest of the empire to foster economic and technical progress on all planets to increase their industrial base and to get a bigger navy for further conquests. Can they do that with a client state model?
• Is the navy itself built on the single central planet, or do contingents come from client planets? What is their loyalty?