A galactic empire is a tenuous thing, hard to run and harder to hold. Here I will gather my ruminations on the matter.
Additional Ideas (7)
The most obvious, expensive, and probably important aspect of a galactic empire is that of the Imperial fleet. Without a large and equiped space navy, a galactic empire could not exist. While the most obvious use is the projection of force, either through capital weaponry, loads of starfighters, or simply deploying troops to a world to fight, there are other possibly more important uses.
The prospect of sending a FTL signal across the galaxy should be a daunting to nearly impossible task. Short to medium range comm links can be held by sub-space relays, communication satellites and comm bases located in centralized locations. These trunks of communication work well for their localized areas, but communication with unexplored regions, or regions cut off by space debris, nebula, etc, would be serviced by communication ships, couriers.
The Space Merchant Marine
Commanding unknown numbers of worlds, each has something of value that is a luxury somewhere else. The blood-sligs consumed as waste meat on one world, sixty light years away are a delicacy and haute cuisine. The man who can haul a load of the creatures there can stand to make a proper fortune, or loose one in the process.
Outside of luxury items, basic goods such as material for building ships, radioactives for engine cores, and other large bulk, relatively low value goods will also be in high demand. A kilometer long ship takes a massive amount of resources to build, so demand for refined steel, nickle, and other metals will remain steady. In times of war or massive ship building, the price could skyrocket. Pirates representing multi-world confenderations could find steeling kiloton loads of steel and such more time and cost profitable than actually buying or processing the goods themselves.
The most basic need, without a starship capable of FTL travel, there is no getting there from here. Generational ships could also work, but such an empire would be massivly slow that it would neither be fun to play in, or fun to manage from a game perspective. Worlds could rebel, have two or three generations to prepare for the Imperial responce, which itself would be a recolonization effort with a bloody military edge.
There are plenty of overused tropes, possibly the most famous being the single biome world (Dune was all desert, Dagobah was all swamp). While this trope works well enough for an encounter of the week, or a few scenes before whisking off to another planet, it is pretty unrealistic.
A dome world is a planet that either lacks an atmosphere, or has one that is unbreathable. Space is at a premium, population would be rather strictly controlled, and an outbreak of a virulent disease could potentially wipe out a large fraction of planetary population.
Knuteria is a heavily industrialized Dome World. The surface has a thin atmosphere of volatile sulfer and hydrocarbon gas which is poisonous and mildly corrosive. Most of the population lives in underground warrens and cavern facilities. The elite have upper levels and access to some of the scattered surface domes for an open view of the sky. The industry is mining and heavy manfucturing as the planet has no biosphere to protect and is untenable for terraforming.
With apologies to Warhammer 40K, a hive world is one where the population has exploded beyond what is normally sustainable by the planet. Hive worlds require regular supply of food and raw materials to continue operations without famine, riots, and civil rebellion. Life tends to be cheap on these worlds, regardless of their primary industry or output. The empire does have a great interest in maintaining hive worlds as they are excellent sources of manpower for the legions upon legions of Imperial army.
Almost any core planet and most certainly Earth would be hive worlds, their base population massive and growing.
The opposite of the hive World, the Agro-world exists with a minimal population and is tasked with feeding the hungry maws of the hive worlds with food produced and shipped out. Agro worlds are often the targets of raiders and pirates due to limited defence and available resources.
Stodemeyer II is a valuable agro-world, produced a massive amount of food, mainly in the form of wheat and sea kelp. The planet has a minor population, less than a few hundred million, all engaged in agriculture. Mechanization is common, and few are active in picking crops be hand. While Stodemeyer wheat is a bulk commodity, the planet's red and white wines are known for light years beyond it.
Water World - Planet has large surface water, and little land. Likely to be used for agriculture.
Desert Planet - Little or no water, functions like a dome world, but often without domes. Water is a commodity, industry and mining are common.
Metal World - a resource rich planet, often with a hostile atmosphere. Populations are low, industry and mining are high.
Alien World - Contains remnants of alien life, or currently has alien life, humans are a minority or are non-existant.
The Imperial Military is a massive organization, it takes a huge military to hold and defend a large percentage of the galaxy. There are rogue factions, splinter states, rebellions, alien incursions, plagues, famines, riots, and wolves baying at the doors.
The massive majority of Imperial Troops are garrisons and militias drawn from the worlds they protect. These troops are supported by taxes from the planet administration, supplied with local produced guns and light armored vehicles and other basic gear. It is easy to call them the lowest and least skilled, but a unit of Hive world Militia could easily be a match for trained regular army soldiers. Industrial world militias tend to be heavier armed, while hive worlders have much larger numbers.
Akin in level to militas and garrisons, Auxilliary units are pulled from those ranks and are placed in service with the regular imperial army. not considered front line troops, Auxilliaries mop up, hold conquered territory, and bolster numbers within units and formations that have taken heavy losses.
Regular Imperial Army
Like militia and garrison forces, these units are primarily composed of infantry, but tend to have more uniform training, better arms and armor, and access to larger and more powerful vehicles. While a planetery militia has to make due with what it can produce on it's own, an Imperial Army unit has access to the military output of industrial and forge worlds. These units do most of the fighting, from defending targets, to waging campaigns to turn back aliens, suppress rebellions, and the like. Joining the Imperial Army is generally a life sentence, few make it back to where they came from, most tend to retire on whatever world their last campaign was on, or die in the trenches, guns in hand.
Veteran And Elite Army
Like the Rangers and the SEALs, the veteran and elite elements of the Imperial military have specialized purposes, equipment, and training. While armor and infantry brigades will be regular grade troops, the power armor infantry, mech units, and other exotic types of weapon systems with be the veteran and elite units.
An army travels on it's stomach, or so the saying goes. This might not seem like a major issue at first, but when an Imperial legion deploys, it is putting tens to hundreds of thousands of men on the ground. While some worlds are able to support the food requirements of these soldiers, many such as already resource strapped hive worlds, or non-food producing barren, or dome worlds cannot. This is even more of an issue if water is not available. (This is accounting that ships will have water recycling facilities, so waste water is reprocessed into drinkable water)
So a 100,000 strong unit of Imperial soldiers would literally be a plague of locusts on an unsuspecting or prepared world. Local foodstuffs would be quickly purchased or commandeered by the unit, in addition to the rations that would be transported by supply ships. An extended campaign would require an extended supply line to bring the most basic of necessities to the soldiers, food and water.
An unsavory aspect of soldiering is that men like women, and soldiers dont have the option of bringing their wives and girlfriends with them. While the army of the future is just as likely to have women carrying guns, it would likely remain a male dominated field. With the above scenario, a 100,000 strong force of Imperial soldiers would quickly destroy the prostitution of a world it was occupying, subjugating, or repairing and refitting on. The Comfort Brigade is a unit comprised of prostitutes that follow a larger military unit and 'service' the soldiers in the field.
A River of Lead and gasoline
Ammunition and fuel do not produce themselves, and while it is tempting to say that the entire Imperial army is armed with energy weapons and fusion reactors, this is somewhat... unlikely. Bullets versus beams will be discussed in greater detail later, but missle launchers, rail guns, mines, and other war consumables will have to be supplied to the army in the field. Unless a world has a viable munitions industry that the army can use, or capture, it will have to import it's own ammunition and fuel.
The main purpose of this entry is the fuel and ammo depots, centralized and fortified locations that the Imperial units will operate from and viciously protect. These depots and the lines of supply that lead from them are the arteries that keep the soldiers in the field. Hitting a supply depot for the Grand Imperial Galactic Army will be just as effective as blowing up a depot was in WWII.
The 'L' Word
The L word is not Love, it's Logistics. An army needs food and water for it's men, ammunition and fuel for it's weapons, and some sort of recreation to distract it from the fact that it is a brutal tool for killing and destruction. The Logistics Arm of the galactic military is massive, commanding dropships, fleets of supply and tender ships, and massive numbers of petty officers, quartermasters, and clerks.
Any company waging a large scale war will need a continual supply of this, which can easily be as bulky and expensive as ammunition.
A military force, unless it is comprised of bare fisted men fighting on foot, will have vehicles and weapons to maintain. This ranges from the obvious guns and tanks, but less visible gear such as radios, transports, and medical equipment. A large variety of equipment can be put into the field at any given time, but providing parts and replacements becomes a challenge.
Standard Template Vehicle
There is not a single factory on a single world that supplies all of the military's vehicles, be they tanks, mechs, fighters, or whatnot. It would be easy to equip with what was available from the various industrial and forge worlds, but such a hodgepodge would not be effective in combat, and a nightmare to support logistically. The Imperial Standard Template is a protocol for mass produced vehicles to be built on the same designs and using roughly the same materials. If an assault gun, engineering vehicle, radio-CIC vehicle and APC can all be built on a Standard Template Light tank, then the parts required can be streamlined. All would use the same wheels, tank treads, armor plating to varying amounts, engine parts and whatnot.
The downside to Standard Template design is that the most economical design will win out the contract, and not the most effective one. As numbers increase, and the Imperial armor groups would be indeed massive, mediocrity becomes more prevalent than excellent designs. An industrial backed rebellion might be able to put generally superior tanks onto the battlefield, but the Empire would always be able to put more armor on the ground, and win through sheer numbers.
Mechs and Tanks
In the futuristic scenario, the Empire has access to tanks, walking tanks, robots, and assualt mechs, but it seldom uses all of these forces in a given location, and the most common Imperial vehicle is the basic tank. The main reason is that mechs and vehicles with legs tend to be on the high end of the tech scale, and require more extensive maintenance, more expensive parts, and replacement parts that are not readily available. A tank, on the other hand, barring exotic weapons and whatnot, can be repaired with the supplies found on a moderately industrialized world, and basic components can be made by commandeering industrial facilities and retooling them.
In the far flung future, the combustion projectile weapon, the bullet firing gun, will still have a place in the military. While there will certainly be lasers, masers, missles, plasma weapons, and other sorts of explodium, the basic gun will still have a major role to play in the defense and campaigns of the Empire.
Bullets are Cheap
Bullets are inexpensive, and the guns that fire them are also, meaning that a low tech level planet would be able to manufacture their own weapons as well as supply their own ammunition. Moderately advanced worlds would be able to mix energy and projectile weapons in their arsenals. Standardisation would be common to make sure that if the forces of the Empire were deployed to a world, that they would have access to ammunition they could use for their own guns in addition to the militia's firearms.
It is also a common conceit that lasers dont use ammo, and it is true, they dont. However they have to have a power supply, either in a munchkin-esque onboard power source (micro-reactor) or through the much more likely avenue of a battery or power cell. These cells would function like ammo clips, and would have to be replaced during a firefight. The old cells could be discarded like shell casings, but it is much more likely that they would be kept for recharging. This means that either a soldier has to carry his dry cells, or one of squad's or platoon's soldiers would have some sort of rechargepack to keep the lasers humming.
Making a basic gun will be more simple than making a laser weapon, plus the technology behind the design will be extraordinarily venerable and reliable. While this is not to say that lasers would be technological challenges, they are more advanced and require more upkeep than a basic firearm. Another level is that lasers inflict damage by heat, and do not have armor piercing capability, or knock-down power. A bullet can be made to cut through armor, and will knock a soldier or alien off of it's feet. This is one area where the Star Wars blaster takes a hit, as it combines energy and kinetic damage, which makes it neither type.
Munitions ad Nausuem
With an army that likely numbers in the millions, possibly even the billions, they will require a vast amount of guns and ammo. While this seems like an unneeded expense, it is a farming, nationalized industry where planets with growing economies can enter the arms industry making guns and bullets, with an assured buyer in the Imperial Army. Another variation is that a laser is a laser, and can only be made stronger or weaker, wheras a gun can fire a variety of ordinance, tracers, smoke rounds, rubber riot rounds, armor piercing, and the like.
A savvy unit will mix beams and bullets in their arsenal, as armor that can protect from impact tends to be vulnerable to heat, and ablative armor tends to not resist impact well. An army prepared for a laser assault with ablative armor will be in for a sore surprise when Imperial troops open fire with autoguns and vise versa for the flak armored foe who is cut down with lasers.
While it is easy to imagine a massive codex of imperal laws and decrees, Imperial Law is actually rather simple.
1. Pay your taxes to the Empire.
Each planet has a set tax quota based largely off the estimated gross planetary product. More productive worlds pay heavier taxes than colonies and worlds supported by the Empire, such as science research worlds, penal colonies and the like. The quotas are set be regional offices of the Empire, and various politics can come into play, mostly between said officials and the leadership of the various worlds. A crafty planetary despot could conceal his planet's actual gross product, while a wealthy industrial sector might pay off the office of the assesor to lower their rate. On the opposite, a seditious world could see a higher tax rate, or a world that regularly fails to meet it's tax demand could see a visit from the Imperial Military to replace the current power with one that can pay it's taxes correctly.
2. Supply Troops and Supplies to the Imperial Military as required.
The Military is one of the Empire's largest expenses, and many worlds are able to supplant part of their tax load with supplying war materials. Mostly heavily industrialized worlds tend to do this. It is easier and less expensive to supply the military with a few thousand tanks a year than pay the same in credits. In wartime, certain worlds would be subject to military drafts, and temporary seizure of industry. Facing a major alien threat or multi-world rebellion, the military command can conscript infantry brigades by the hundreds from moderate to heavily populated worlds. It can also sieze military assets of said worlds, offering a tax credit in reimbursement. While often stern and heavy handed, the Empire really doesnt outright steal from it's subject worlds. It cannot exist with a 0% approval rating.
3. Put down treason against the Empire.
Each world that is part of the Empire is expected to maintain a status quo, mostly of not actively opposing the empire or it's interests. This is enforced at varying levels on different worlds, a liberal world might only oppose actual armed organizing, while a tyrannical world might punish even speaking ill of the Empire.
The laws of the worlds under the Empire are largely untouched by Imperial rule. Thus slavery is legal on some worlds, illegal on most. This applies to substances, such as drugs and weapons, as well as services such as prostitution. Look hard enough and you can find a world where your vice is a legal industry. This means that if a criminal can escape a solar system where he commited a crime, the authorities of that star system cannot legally persue him. Most star system governments have procedure for capturing and extraditing extra-solar criminals, but quite a few are safe havens for said criminals.
In the Imperial setting, Bounty Hunters are much more common. Given the amount of red tape that is involved with notifying law agencies in other solar systems, extradition, and dealing with worlds that do not extradite, or are borderline lawless, bounty hunters provide a valuable service. While there would certainly be those like Boba Fett, the majority are going to be more like Mobile Police than heavily armed mercenaries. With a set bounty, hunters would apprehend their target and return them to the system they were wanted in. To prevent murder, Imperial law requires every effort be made to apprehend the target alive, rather than shooting on site.