A 1998 ''Franchise/StarWars'' RealTimeStrategy FourX game by [[Creator/LucasArts LucasArts]]' with a gameplay similar to ''Stars'''.

The player assumes the role of a military administrator and takes control over either the Galactic Empire or Rebel Alliance and must overthrow the other side. In order to balance gameplay, the sides are more closely matched than one would expect.

'''Rebel goals'''
# Capture Palpatine
# Capture Vader
# Capture Coruscant

'''Imperial goals'''
# Capture Mon Mothma
# Capture Luke
# Destroy the Rebel base

Special gameplay events include: Luke goes to Dagobah, learns of his heritage, teaches Leia about their family, and the two (along with Chewbacca) rescue Han if he gets captured by bounty hunters.

One of Rebellion's unique aspects which sets it apart from other games of its genre (and especially from the later Star Wars RTS ''VideoGame/EmpireAtWar'') is the heavy focus on gaining and maintaining the loyalty of planets rather than simply trying to take them all through brute force.

Also known as ''Star Wars Supremacy'' in the United Kingdom and Ireland.

In 2016 [[Creator/FantasyFlightGames FFG]] released a board game version that uses similar mechanics.

!!Tropes seen in this game include:

* AllianceMeter: A central facet of the gameplay. Each and every inhabited world in the galaxy has its popular support split between the Empire and the Alliance. If you attain a super-majority of popular support on a planet it will come to your side willingly. On the other hand, conquering a world that is loyal to your enemy will require you to leave behind some troops to keep the world in line, else the locals rise up and try to restore their preferred government. Planets are organized into sectors and events at one planet can affect the loyalty of all the other planets in that sector. Planets will react positively if you get other planets to come to your side or leave your enemy willingly, destroy enemy ground troops through Planetary Bombardment (unless you hit a civilian structure), or win a major space battle. Conversely, you will lose support if you destroy civilian structures through Planetary Bombardment (intentional or not) or suffer a disastrous defeat in a space battle.
** The Death Star has some rather unique effects on the loyalty system. On one hand, utilizing its Destroy Planet function causes the Empire to lose support on every planet in the galaxy. On the other hand, the presence of a Death Star can reduce garrison requirements or even [[ShameIfSomethingHappened immediately subdue uprisings on Imperial-held worlds.]]
* ACommanderIsYou:
** The Alliance starts off as The Guerilla Faction. Their starships are vastly outmatched by the Empire's Star Destroyers, their military leaders aren't as effective as those of the Empire, and a good chunk of their otherwise-loyal planets start off under Imperial occupation. On the other hand, the Alliance Headquarters starts on a random Outer Rim system and can be moved at any time (unless there's an Imperial fleet on top of it), the Alliance starfighters are vastly superior to the Imperial TIE models and are a threat to Imperial starships, and liberating the occupied worlds can win the Alliance some major political points that can win over half a sector or more to the Alliance cause.
** The Empire starts off as The Brute Force Faction. They start the game with several Star Destroyers and the ability to build more (though that takes a very long time with the starting Shipyards). Their ships vastly outclass the Alliance ships and they are also more adept at conducting Planetary Bombardment thanks to the Victory Destroyer. They also have more and better military officers at their disposal. However, their TIE Fighters simply cannot deal with the (dangerous) Alliance fighters at all. They must also work to diplomatically secure their planets which start under military occupation, else the Alliance liberate them and cause a political crisis across a sector. And unlike the Alliance, the Imperial capital is no secret; its always Coruscant, and the Empire must constantly devote resources to its defense.
** As the game goes on, both sides move toward being The Balanced Faction. The Alliance quickly addresses its starship deficiency by researching the Nebulon-B Frigate and Mon Calamari Cruiser very early, while the Empire likewise addresses its ability to deal with Rebel starfighters by researching the Lancer Frigate and TIE Interceptor.
* {{Ambadassador}}: Anyone with the stats for it can be sent as diplomats to neutral planets. Most of the named ones such as Luke or Vader, and many of them badasses already, can also be very effective diplomats.
* AnyoneCanDie: Anyone except the main characters that is, even if they're on a planet destroyed by the Death Star, they're simply "captured and injured."
* ArtificialStupidity: Even on the highest difficulty setting, it's almost impossible to lose the game unless you do so on purpose (and even then you have to coax the enemy into it). This is thanks to the enemy not really taking advantage of the game's mechanics the way they should (like building huge fleets or converting some planets to construction hubs).
* AwesomeButImpractical: The Death Star is at best this and at worst ShmuckBait. The Death Star does have some legitimate uses; it can instantly destroy starships in space battles, has a massive carrying capacity, a bombardment modifier four times that of even the Victory II, its mere presence can reduce garrison requirements and subdue uprisings, and of course it can instantly destroy planets which is very handy against targets like the Alliance headquarters or any other REALLY well defended planet. On the other hand, it costs a massive amount of time and resources to build, it can be destroyed by starfighters or even sabotage, and its destruction can cause your characters to become traitors. Its primary function also comes with a pretty major drawback: every time you destroy a planet, every planet in the entire galaxy gains Rebel support. If you get trigger-happy with that superlaser, you could find yourself on the verge of losing your entire Empire to uprisings. [[https://www.youtube.com/watch?v=MW6OEWF8eNQ Just take a look at what happened when the "GetDaved Fortress of Pain" went on a rampage.]][[labelnote:explanation]]Prior to "GetDaved's" rampage, jnwestray78 as the Empire had a pretty solid hold on the Corellian and Sesswenna sectors, with little to no Rebel support to be found. After "GetDaved" demolished half of the Jospro sector, the Corellian and Sesswenna sectors now had over 50% Rebel support - more than enough to require garrisons to keep them under his control, and this wasn't just limited to those two sectors mind you, but EVERY planet in the galaxy. He obviously did it just for demonstration or entertainment, but had he been playing against a human opponent that move could have cost him the game; Rebel fleets could have liberated a planet or two in each sector and the resulting political shifts would have escalated the situation into an outright disaster by incurring uprisings and massive garrison requirements for pretty much the rest of the game.[[/labelnote]]
* BlackAndWhiteMagic: Fits the trope in spirit anyway. The Rebels ''cannot'' steal Imperial craft. Nor will anyone defect, though they will sabotage their own missions if you sufficiently kriff it up, like losing two Death Stars or something. The Empire has stronger capital ships, the assassination mission, and starts out with a Jedi Knight and a Jedi Master. The Alliance, by contrast, has stronger starfighters, starts out with only ''one'' Force-sensitive (Unlocking Leia's Force-sensitivity is a [[GuideDangIt complicated side quest]]: Luke has to be on the same planet as Vader, and then has to be on the same planet as Leia. But early on, Luke will inevitably be captured by Vader.), and has a starfighter engineer (Wedge). Differences in ship quality tend to be reduced over time, and all Force-sensitives other than Vader and Palpatine improve their stats easily.
* BoringButPractical: Sabotage missions. A successful Sabotage mission instantly destroys its target. Virtually every structure and military unit in the game can be sabotaged, including the Death Star (for which you get a special cutscene if you manage to pull it off). Many Characters are capable of performing Sabotage missions, and both sides can mass produce Special Forces units capable of performing them from the very start of the game. Enemy units and officers at the target location can detect and foil these missions, but you can counter this by assigning additional agents as decoys.
* CanonImmigrant: Incorporates a lot of characters from the StarWarsExpandedUniverse and gives some of them faces for the first time.
* CompetitiveBalance: This is in play late in the game, but not as it begins--the Rebels have inferior capital ships to the Empire and no trained Jedi, while the Empire has no answer to the Rebels' superior starfighters and two Jedi. In addition, the rebels get a slew of other skills to make up for their starship imbalance (see FakeBalance below). Later on the Rebels can research larger ships capable of standing toe to toe with the Empire and Luke can become a full Jedi and then find and train others.
* ContinuityNod: Lots of it! Most Minor Characters have stats and abilities that reflect what they do in the movies and the [[StarWarsExpandedUniverse Expanded Universe]]. Some notable examples are below:
** Lando Calrissian can perform Facility Design Research, which makes since because he ran Cloud City and personally engineered some pretty creative facilities in the Expanded Universe, such as a walking mining city and an underwater mining operation with an underwater casino/observation gallery.
** Bevel Lemelisk is one of the Empire's Ship Design Researchers. HE ENGINEERED THE DEATH STAR!
*** And yet despite being executed seven(!) times for it, the Death Stars you build in this game still have that two-meter wide exhaust port...
** Thrawn of course has a very high Leadership rating and can be promoted to Admiral, but he is also capable of Ship Design Research. Those TIE Defenders the Empire has? Thrawn came up with something even BETTER: the Imperial Missile Boat.
** In a similar vein to Thrawn, Ackbar also possesses high Leadership, can be made Admiral, and can perform Ship Design Research. He designed the B-Wing.
** Mon Mothma is the leader of the Alliance, and as such has high Diplomacy and Leadership ratings. She is SO important to the Alliance that capturing her is one of the Empire's victory conditions. She is actually a Major Character and thus cannot be killed, but she does not have any special events or abilities like the other Major Characters.
* DecisiveBattle: The battle to take Coruscant definitely fits this trope. The Alliance must conquer Coruscant to win the game, and it is typically defended by a large fleet with many Star Destroyers and TIE Fighters in space, and many shield generators, planetary guns, and troop regiments on the ground. The Alliance must muster a very large and powerful fleet in order to take it. A space battle over Coruscant is one of the few times the AI will fight to the death even if it is vastly outgunned and there is no Interdictor keeping it there, and the number of ships involved makes it likely to be the largest space engagement in the game. Even after the space battle is won, the Alliance Fleet must then bombard its way through the shield generators and planetary guns and finally the troop regiments before it can finally launch the Planetary Assault to take the planet itself. Taking Coruscant is a huge victory for the Alliance; it generates TONS of loyalty for the Alliance on all other planets in the Sessweena sector, causes Imperial characters to become traitors, and completes one of the Alliance's victory conditions. In fact, if the Alliance has already captured Emperor Palpatine and Darth Vader, or the game is set to "Headquarters Victory", then taking Coruscant wins the game for the Alliance. Game mechanics aside, taking Coruscant shows the galaxy that the Alliance does have the military power and resources to defeat the Empire.
* TheDevTeamThinksOfEverything: Since the Alliance has to capture Coruscant to win, a creative Imperial commander with a rather literal interpretation of victory conditions may attempt to destroy the planet with a Death Star in order to prevent it from ever falling into the Rebellion's hands. The developers anticipated this move, however, and if Coruscant gets destroyed, it counts as permanently satisfying the Alliance victory condition for its capture.
* OrcusOnHisThrone: Justified: the Emperor provides a leadership bonus to all Imperial characters if he's at Coruscant.
* EvenEvilHasStandards: Mostly just for game balance, the Empire cannot execute or assassinate any captured rebel characters, even though [[GameplayAndStorySegregation they showed no qualms about carrying such sentences out in the story.]]
* FakeBalance: A result of the game's asymmetrical factions. Although the game bills the Empire as being strong in the early game before the Rebels catch up and both sides become equal, the opposite tends to be true. Due to a number of factors apparently caused by the developers [[DidntThinkThisThrough not thinking things through]], the early and mid-game heavily favours the Rebels; in an unmodded Rebellion game, playing the Empire is seen as a significant handicap and most modders give the Empire a few power boosts to compensate. Notably:
** Although the Empire's early capital ships dominate anything in the Rebellion's hands, it takes quite a while for fleets to really become an important factor, as the initial shipyards produce ships very, very slowly. Unless you want to take hundreds of days to build a single Star Destroyer, the player generally first needs to build numerous construction yards (which takes a while), then get those construction yards to build shipyards (which may also take a while, depending on which planet(s) you choose as your shipyard planets). In the time that it takes the players to do that, the Rebellion will almost assuredly have moved up the tech ladder and unlocked ships that can go toe-to-toe with anything the Empire has on hand (when the Rebellion unlocks Assault Frigates (which doesn't take long), the Empire's advantage in space completely disappears and it takes a long time for them to even return to even footing, let alone reclaim a marginal advantage).
** Even in the early game, while the Rebels have a distinct disadvantage in capital ships, their starfighters knock the stuffing out of any Imperial ship they cross. The Empire has no effective counter until they research Lancer Frigates. And, unlike the Imperial capital ships, starfighters can be produced quickly and cheaply, even from a planet with few shipyards. A rebel fleet composed exclusively of Alliance Escort Carriers will strike terror into any Imperial's heart until the lancers start rolling off the line.
** The rebels always start with Wedge Antilles, who can begin research on new starships as fast as you can get him to a shipyard; the Empire, on the other hand, does not have a research-capable character amongst its guaranteed starters. Unless you are lucky with your random character(s), the Empire will be late to the research game (potentially cripplingly late, if you're unlucky with your Recruitment missions).
** The Emperor's character bonus requires him to stay idle at a base that the rebels are guaranteed to attack sometime; none of the rebel characters' inherent bonuses require them to be stationary OR idle. Made worse by the fact that conquering the base in question (Coruscant) and capturing the Emperor are two of the three victory conditions for the Rebellion, forcing the Empire to put most of their eggs in one basket.
** The Empire always starts with one planet that is forcibly occupied by Imperial troops, yet is loyal to the Rebellion. This planet is something of a ticking time bomb, because it is a ripe target for a rebel Incite Uprising mission. One of the Empire's first priorities is getting a diplomat to this planet and trying to sway it to the Empire's cause (contrast with the rebels, whose diplomats will probably be spending this time recruiting valuable, neutral planets). Worse, if an uprising occurs or the Rebels succeed in freeing the planet, every other neutral world in the sector also winds up joining the rebellion.
** Han's ''Millenium Falcon''-gifted speed is a huge pain to Imperial players, as it allows him to bring a unit of insurrectionists to an Imperial-controlled, Rebel-aligned world and incite an uprising faster than the Empire can get a diplomat and/or troops there to suppress the mission and quell the discontent. Worse, if a planet falls to uprising, it takes most of the sector with it. If the Empire is ''really'' unlucky, the "target" planet will be far from any diplomats and close enough to the Rebel Base for Han to claim the entire sector long before any Imperial response can be mustered.
** The fact that the Rebel base is located in the Outer Rim AND is hidden from Imperial eyes allows the Rebels to start secretly colonizing the rim long before the Empire can get a colonization fleet put together. While the Empire's production planets are easily located and targeted by the Rebels for sabotage or fleet assault, the Empire has to actually ''find'' the Rebels before it can start hindering their production. The Imperials do get one advantage in that they only have to find the rebel base once and destroy it (and it ''can'' be sabotaged), but the rebels also have the option of moving the base as many times as they like, making it very difficult for the Empire to track it down and destroy it for good).
** The number of characters protected by PlotArmor varies between the two factions. On the Empire's side, only the Emperor and Vader cannot die; on the Rebellion's side, that tally includes Luke, Mon Mothma, Leia, Han, and Chewbacca. It's particularly frustrating as an Imperial player to note that it's completely impossible to permanently put any of the rebellion's best characters out of action (though injuring or capturing them can waylay them for quite a while).
* FogOfWar: Your knowledge of enemy activity is very limited. You can only get real-time intel on enemy fleets when they are parked over your planets, and you can only get real-time intel on enemy planets when your own fleets are parked over them, and you normally cannot see enemy personnel or missions at all. Your other option for gathering intel is the Espionage mission which, if successful, will reveal absolutely everything on the target planet at that time and even what is on its way there. However, Espionage results are like a snapshot of what was there when the mission was completed; just because you can now target that Star Destroyer for sabotage doesn't mean it will still be there when your saboteurs get there.
* GameplayAndStoryIntegration: While this game doesn't have much in the way of story, the game's major characters (Luke Skywalker, Leia Organa, Han Solo, Emperor Palpatine, and Darth Vader) do have special events and abilities which reflect things from the movies.
** Luke Skywalker goes to Dagobah early in the game, during which he is completely off the map; unavailable for the Rebels and undetectable and uncapturable for the Empire. He returns with a very large stat boost and increased force rating.
** When Luke Skywalker encounters Darth Vader for the first time, [[LukeIAmYourFather Vader reveals Luke's heritage]] and Luke is automatically injured as a result. Bringing Luke and Leia together after this unlocks Leia's dormant force power.
** While Han Solo is traveling either by himself or with other characters only, he is assumed to be flying the Millennium Falcon and travels with the fastest hyperspace speed in the game.
** Han Solo is occassionally ambushed by Bounty Hunters who try to capture him. If they fail, then they give the Empire intel on Han's location. If they succeed, he is taken to Jabba's Palace and Luke Skywalker immediately drops whatever he's doing to try to rescue him. If Luke fails, then Leia makes her own attempt. If SHE fails then all three are captured by the Empire.
*** If Han is taken to Jabba's Palace while Luke is still on Dagobah, Luke will leave Dagobah prematurely to try to rescue Han. This causes Luke to miss out on a good portion of the stat boost he would have normally gained from Dagobah.
** Emperor Palpatine increases the Leadership ratings of every Imperial character in the game as long as he stays on Coruscant.
** All characters with unlocked force power will automatically detect and foil the missions of enemy force users.
** Lastly, there is a once-per-game event called The Final Battle. If Luke Skywalker is captured after reaching Jedi Student status, he is automatically moved to Darth Vader's location, and then both are moved to Emperor Palpatine. The Final Battle occurs when all three characters come together. The result depends on Luke's force rating: If he is still only a Jedi Student then he loses and remains in captivity. But if he is a Jedi Knight or Jedi Master, then he not only escapes captivity but also captures BOTH Darth Vader and Emperor Palpatine for the Alliance. Remember that in order to win the game (on standard rules), the Empire needs capture Luke, while the Alliance needs to capture both Vader and Palpatine.
** A-wings cannot do Death Star trench runs in accordance with their inability to carry Proton Torpedoes. But [[GuideDangIt the game doesn't tell you this]].
* HelloInsertNameHere: You can name your starships and fleets whatever you like, even downright silly things like naming a Death Star the "GetDaved Fortress of Pain" and its accompanying fleet the "Fleet O' Doom".
* IdiotBall: If you throw A-wings against a Death Star, this is you. Also if you have a Death Star before getting the TIE Defender, or have any ship in a fleet not fully loaded with starfighters.
** Build the Death Star, but don't put any troops or fighters on it. Even better, keep it in a fleet all by itself like that. Now, [[http://www.youtube.com/watch?v=_wYRcpVnVnw remember what we said about even the Death Star being vulnerable to sabotage?]]
** Believe it or not, there's actually a third way to lose a Death Star: repeatedly use it in Planetary Bombardments against a REALLY well shielded planet with lots of planetary guns. The Death Star does take damage from the guns and can actually be destroyed this way.
* JackOfAllStats:
** X-Wings. They are deadly against TIE Fighters but can also deal good damage to starships once their shields are down. They also enhance your ability to conduct Planetary Bombardment. And of course, they are essential for taking out Death Stars. However, they will have a hard time bringing down the shields of larger and more advanced starships on their own, and they are only really useful against such ships once their shields are down.
** Nebulon-B Frigates. They carry two squadrons of fighters each and have good turbolaser and laser cannon power, making them decently effective against both fighters and starships. And you get all of this for a relatively cheap cost. Despite not excelling in any one area, the Nebulon-B is by far the best ship in the Alliance arsenal at the time it comes into play. A group of Nebulon-B Frigates loaded with X-Wings can handle many situations.
** TIE Defenders, for most of the same reasons as the X-Wing. In fact, they are SUPERIOR to X-Wings!
* MagikarpPower:
** The Alliance starts out with relatively bad ships, but they get better quickly since they start out with...Wedge Antilles, who is now apparently an engineer.
** Luke Skywalker. He starts out as a lowly [Jedi] Trainee; definitely better than any other character you have but leagues behind the Empire's two Jedi Masters (whom you must capture in order to win the game under the standard victory conditions). When Luke returns from Dagobah he will instantly jump up to Jedi Student, making him far more powerful than before, though still not quite able to stand up to Palpatine or Vader. But after about 20 more missions after that he will reach Jedi Knight status, at which point things get tougher for the Empire (who must capture him in order to win the game). Even without The Final Battle, Jedi Knight Luke can go toe to toe with Palpatine and Vader without getting captured in the process. Given enough encounters he can injure Palpatine and Vader to the point of having Combat ratings of 0, at which point any non-force sensitive characters or special forces can abduct them with almost certain success.
*** Luke also happens to be the easiest Jedi in the game to raise. In addition to the massive boost he gains from Dagobah, Luke can also gain large boosts from special events when he encounters Emperor Palpatine or Darth Vader (if he doesn't get captured). Luke also gains points for foiled missions in addition to successful ones (again, only if he isn't captured).
* NoCampaignForTheWicked: Averted, although the Empire has fewer big-name characters and its EvilCounterpart of C-3PO is made up for the game. Inverted in that more of the Rebel ships are made up while almost all of the Imperial ones had previously appeared in other sources.
* NonEntityGeneral: The player is this, commanding his chosen side from a secret command center. [[spoiler: If you lose the game, the enemy fleet finds you and blows the crap out of said command center, presumably killing you in the process.]]
* OrbitalBombardment: One of your options when you have a fleet positioned over an enemy planet. You can choose to just blast anything and everything on the planet, or you can choose to target only military or civilian facilities. Destroying military units and facilities without hitting any civilian facilities boosts your sector wide loyalty. Destroying civilian facilities reduces your sector wide loyalty, but if the whole sector already hates your guts then its a nice way to quickly reduce the enemy's resources. However shield generators can protect against bombardment up to a certain strength, and any planetary guns will severely damage or even destroy some of your ships.
* PlotArmor: A particularly egregious example given the subject matter (although possibly meant as a tongue-in-cheek parody of the parent work), most of the "main characters" from the film cannot be killed. If targeted by assassination missions, passengers on a ship that is destroyed, or even on a planet that gets blown up by the death star, they will [[OnlyAFleshWound just be injured]] (and potentially captured).
* PowderKegCrowd: Freshly invaded planets tend to be this. They have high garrison requirements, they suffer losses from smuggling unless you keep a lot of troops or ships in the area, and they can be incited into out-and-out [[TorchesAndPitchforks uprising]] if you don't tend to them quickly. Notably, the Empire has a few of these to start with, and mollifying them is usually the Imperial player's number one priority (unless you want the rebels snatching it - and, very quickly, the entire sector it's in - out from underneath you).
* SaltTheEarth: A valid tactic to use if your opponent hasn't invested in shield generators. Send a reasonably powerful fleet into their systems, sweep aside any enemy fleets, then perform a few general orbital bombardments to wipe out any resource or construction facilities. On the one hand any planets that didn't hate you beforehand will certainly do so after; on the other, a destructive rampage like this is very difficult to stop if you don't have a good fleet in the vicinity, and cleaning up the mess afterwards can take hundreds of in-game days.
** Oh it's better then that. A sufficiently power fleet can just continue to General bombard until the planet's energy resource is completely destroyed preventing ANY buildings from ever being built there again. It's a legit alternative that if the rebels already fully control a sector to just burn every planet to the ground rather then bothering to try and win them over, and unlike the Death Star planet destruction, the negatives from slagging a planet only affect that system.
* ShameIfSomethingHappened: Implied with the Death Star. Merely having it in the vicinity of an occupied planet reduces garrison requirements for the Empire and can even halt uprisings-in-progress due to how terrified the civilians are that you might actually use it.
* ShoutOut: We find a star system by the name of [[Creator/NeilGaiman Neelgaimon]].
* TooAwesomeToUse: The Death Star again. It's essentially the most powerful unit in the game, but is highly vulnerable to trench runs from starfighters, sabotage (if you did not bother putting troops in it), and the fact that using its superlaser on planets costs you dearly in popularity points for your AllianceMeter.
* TorchesAndPitchforks: The enemy can incite uprising on your planets by using infiltrators (or, alternatively, you can do it yourself by blowing up civilian facilities, making unpopular decisions, or losing battles in the area and not stationing enough troops on the planet to keep a lid on things). Uprisings are tremendously destructive - all resource gathering and construction halts, the garrison requirements to quell the uprising are enormous (up to 12 for a single planet), your popularity around the sector drops, and anything on the planet is at risk of being destroyed.
* WeaksauceWeakness: Death Stars are always vulnerable to a trench run by Rebel starfighters, as in the original film. Unlike the later films, where the Second Death Star was going to have that design flaw corrected if it had ever been completed.
* WrongGenreSavvy: No doubt many first-time players thought invading enemy planets was the best way to win the game. In reality, conquering enemy planets through Planetary Assault is at best inefficient, and at worst counterproductive. In fact, it is possible to win the game without conducting a single Planetary Assault.
** To elaborate on why Planetary Assault should be avoided: First of all, your fleet needs to be carrying troop regiments, which of course requires your fleet to have capacity for said troop regiments. Then after your invasion succeeds, you need to leave behind up to six of those regiments to prevent the planet from going into uprising or outright going back to the enemy. Since fleets have limited troop capacity this can quickly eat up your resources, and bringing in more troops takes time. Then you need to invest in some shield generators for the conquered planet; if you don't, an enemy fleet can swoop in and liberate the planet through Planetary Bombardment, which not only destroys your troops and gives the planet back to the enemy but also boosts the enemy's sector-wide loyalty. So to recap: Troops lost, Planet lost, Loyalty lost. Bottom line: use invasions sparingly.
* YouHaveFailedMe: [[spoiler: To the player, if he commands the Empire and loses the game. IMP-22 orders that you be 'sanctioned' for your failure, but seeing as the place is getting blown to pieces by three Mon Calamari Cruisers at the time, he decides to slip away and 'leave the Rebels to apply the appropriate sanctions'. Your command center explodes into flames a few seconds later.]]
** It's also the reason Emperor Palpatine gives for any mission he's on that doesn't go well..."''You have not adequately supported me on this mission...and it has failed.''"