How To Conquer Other Civilizations – Stellaris Beginners Guide
How To Conquer Other Civilizations – Stellaris Beginners Guide
If you’re coming from other 4x games (e.g. Civ, MoO, Endless Space, etc), you’ll find that the process of absorbing other empires through military conflict is a bit more nuanced in Stellaris. This is a quick guide on the various strategies that I wish I knew at the start of Stellaris. The advantage of a hostile takeover versus a fresh colony is that you get to keep the buildings, saving you tons of cash.
PURGE – The following strategies require either collectivist or xenophobia empire ethos. It is not compatible with xenophilia or individualistic empires.
Resettlement (Best with Collectivism) At the start of a war, your war goals should be to CEDE PLANET. The planet should have higher than 5 population for this to work. You also need to have a core system and the RESETTLEMENT policy enabled. After the war is won, you need to check to see if there is a Planetary Administration or above on the planet. If there is not, you need to upgrade the Reassembled Ship Shelter to a Planetary Administration. After this is done, make sure there is one empty tile. If there is not, purge ONE population and babysit the planet until the population disappears. Then go to one of your core worlds, and resettle one population over. Then purge all the filthy aliens on the planet. Your own people will repopulate the planet over time. You can resettle more than one colonist if you are swimming in Influence.
 If the habitat of the planet is not well-suited to your own race’s habitability, you need to have the GENE TAILORING technology (Genome Mapping -> Epigenetic Triggers -> Gene Tailoring). Go immediately to the species screen, select your race, find the planet and reengineer the resettled colonist to the planet’s native habitat. Remember to hit F5 and research the special project after you gene tailored it.
Migration (Best with Xenophobia and Individualism. Doesn’t mix well with spiritualism) At the start of the war, your war goals should be to CEDE PLANET. You need to have FREE MIGRATION turned on, and you need to have at least a ROBOT researched (Powered Exoskeletons -> Robotic Workers). You also need planets in your empire with pops suited to the habitat (see  on how to re-engineer your species). After the war is won, make sure there is one empty tile. If there is not, purge ONE population and babysit the planet until the population disappears. Build one robot on a food or mineral tile. You can purge all the filthy aliens immediately as the robot is being constructed. Enact the Land of Opportunity edict after the aliens burn in the ovens and your people should migrate over time to keep your lonely robot company.
Synthetic Takeover (Best with Materialistic) You need to have synthetics researched. At the start of the war your goals should be to CEDE PLANET. After the war is won, make sure there is one empty tile. If there is not, purge ONE population and babysit the planet until the population disappears. Build one synthetic population in the free tile. You can now purge all the filthy aliens. Queue up the rest of the planet with Synthetic droids (don’t forget the hotkey B on a tile). Congrats, you just replaced an entire planet with synths while the Institute struggles to replace the Boston Commonwealth.
Clean Slate Again your war goals should be to CEDE PLANET. Making them abandon planet will save you one step, but there can be bad side effects to border transfer. When the war is one, purge everything, then hit the planet with a fresh colony ship. If the planet is not suited for your people, see  above.
RELIGIOUS CONVERSION – Best suited for -%ethics divergence ethos and governments, namely Spiritualism in 1.2. Collectivism also helps. Xenophobic empires will get a small happiness penalty with the result
The advantage to this method is that you can get partial production from the planet right away, and you don’t have to wait for the planet to regrow itself from a purge. Another advantage is that you don’t need gene tailoring for this to work. So if the alien race is in a drastically different climate than your own race, you can use the aliens to settle new worlds of that climate type– after you indoctrinated them.
Things that help: Fanatic spiritualist (-30% divergence), spiritualist (-10% divergence), divine mandate (-10% divergence), transcendent empire (-20% divergence).
If you have collectivist as well, you can build a -15% divergence empire-wide building with Ministry of Benevolence (Galactic Administration->Galactic Benevolence).
Also as collectivist, you can research Frontier Commissars for -20% ethics divergence empire wide. Hattip To get this you need (New Worlds Protocol -> Frontier Collectives -> Frontier Commissars). Note that this is a rare technology that is nearly impossible to get unless you have a scientist with the New Worlds trait.
You can also build a orbital mind control laser for -30% divergence. To do this you need the technology Will To Power (Aritificial Moral Codes-> Synthetic Thought Patterns-> Will to Power). This is a rare technology that is hard to get if you are not collectivist. You have the best chance to get this if you are using a scientist that is maniacal.
If you are a divine mandate/transcendent empire you can build a -10% divergence grand mausoleum per ruler.
If you are spiritualist/fanatic spiritualist you can build a -10% divergence monument building.
If you are militaristic/fanatic militarist, you can build a Virtual combat arena that gives -5% divergence and +5% happiness.
There is also an empire-wide edict that decreases divergence, but it slows down your research too so I never use it.
Good empire-wide happiness also helps indirectly, but not as big as ethics divergence.
Your war goals should be to CEDE PLANET. After the war is won, activate the edict REEDUCATION CAMPAIGNS. Build a spaceport and activate a mind control laser. If you have empty spaces, build those -X% divergence buildings. When the heathen population has been successfully indoctrinated into your empire’s ethos, you can replace the mind control laser at your Spaceport with something else by clicking on the module.
POLITICAL INTEGRATION – This works best with Fanatic Xenophile/Xenophile empires because of the reduced influence cost and diplomatic bonuses. Charismatic leaders also help.
At the start of the war your goals should be to LIBERATE PLANET. After the war is won, a splinter empire will be created that will mirror your ethos. Note that the pops in the planets will not yet have their ethos changed, it will happen over time. Contact the splinter empire and demand them to be your vassal. Your empire needs to be much stronger than them for this to work. After they are your vassal you can demand that they integrate into your empire. You must maintain good diplomatic standings during this entire process. You must also defend this empire while they are in a vulnerable state.
Note that this method is much much slower than the other methods, and it costs a huge amount of influencce points. The small advantage of this method is that you don’t get the increased research cost that comes with planet count / pop count, until you get the entire planet at a time. There is no period where you are waiting for populations to grow with purges or waiting for the Recently Conquered debuff to wear off along with ethics convergence.
SLAVERY – This method requires collectivism or xenophobia.
The advantage of this method compared to purging is that the mineral and food population gets full production efficiency fairly quickly. This method works well with Despotic Empires / Star Empires. The basic setup is similar to the PURGE method. You take over the planet through a war with the CEDE PLANET option. You also migrate one of your own population over, or build a synthetic to serve as their overlords. Somebody’s got to hold the whip. Have your population work the energy and research tiles. Enslave the alien population on food and mineral tiles. You have the option of purging the rest of the alien scum to remind the enslaved aliens that you are in charge and they must work hard if they want to live.
edit: Reminder that if your populations are unemployed on a seemingly developed tile, it could be that the building was damaged during bombing, or deactivated during the siege or political reintegration. Simply repair or reactivate the tile to fix this.