Land warfare

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This article is for the PC version of Stellaris only.

Wars are not decided only in space. In order to capture enemy planets, entire armies are needed, along with the preparation and battlefield awareness to properly use them. However, planets may only be invaded if the system's starbase has been occupied.


Although secondary to space battles, ground warfare is a vital aspect of many wars.

Ground combat takes place between the planet owner's armies and the invader's armies. The number of armies that can be engaged in combat on either side is five plus one-fifth of the Planet Size.png planet size. Excess armies are initially placed in a reserve area behind the frontline and replace any disengaged or destroyed armies as combat progresses.

Each day, each army engaged in combat deals its health and morale damage to a randomly selected enemy army; armies with less than 50% health are twice as likely to be selected. Armies below 50% health may also disengage from battle; this moves them from the frontline area to the reserve area. Disengaged armies cannot return to the frontline but can still be attacked by enemy armies and destroyed. Disengaged armies are half as likely to be selected as the target of an enemy army. Whenever an army is destroyed, there is a 5% chance for the general leading that army to be killed as well.

Unless an army is immune to morale damage, when its morale drops below certain thresholds, the army will be negatively affected with the following modifiers:

Morale Perc. Penalty
50% < Mod army damage mult.png −25% Army damage
0% Mod army damage mult.png −75% Army damage

After 30 days, the attacker can choose to retreat at any time. However, there is a chance that each retreating army is destroyed while attempting to return to space, with the chance increasing as the army is more damaged. This makes retreating a risky endeavor and something to do only in very poorly chosen engagements.

As long as the ground combat is ongoing, it is possible for either side to land reinforcements, though typically this will only be feasible for the attacker. The ground combat ends when the attacker retreats or all armies of either side are destroyed.

Army rank

Rank Exp Points Effects
Regular 0 - 100 None
Experienced 100 - 1000 Mod army damage mult.png +10% Damage
Mod army morale.png +10% Morale
Veteran 1000 - 10000 Mod army damage mult.png +20% Damage
Mod army morale.png +20% Morale
Mod army health.png +10% Health
Elite ≥ 10000 Mod army damage mult.png +40% Damage
Mod army morale.png +40% Morale
Mod army health.png +20% Health

As armies fight battles, they will increase in rank, improving their stats based on their experience points. Armies get +2 experience points each time they deal damage and +1 when they take damage. Army starting experience can be increased by +100 by each of the following:

  • Civic strength of legions.png Strength of Legions civic
  • Civic private military companies.png Private Military Companies civic
  • Military Academy Military Academy building
  • Dread Encampment Dread Encampment building
  • Mercenary Liaison Office Mercenary Liaison Office Corporate holding
  • Pirate Free Haven Pirate Free Haven Corporate holding

Army stat modifiers

In addition to army rank, several technologies, civics, species and leader traits, and other sources affect army damage, health, and other stats. Additionally, General.png generals provide Mod army damage mult.png +5% army damage per level and plus other bonuses from traits. Modifiers from species traits affect armies recruited from that species, while General.png general and Governor.png governor traits affect armies led by that general or on planets in that governor's sector.

Source Mod army health.png Army Health
Trait lithoid.png Lithoid species trait +50%
Trait clone soldier ascendant.png Clone Soldier Ascendant species trait +25%
Tech global defense grid.png Global Defense Grid technology
(Defense armies only)
Resistance is Frugal Resistance is Frugal tradition
(Defense armies only)
Tech repeatable improved army health.png Nerve Dampeners technology +10%

Defense armies

Defense armies are automatically recruited by certain jobs, based on the species working that job, and can be organic or robotic. Defense armies cannot be moved from the colony they are recruited on and are used only to defend against enemy armies. While they are stronger one-for-one than assault armies and their loss does not cause Mod country war exhaustion.png war exhaustion, their limited recruitment means that significant investment is necessary to fend off a concentrated attack.

The type of army recruited depends on the pop working the building that spawns them. Defense armies do not incur any upkeep beyond that of the building and pop which creates the army. Defense armies do not cause collateral damage.

Type Mod army damage mult.png Base Damage Morale Damage Mod army health.png Health Mod army morale.png Morale Source
Army defense.png Defense Army 2.25 - 4.50 2.25 - 4.50 250 250 Organic Job colonist.png+1 Job enforcer.png+2 Job patrol drone.png+2 Job soldier.png+3
Army defense m.png Robotic Defense Army 1.50 - 3.00 1.50 - 3.00 250 Immune Trait mechanical.png Robot Job colonist.png+1 Job enforcer.png+2 Job patrol drone.png+2 Job soldier.png+3
Army undead.png Undead Defense Army 2.25 - 4.50 3.93 - 7.87 350 Immune Organic Job colonist.png+1 Job enforcer.png+2 Job patrol drone.png+2 Job soldier.png+3 Job necromancer.png+3
Replaces normal organic defense armies if at least one Job necromancer.png necromancer is present
Army xenomorph.png Offspring-Led Army 2.62 - 5.25 3.41 - 6.82 400 Immune Origins progenitor hive.png Progenitor Hive Job patrol drone.png+2 Job soldier.png+3
Replaces normal organic defense armies if at least one Job spawning drone.png Offspring Drone is present
Army defense m.png Drone Grid 1.65 - 3.30 1.65 - 3.30 220 Immune Machine unit.png Machine Unit Job patrol drone.png+2 Job soldier.png+3
Event spawned defense armies
Army defense m.png Sentinels 6.00 - 12.00 30.00 - 60.00 1400 Immune Archaeology map icon.png Archaeology site event outcome
Army undead.png Crystalline Bane 52.50 - 105.00 2625.00 - 5250.00 11000 Immune Unexpected Mineral Seams

Assault armies

An empire can recruit assault armies from a colony based on the species living there. The species must not have Military Service Exempt Military Service rights in order to recruit an army from that species. An empire cannot recruit more assault armies from a species than the total number of pops of that species living in the empire, with the exception of Army clone.png Clone Armies. Armies not tied to a species, such as the Army xenomorph.png Xenomorph Army, are unlimited unless otherwise specified.

Unlike defense armies, assault armies are based primarily in space and each recruited army boards a transport ship. Transport ships are unarmed but automatically upgraded with the latest defense and utility components. Assault armies can also be ordered to land on any controlled planet to provide additional defense against invasion.

Type Cost Time Time Energy.png Upkeep Mod army damage mult.png Base Damage Morale Damage Devastation.png Collateral Damage Mod army health.png Health Mod army morale.png Morale Mod country war exhaustion.png War exhaustion Requirements Species
Army assault.png Assault Army Minerals.png 100 90 1 1.50 - 3.00 1.50 - 3.00 100% 200 200 100% Biological
Army slave.png Slave Army Minerals.png 50 60 0.5 1.50 - 3.00 1.12 - 2.25 150% 200 150 50% Slave Processing Facility Slave Processing Facility Biological (enslaved)
Army clone.png Clone Army Minerals.png 75 30 0.75 1.50 - 3.00 1.50 - 3.00 125% 200 200 50% Tech gene banks.png Gene Banks Biological
Army robotic.png Robotic Assault Army Minerals.png 150 90 1.5 1.50 - 3.00 1.50 - 3.00 150% 400 Immune 50% Droids Droids
Menu icon policies.png Robotic Workers Allowed
Army psionic.png Psionic Army Minerals.png 250 120 2.5 3.00 - 6.00 4.50 - 9.00 50% 350 500 300% Tech telepathy.png Telepathy Biological (psionic with Utopia)
Army xenomorph.png Xenomorph Army Minerals.png 200 100 2 3.00 - 6.00 6.00 - 12.00 500% 400 Immune 25% Tech morphogenetic field mastery.png Morphogenetic Field Mastery None
Army gene warrior.png Gene Warrior Army Minerals.png 300 150 3 3.00 - 6.00 3.00 - 6.00 75% 500 500 300% Tech gene seed purification.png Gene Seed Purification Biological
Army undead.png Undead Army Energy.png 100 60 0.75 1.50 - 3.00 2.40 - 4.80 125% 200 Immune 50% Job necromancer.png Necromancer jobs Biological
Army assault m.png Hunter-Killer Army Minerals.png 100 90 1 1.50 - 3.00 1.50 - 3.00 200% 200 Immune 50% Auth machine intelligence.png Machine Intelligence Robot
Army assault m.png Battle Frame Army Minerals.png 200 120 2 2.25 - 4.50 3.00 - 6.00 200% 500 Immune 100% Auth machine intelligence.png Machine Intelligence
Tech adaptive combat algorithms.png Adaptive Combat Algorithms
Army assault m.png Mega-Warform Minerals.png 800 500 8 6.00 - 12.00 9.00 - 18.00 400% 1200 Immune 400% Auth machine intelligence.png Machine Intelligence
Tech biomechanics.png Biomechanics
Army assault m.png Cybrex Warform Alloys.png 250 500 8 7.50 - 15.00 15.00 - 30.00 500% 1400 Immune 400% R war forge.png Cybrex War Forge relic
Can only be recruited on the capital
Army xenomorph.png Titanic Beast Minerals.png 300 90 1 4.50 - 9.00 9.00 - 18.00 300% 1000 600 200% Titanic Lifeforms event chain
Only 3 can be recruited
Army xenomorph.png Azizian Army Minerals.png 250
Energy.png 50
90 1 4.50 - 9.00 9.00 - 18.00 100% 1000 400 100% Ice Alien event chain
Only 3 can be recruited
Army imperial legion.png Imperial Legion Minerals.png 300 150 3 3.75 - 7.50 3.75 - 7.50 75% 600 600 300% GalacticEmpire mainButton.png Galactic Emperor
Resolution imperial institutions.png Imperial Legions resolution
Only 12 can be recruited
Army assault.png Mercenary Army Energy.png 120 0 2 1.65 - 3.30 1.65 - 3.30 250% 200 100 50% Overlord Mercenary enclave deal Biological
Army assault.png Mechanized Mercenary Army Energy.png 240 0 5 3.3 - 6.6 3.3 - 6.6 300% 360 200 50% Overlord Mercenary enclave deal Biological
Army psionic.png Psionic Avatar Event 0 0 7.50 - 15.00 15.00 - 30.00 100% 1400 Immune 500% Utopia.png Shroud event None
Army assault m.png Nanite Warform Event 0 0 15.00 - 30.00 90.00 - 180.00 500% 3600 Immune 400% Distant Stars.png A Quiet Stroll event None
Army undead.png Skeletal Giant Event 0 1.5 4.50 - 9.00 13.50 - 18.00 350% 1400 Immune 50% Civic reanimated armies.png Reanimators
Strange Mountain Formation anomaly

Orbital bombardment

Orbital bombardment occurs when a fleet is in orbit around a hostile colony and is generally a precursor to invasion. Genocidal empires can even opt to skip the invasion entirely and simply exterminate all life on the colony. Orbital bombardment causes damage to any armies as well as Devastation.png devastation. Effectiveness is based on the Fleet Size of the fleet in orbit, where maximum effectiveness is reached at 200 or larger Fleet Size. Assault armies take 5 times more damage from orbital bombardment than defense armies.

Stance Planet damage Army damage Pop kill chance Other effects Requirements
Bombardment light.png Selective 50% 100% 25%
  • Does not kill the last 21 Pops
  • Does not bomb planets with no armies on it
Bombardment limited.png Indiscriminate 100% 150% 50%
  • Does not kill the last 11 Pops
No.pngPacifist.pngFanatic Pacifist.png Not Pacifist
Bombardment armageddon.png Armageddon 150% 200% 100%
  • If the last pop is killed, the planet becomes a Planet nuked.png Tomb World
Any of:
  • Civic fanatic purifiers.png Fanatic Purifiers
  • Civic machine terminator.png Determined Exterminator
  • Become the Crisis Become the Crisis
Bombardment full.png Javorian Pox 20% 150% 150%
  • Does not kill Trait mechanical.png Mechanical Pops
  • If the last pop is killed, the planet becomes a Planet nuked.png Tomb World
  • R pox sample.png Javorian Pox Sample relic activation
  • No.pngPacifist.pngFanatic Pacifist.png Not Pacifist
Raiding bombardment.png Raiding 100% 50% 100%
  • Abducts pops instead of killing them
  • Species with Displacement, Neutering or Extermination species rights will still be killed
  • Does not cause Terror Bombing opinion if successfully abducted
  • Does not kill or abduct the last Pop
  • Civic barbaric despoilers.png Barbaric Despoilers
  • Ap nihilistic acquisition.png Nihilistic Acquisition

Orbital Bombardment Damage dealt to enemy planets can be increased by the following:

Source Mod ship orbital bombardment mult.png Damage
Overwhelming Force Overwhelming Force tradition +20%
Ship part orbital trash dispersal.png Orbital Trash Disperser component +25%
Ship part aura bombardment.png Munitions Plant juggernaut aura +30%
Peril Crisis level 3 +20%

Orbital Bombardment Damage taken from enemy fleets can be reduced by the following:

Source Mod ship orbital bombardment mult.png Damage
Origins subterranean.png Subterranean origin −75%
Planetary Shield Generator Planetary Shield Generator building −50%
Survival Fittest Survival of the Fittest tradition −25%
Never Surrender Never Surrender tradition −25%
Colony type picker.png Fortress World designation −10%
Colony type picker.png Fortress Station designation −10%


Devastation.png Devastation Orbital Bombardment FTL magnet.png FTL inhibitors D huge tree.png Tree of Life Time To


Damage Damage to armies Job purge.png Kills pops
0%-24.9% 50% No.png Functional Alive 498
25%-49.9% 100% Yes.png Functional Alive 998
50%-74.9% 100% Yes.png Disabled Destroyed 1498
75%-100% 200% Yes.png Disabled Destroyed 2000

Devastation is a measure of how much damage has been caused to the colony's infrastructure. It goes from 0 to 100%, and every 1% devastation causes a 1% decrease in Housing.png housing, Amenities.png amenities, Trade value.png trade value, Mod pop resource output.png resources from jobs, Upkeep upkeep from Jobs, Mod pop growth speed.png growth speed and Immigration pull immigration pull.

Devastation is primarily caused by orbital bombardment, and to a lesser degree assault armies. Assault armies have a Collateral Damage modifier that determines how fast they cause devastation. Defense armies do not cause any devastation.

Devastation decreases by 0.05% daily if the colony is not being invaded or bombarded.


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