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Ground combat

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Warning: Obsolete Information
This page concerns the VB6 version of the game (last released December 27, 2015). It has been superseded by a version written in C#, referred to as Aurora C# or C# Aurora, which can be found on the community forums or the main page of this wiki. The latest version of Aurora is 2.1.1 C#. Some information may still be accurate, but use it at your own risk.

You may be able to find current information at CS Aurora:Ground combat.

Ground combat refers to combat operations conducted by or against ground forces. Such operations may involve ship boarding or troop deployment to the surfaces of planets in order to take control. Planetary bombardment can also be employed to reduce local ground forces defenses.

Planetary assaults

Orbiting spacecraft are able to target and destroy ground forces that are not within a PDC. So why have ground forces then? Because PDC designers are likely to give their PDCs very thick armour that in many cases will be able to resist everything that orbiting spacecraft can throw at it, while the PDC proceeds to blast those spacecraft out of the sky. However, PDC weapons are designed to engage spacecraft, not ground forces, so you will be able to use ground forces to assault and capture enemy PDCs. Any ground forces based within the PDC will be able to resist that attack with a considerable defensive bonus. A planetary assault under these circumstances will likely consist of fast spacecraft dashing in to drop troops while under fire from PDCs and then getting the hell out while the ground forces try and take out the PDCs. Attacking ground forces will have the option to concentrate their efforts on a specific PDC (based on sensor contacts) or fight a general action against enemy ground forces outside PDCs (if there are any).

Once hostile ground forces have been eliminated, either through ground combat or orbital bombardment, ground troops will be also needed to force a surrender through occupation.

Troop Transport Modules

All GCU are the same size (except Engineer Brigades, which need five Transport modules in the same ship). A ship needs one Troop Transport module to transport each GCU. GCU may only be moved from a ship to a planet, or vice versa, if the ship is in orbit.

Note that for transport bays, the same rules for loading and unloading apply as for cargo holds, i.e. without a spaceport or cargo handling system, it might take your brigade two weeks to disembark on a hostile planet. That might do if the planet is not defended, but you'd better research combat drop technology if it is.

Combat Drops

Infantry loaded into drop pods can be combat dropped, which doesn't require any unloading time for them to hit the ground and begin fighting. There are battalion-sized and company-sized drop modules (for Marines), which have to be researched first.

You don't need troop bays, but troops held in drop modules will lose morale over time. So you'll want to move them around in troop bays and only transfer them to drop modules when you need to. Don't forget to include Cargo Handling Systems on the transports because troops begin to lose morale as soon as the transfer to drop modules begins. Note that a battalion-sized drop module fits nicely in a FAC.

Cryogenic Combat Drop Modules are drop pods which do not result in a morale loss if troops are kept in them. You cannot mix cryogenic and non-cryogenic drop modules.

How To Combat Drop

1) Go to the F12 task group screen, select a Ship with Combat Drop Modules, click load GU into Drop Module in fleet. You should see a selection of units to load into the unit right below the Plotted Move screen called "Select Ground Unit" appear. Select one and hit Add Move. 2) Advance time till this is complete (takes time to load GUs into the drop pods but they exit the drop pods instantly). 3) Your unit should now be loaded onto a Combat module. 4) Now when you get near a planet or ship, you can select an action for this ship called Combat Drop Ground Unit, or Boarding Action.


Any race with GCU on a planet can choose to attack ground units or PDCs of another race on the same planet. Note that attacking and defending are two different actions so the attacked race may decide to remain on the defensive and not counter-attack. If both sides attack each other, two separate combats are calculated. As the combat is potentially covering the entire planet, each combat round takes place during the five day increment . If time is advanced by more than five days, one combat round takes place for every five days in the increment.

Vs. PDCs

Attacking ground forces will have the option to concentrate their efforts on a specific PDC (based on sensor contacts) or fight a general action against enemy ground forces outside PDCs (if there are any). This is accomplished by choosing which PDC or Population to attack on the Ground Units tab of the Economics window. If a PDC is under attack, only the defenders of that specific PDC are able to take part in the defensive battle. However, troops can emerge from other PDCs to fight an offensive action against the attackers in the field and try to destroy them. Obviously this won't be a good idea if there are enemy spacecraft within weapon range. If the attackers are concentrating on a specific PDC, the defenders are able to move around between other PDCs but are not able to reinforce a PDC under attack. In addition, the PDC under attack may not reload its magazines from the planetary stockpile.

If a PDC is captured (i.e. all ground forces within it are eliminated), it becomes part of the attacking player?s forces. He can move troops in to garrison it and the defenders may try to recapture it. There may be a chance the defender will attempt to blow up the PDC or damage its systems before it is captured, depending on his racial characteristics.

Note that Combat Engineers get a 100% attack and defend bonus in combat vs. PDCs.


Each GCU starts with a Morale of 100. As long as its morale stays at this level it has no effect on combat. If the morale is increased or decreased, it affects both the attack and defense strengths of the unit. The modifier is equal to Strength x (Morale/100). For example, a unit with 110 Morale would have attack and defense strengths 10 percent higher than normal. A unit with 80 Morale would have attack and defense strengths 20 percent less than normal. In addition, when the roll is made after combat to determine if a unit is lost, the chance of being destroyed is divided by the unit?s Morale/100. For example, if a unit with 120 Morale has a fifteen percent chance to be destroyed, the modified chance = 15% / (120/100) = 12.5%, so this unit has now only a 12.5% chance of being destroyed. This simulates that lower morale units are more likely to be destroyed than higher morale units.

Also note transferring units from one Brigade HQ to another has a devastating effect on morale (morale is cut in half). Morale will slowly return to 100 over a period of weeks to months assuming the unit is on a olony and not in combat.


Ground Forces Officers may be assigned to command ground units (Leaders window, Leader Type->Ground Forces Officers). Leaders must be of rank 2 to command brigade headquarters (HQs) and rank 3 to command division HQs.

Ground Combat Bonus:

An officer's Ground Combat Bonus improves the attack and defence strengths of the unit (s)he commands and all subordinate units. This bonus is always applied fully; a divisional commander applies his full bonus to all units in the division. Ground Combat Bonuses stack, and so a unit subordinate to both a division and brigade commander can get bonuses from its own officer (at 100%), the brigade commander (100%), and the division commander (100%). Additional bonuses are detailed below.

Units in a brigade (including the brigade HQ) subordinate to a division HQ get an additional combat bonus (in %) equal to the product of the combat bonuses (again, in %) of both division and brigade leaders, divided by 100. Therefore, units commanded by a divisional commander with a bonus of 20% and a brigade commander with a bonus of 10% will get a 20% + 10% + (20%*10%/100 = 2%) = 32% bonus.

Units commanded by three officers - divisional commander, brigade commander, and individual unit leader - get an additional bonus approximately equal to 30%-60% (depending on divisional and brigade commander bonuses) of the unit leader's bonus.

Ground Forces Training Rating

The morale of ground units may increase over time, based on the Ground Forces Training Rating of their brigade and division commanders.

Every non-HQ unit is checked every 5-day increment. Those that have at least 100 morale (i.e. have fully recovered from combat) and are on the same planet as their Brigade Headquarters have a chance of morale increase. The base annual chance of increase is equal to the Ground Forces Training Rating of the Brigade commander. If the parent Division HQ of the Brigade HQ is also on the same planet, half the Ground Forces Training Rating of the Division commander is added to the chance of increase. If the Morale of the ground unit is above 100, the chance of morale increase is reduced by double the amount of morale exceeding 100.

This does not applies to battalions, Brigade HQs and Division HQs that are on board ships or in PDCs. So a battalion in a PDC cannot gain morale from training and a battalion on a planetary surface outside a PDC cannot gain morale from training if the Brigade HQ is on a ship or in a PDC. -- Steve Walmsley, from post,2308.0.html


If all PDCs and defending ground units are eliminated, the attacking player may be in a position to conquer and occupy the defending population. The required garrison strength is based on the defence strength of the occupying force. The garrison strength required to force a surrender is equal to: Pop in millions * Racial Determination/100 * Racial Militancy/100

For example, if the defenders have a population of 400m, a Determination of 60 and a Militancy of 50, the required garrison strength will be: 400 * (60/100) * (50/100) = 120. Note that this is a minimum amount required to force a surrender. It may be desirable to station a larger force on the planet to avoid disruption to its production facilities.

When a population is conquered, there is a chance some tech will be recovered by the occupying forces. A check is made against every background tech known by the conquered race but not the conquering race. The percentage chance of learning each tech is equal to Pop in million/5. For example, conquering a pop of 200m will yield a 40% chance of learning each background tech known by the conquered race.

Boarding and capturing ships

Ships designed with Combat Drop Modules can attempt to board and capture other ships or stations. If successfully boarded, the defending ship crew and any ground troop detachment on board will attempt to repel the boarding party.


Boarding is a complex and risky operation, usually attempted only against disabled or slow-moving ships. When the fleet intercepts the target, a boarding attempt is carried out. Actually docking with a target that is evading is virtually impossible so the assault involves using a combat drop module to fire the troopers at the enemy ship. They land on the hull, lock themselves in place and either enter through holes in the armour or blast their way in. Once the boarding units have gained access to the hostile ship interior, combat takes place between the boarders and the crew of the hostile ship plus any hostile ground units on board.

Trying to board a ship moving at several hundred or several thousand kilometers per second in this manner is still incredibly risky. Because of the speeds involved, the intercepting vessel must have a huge speed advantage to make the boarding attempt without suffering heavy casualties among the boarders. The cause of those casualties will vary but could include missing the target and ending up within the exhaust plume, impacting the hull at too high a speed, missing entirely and being lost in space, etc. The percentage of casualties from the boarding attempt is equal to 20xD10, giving a range from 20-200%. However, the amount of D10 rolled is reduced by Interception Speed / Target Speed. For example, if the interception speed is 6000 km/s and the target is moving at 1000 km/s, the number of D10 is reduced by 6. Therefore, if the intercepting ship is at least twenty times faster than the target ship, the attempt is automatically successful and no casualties are suffered during the boarding. Because of the risks involved, in most cases before a boarding attempt can be made the target ship will have to be slowed down or disabled.

Once the boarding units land on the enemy ship, they will attempt to enter. If the armour has already been penetrated by weapon fire, they will enter through the damaged section. If the armour is intact or the damage does not penetrate to the interior they will begin using breaching charges to gain access. One breaching charge will be detonated every thirty seconds and will destroy one point of armour. The boarding units will always chose the point at which the armour is most damaged to place the breaching charge. They should gain access to most ships fairly quickly, especially if the ship has already been slowed down by damage. It may take longer to blast into well-protected PDCs.


Once the boarding units have gained access to the hostile ship interior, combat takes place between the boarders and the crew of the hostile ship plus any hostile ground units on board. The crew will not be as effective as dedicated combat troops but they are still military personnel with at least some basic combat training and they will be familiar with the layout of their ship. Therefore the combat strength of the crew is equal to 1 defence point for every 100 crew.

As this is a high intensity, close quarters engagement it is resolved much more quickly than ground combat. Combat is calculated using the same formula as ground combat with the following exceptions:

  1. Combat takes place every five minutes after movement and combat. Once a unit has successfully boarded a hostile vessel, the Boarding Combat Clock begins counting. Once it reaches 300 seconds or greater, a round of boarding combat is fought and the clock is reduced by 300.
  2. Low readiness units on both sides cannot avoid combat
  3. The boarders cannot retreat so they must keep attacking until they capture the ship, die trying or surrender.
  4. As a result of the boarding combat, collateral damage may be inflicted to the ship itself. If this is severe enough, or causes secondary explosions, it is possible the ship might blow up in the midst of the fight.
  5. If all the defending units and crew are eliminated, the ship is captured.

How To Use

  1. First you need a much faster ship than the ship you plan to try to take over. This is achieved via the small Drop Module and a fighter with an engine and a little bit of fuel and a tiny engineering section.
  2. Load Ground Force Unit into Drop Modules within fleet (if fighter is in a fleet). Then select an enemy ship and issue a boarding order.
  3. The Troop Shuttle will carry the troops from the fleet over to the enemy vessel and barring any accidents like the enemy blowing a 80cm hole in the troop ship you are all set for the shuttle to launch its troops at the enemy vessel and begin boarding actions.
  4. The faster your Troop Shuttle is, the better the chance that more Marines will land on the enemy ship and giving you a better chance to take it over successfully.


  • Dropping or unloading troops on an enemy-held planet creates a new colony. If you fight and win, there will still be two separate colonies - one where you unloaded your forces, and the one you just conquered. Use the Ground Units tab in the Population and Production window to transfer your forces, or have them board a transport again, wait till they are aboard and then abandon the empty colony.
  • See also Ground Forces: Transportation, New units, Boarding Combat, Steve Walmsley dev "diary", 2009.