Ground Combat!

[Geoff the Medio]

Edit: I notice now that there already is a ground combat thread. Sorry for the duplication. Perhaps a new thread would be good at this point though, as the old one is 5+ pages long. This way interested parties still around from the old thread can summarize their views / suggestions, saving the need to reread the whole old thread to join the discussion...

Regarding issues discussed in the old thread, the rest of this post deals with a fairly simple and abstracted system of combat, without maps or force placement. Ground combat resolves "instantly" in game-time, and takes place after fleet battles.

This seems like the best way to do ground combat to me. /Edit



Based on the idea / restriction that we will only have a single player race at any time on a planet ( see here viewtopic.php?p=13718#13718 ), I began to wonder how to deal with situations which would arise that would "normally" result in two player races cohabitating a planet. This has lead me to concont a proposal for the design of ground combat, which includes this issue.

As a side note, I should note that this does not deal with the issue of what happens when two empires attempt to simultaneously colonize a planet that is uncolonized at the time. In order to resolve this, I would suggest some sort of "claiming territory" diplomatic option. In the event two empires claim the same territory, they would resolve the dispute diplomatically, or resort to war. In the event two empires attempted to colonize a planet at the same time without claiming it first while they are at peace, that turn's colonization order would be nullified, and they would have to resolve the issue the same way as with conflicting claims. If the colonizing empires were at war, a ground battle would be fought, and the winner would colonize the planet with any remaining colonists after the battle. If all colonists are wiped out in the battle, then nobody colonized the planet that turn.

Now, to the proposal:

There are several classes of ground troops, with differing abilities and functions. They are:

-Colonists: These are the normal, unspecialized, resource producing creatures in your empire. The function as light infantry or militia when their colony is attacked, or they are dropped onto an enemy colony as attackers themselves.

-Marines: These are the simplest type of specialized combat unit. They function as heavy infantry, as well as having a number of useful properties that make them important to have when invading or as defenders on your planets. In particular, they are able to take over control of a colony without first killing all the colonists.

-Infantry Fighting Vehicles: aka "IFVs", these are motorized vehicles designed specifically to kill marines and civilians.

-Armoured Assault Vehicles: aka "tanks", these are great at destroying IFVs and moderately good at killing marines and colonists. They are also the only effective weapon against other tanks.

It is also possible to use your orbitting space ships to bombard the planet, effectively destroying any type of ground troops, as well as damagine the infrastructure and environment of the planet (and likely suffering diplomatic penalties).


Theory of ground wars:

All colonies have a larger number of colonists, and thus a large number of light infantry when attacked. If a planet has no other ground troops, and is attacked by a tarnsport ship dropping nothing but colonists itself, the battle is essentially a giant melee, and whoever has the most troops, after considering combat modifiers (morale, defensive bonus, race of troops involved, environment preferences, etc). The result of this is that one side ends up wiping out all the colonists of the other, and the winning race takes control of the planet, with somewhat reduced numbers itself.

If a planet with nothing but colonists to defend is attacked with marines, it is possible that the marines will take over the planet's government without actually fighting the colonists. The ease with which this can be done depends on a number of factors, such as those listed above for colonist vs colonist battles, marine experience level (colonists have no experience levels) and loyalty and happiness and espionage / propeganda being conducted on the planet by either side (or a third party). Generally, taking over the government of a planet with marines requires a small fraction of the population of the planet in marines, say 1/500. Having fewer marines than this, the government takeover will fail, and the marines will be forced to fight the colonists as if they were light infantry. They will kill many more colonists than there are marines, say 10 or 20 times more, but will likely be wiped out in the process.

If a planet with marines stationed on it is attacked, the defending marines will prevent the attacking marines from taking over the government, as long as some are left. While there are marines defending, the colonists do not get involved in the battle, and the marines fight amongst themselves. When one side's marines are wiped out, either the battle is over, or the attackin marines won, and the situation reverts to the one above.

Infantry Fighting Vehicles are specifically designed to kill marines and colonists. If a planet has IFVs defending, they attack the attacking marines, and wipe them out with great efficiency. Similarly, attacking with IFVs will allow the attacker to kill defending marines before the attacking marines are put at risk. IFVs are not, however able to defend a planet against government takeovers. If a planet has IFVs, colonists, but no marines, then attacking marines can ignore the defending IFVs, and attempt to take over the planet's government without fighting them. If the takeover is successful, the IFVs are either captured or destroyed. If the take over is not successful (based on # of marines, # of colonists and modifiers), then the IFVs engage the marines, and likely wipe them out. If the marines somehow take out the IFVs (weren't many, for instance), then the marines engage the colonists directly. Similarly, if an attack force has only IFVs, then it will be almost completely ineffective against any colony, even one with just colonists, and no marines, IFVs or tanks of its own. IFVs (and tanks) need to be supported with marines or colonists to function. Without one colonists or marines in the battle, IFVs are instantly lost (or perhaps after a single battle round, see below for combat calculations).

If both defender and attack have IFVs, they can also engage eachother directly, in which case the result is similar to marines vs. marines, or colonists vs. colonists.

Armoured Assault Vehicles very effectively kill IFVs. Defending tanks will likely destroy any attacking IFVs, preventing them from hurting the defending marines. Attacking tanks will likely destroy any defending IFVs, and would then attack the marines themselves (though not very effectively), as well as allowing attacking IFVs to engage marines. Attacking tanks can also engage defending tanks, which is again a battle of equals, and decided by numbers and modifiers. After one side runs out of tanks, the other can likely destroy the tankless side's IFVs, meaning the side with tanks can then use marines without far of them being attacked, and such. Like with IFVs, tanks cannot function without marines or colonists to support them. If a defending or attacking army loses all its marines and colonists, then the tanks (and IFVs) in the battle are immediately lost.

Combat Calculations

Combat consists of a series of "rounds", in which the ground armies of either side attack the opposing army, reducing their numbers. Rounds continue to be simualted until one side or the other is defeated (see above). When attacking, each class of ground force in an army that round focuses one class of the opposing army. Thus an army with tanks could focus its tank attack on the opposing tanks, hoping to wipe them out. Each combat round, each troop type of an army can either attack a type of troop in the other army, or withdraw / be defensive that round. Defensive / withdrawn troop types do not attack the opposing army in a round, but can be attacked by one or more of the troop types in the oppisng army.

Each pairing of troop types has base damage rates against all troop types, including itself, in various cases. The cases of damage ratings are:

a) attacking, and being attacked back
b) attacking defensive troop type
c) attacking troop type that is attacking something else
d) defending, and being attacked

Depending on the attack targets / defensive status of the troop types in the battle, the damage ratings are chosen. For example:

(a) would occur if the tanks of both armies attack eachother on the same round. The damage done to the opposing tanks would be a product of the tank (a) rating against tanks, and the numbers of tanks in each army.

(b) and (d) would occur if tanks in army 1 attacked IFVs in army 2, which were defending that round. The damage done to army 2's IFVs would be a product of the number of tanks in army 1 and the tank (b) rating against IFVs. The damage done to army 1's tanks would be a product of the number of IFVs in army 2 and the (d) rating for IFVs being attacked by tanks.

(c) would occur if army 1's tanks attacked army 2's IFVs, and army 2's IFVs were attacking army 1's marines. Army 1's tanks would not be damaged, since army 2's tanks are attacking something else. Army 2's IFVs would receive damage that is a product of the number of tanks in army 1 and the (c) rating for tanks against IFVs. Army 1's marines would receive damage depending on what they were doing that round, be it attacking the IFVs of army 2, defending, or attacking something else, as described above.

All troop types of both armies "attack" their desigated targets simultaneously. Damage done is based on troop numbers at the start of around, and damage is done at the end of the battle round.

If at any time during the battle, one side loses all its marines and colonists, the battle is won by the other side. If the defender loses all his/her marines, then the attacking marines can attempt to take over the government of the planet. If they succeed, the battle ends with the attacker winning and the remaining IFVs and tanks of the defender are destroyed or captured by the attacker. If the marines fail to take over the government, the battle resumes until all attackers or defenders are killed.

A possible quirk might be that changing attack targets requires a round, during which time a troop type is neither defending nor attacking, so receives (large) damage as if it was attacking something other than anything that attacks it that round, and also does no damage to anything that round.

Battle Plans

Since having to specify during a battle what troop types your own troop types should focus on would be tedious and time consuming, specifying this with "battle plans" seems a reasonable way to go. These plans could either be predefined, or customizable with some sort of branching logic. Given the limited number of possibilities however, it might be possible to give the player every possible battle plan, or let the player use an in-game set of options to specify custom battle plans, rather than any sort of branching logic scripting.

Battle plans would primarily consist of an order of priorities for each type of troop, and perhaps when to engage or withdraw from a battle. Thus you'd tell your tanks to focus on killing enemy tanks, then IFVs, then marines. Your marines would be told with stay defensive until the enemy IFVs are gone, then engage enemy marines. Your IFVs would be told to attack marines immediately, or perhaps remain defensive until the enemy tanks are gone. Your colonists could be told to attack marines, tanks or whatever, or remain defensive. A defender using colonists to attack might risk losing signifiant numbers of them in the battle, which they might have won even without using the colonists. The colonists might also turn the tide, and win the battle, saving the empire's control of the planet. Using colonists in a battle would probably be bad for happiness and loyalty, however.

Regarding how this relates to not having multiple races per planet: Essentially, it's an act of war to put colonists on someone else's planet, and they are considered to be attacking troops if you do so, and thus you are in a state of war, and the colonists and troops on the planet can attack the dropped troops. At the end of a battle, if the attackers have colonists, but used marines to take over the palnet, the attacking colonists go back to their transport ships, and aren't allowed to stay on the planet. If, instead, the attackers win, the colonists that were dropped form the population of the new colony.

Also: If anyone can think of some more exotic types of ground troops (or non "ground" troops that aren't space-based) that would add something unique or meaningful to ground battles, I'd like to hear suggestions. Things like atmospheric flying craft, combat engineers, etc. They need to have pros and cons and fit into the scheme sensibly, though.

Also more: "ground" is not meant to imply that ocean planets don't count.

Also even more: There would likely be tech levels of ground troops, as well as morale and race modifiers to combat. So "tank" might mean something like we have today, or it might mean imperial walkers.

[noelte]

ground combat is set to be done in v.6, thats four steps away (say at current speed about a year, at least). Maybe we should focus our energy for now on space combat,ship design, tech tree, ...!?

[Geoff the Medio]

ground combat is set to be done in v.6, thats four steps away (say at current speed about a year, at least). Maybe we should focus our energy for now on space combat,ship design, tech tree, ...!?

Roadmap says, under v0.4 "Ground combat is under discussion", meaning it might get included in v0.4. I also fail to see why all cannot be worked on simultaneously, at least in brainstorming, even if not included until v0.6.

[noelte]

I missed that gc was mentined in v.4, i only looked at the big dots:-)

----

IMO, we shouldn't handle colonist as light infantry or any other combat asset, even if this would be more realistic. Otherwise attacking marines might kill all colonists in order to conquer the planet. That's no fun, because taking over colonist is (make them to slaves).

[Daveybaby]

I agree, colonists should pretty much just be standing there watching the show (aside from 'collateral damage', of course). Conquering a planet shouldnt mean having to fight the general civilian population, you just have to beat the defending military units.

Note : general trend in warfare - as technology becomes more advanced (and thus more complex and expensive) the number of troops required as a percentage of the general population tends to fall. Instead you have fewer, more specialised troops who require extensive training to be able to use their weapons effectively. Average joes dont really have a prayer of inflicting anything other than a mild inconvenience against a proper military force.

Possible Exceptions for consideration:

(1) Militia/Territorials/Reservists : a percentage of your population could be trained in combat (this could be a general government policy - which costs money, but not as much money as training full time troops) as reservists (kinda like national service) and take up arms in the event they are needed. These units would be only be lightly armed - no access to tanks/artillery. Losses in combat would directly affect planetary population, but would NOT result in elimination of population, since its only a relatively small percentage.

(2) Warrior Races : conceivably there may be racial picks to create a warrior race - such a race might choose to fight to the last man/woman/child, making them very difficult to conquer, you would need a lot of troops. Basically this would take the form of a militia, but with all of the population taking up arms. Note that these are still only lightly armed units - for heavy weapons/tanks/artillery you would still need to create/train specialised full time units. Basically we are talking klingons here, i guess.

(3) Popular uprising - conceivably you would need to garrison a recently conquered world to maintain order and ownership. If an insufficient garrison is left on the planet then an uprising of a lightly armed militia (as in (1) above) could cause new ground combats to occur in later turns.

(4) Population fights for its own survival - if you are being attacked by a race whose policy is to exterminate all civilians, then conceivably the entire population would fight. However, unless they are trained then they arent going to do much good as anything but cannon fodder, and chances are the general population still wouldnt fight unless there was no proper military to defend them.

(5) Guerillas/Freedom Fighters/Terrorists (depending on your point of view) - i guess this should be abstracted down to some level of social unrest (although admittedly a pretty high level). These guys are never going to do significant material damage to an occupying armed force, but they can increase unrest (possibly leading to (4) above) damage planetary infrastructure, decrease efficiency/output.



Another issue for consideration : if ground combat doesnt remove the general population from a planet, then how do we achieve that goal if we want to? e.g. to use a Moo3 example, if you conquer a planet of harvesters, then you should be clearing the planet of them, not just leave them there to take over your whole empire - duh

Basically, we are talking about the ugly subject of ethnic cleansing.

(1) Genocide - either as government policy or as a racial characteristic (e.g. moo3's harvesters, or the star trek's borg). Elimination of the target population - or conversion into more of your own race (i.e effectively using them as food)

(2) Forced Repatriation / Refugees - i.e. you force the population back to their home empire's territory. Dunno if this is feasible to simulate - probably not.

[Aquitaine]

Ground combat will almost certainly not be in v0.4. I believe the way we left is that we are planning for it to go in v0.6 unless something happens between now and when we start writing v0.4 to make us reconsider this.

[Geoff the Medio]

I agree, colonists should pretty much just be standing there watching the show (aside from 'collateral damage', of course). Conquering a planet shouldnt mean having to fight the general civilian population, you just have to beat the defending military units.

This was the idea behind having attacking marines take over the government if there are no defending marines. (Optionally IFVs could stop this as well, but not tanks)

However, if two people arrive with transports full of colonists, and they both decide to settle simultaneously, and can't resolve the issue diplomatically, the colonists would fight eachother directly, with the winner settling the planet with the remaining colonists after the battle.

Another issue for consideration : if ground combat doesnt remove the general population from a planet, then how do we achieve that goal if we want to?

Killing colonists would be a possible goal of ground combat. If you would rather exterminate the population than take over the government and keep the population to enslave / employ yourself, then you can do so. (This would also be the situation if you had two colony ships dropping their troops on a planet with no other types of troops.) You could also just drop a bunch of IFVs and marines with the goal of killing civilians, and not even try to take over the government. You can also bombard the planet from orbit to kill colonists (and other ground troops) without bothering to drop your own, though this would be bad diplomatically and would damage the planet, making it less habitable for you after removing the current colonists.

e.g. to use a Moo3 example, if you conquer a planet of harvesters, then you should be clearing the planet of them, not just leave them there to take over your whole empire - duh

I don't know how harvesters work, but if they migrated to your other planets, or killed colonists of other races on their planets, then this isn't an issue, because there's only one player race on a planet, and no migration of one race onto a planet populated by another race. If natives exist, they don't migrate at all. I suppose harvesters could be natives that kill your colonists, in which case you'd probably want to exterminate them, which could be modelled as a ground battle in which you instruct your troops to kill the native civilians. Alternatively, the harvesters would be a rather bad type of natives that renders the planet mostly useless, unless there's some other great resource / special there that make it worth colonizing the planet to access.

[Daveybaby]

However, if two people arrive with transports full of colonists, and they both decide to settle simultaneously, and can't resolve the issue diplomatically, the colonists would fight eachother directly, with the winner settling the planet with the remaining colonists after the battle.

Sounds fair enough - though its probably a rare enough situation that its not worth implementing anything too complex just for that.

Killing colonists would be a possible goal of ground combat.

Of course, the colonists would fight back (pretty ineffectively, but there will be a lot of em) if it was a matter of survival (exception 4 in my previous post).

If you would rather exterminate the population than take over the government...

Thats all lovely, but it brings up a question i've been wrestling with for quite a while now... (also this hopefully drags the topic away from ground combat, since theres not much point in discussing it right now) - is there any way to empty a planet if you already own it? (so you can repopulate it with a more suitable race). e.g. If you own a planet with environment type X with race Y living on it, but race Y can only just survive in that environment (so the population is barely rising, output is poor, etc) is there going to be any way to somehow resettle the planet with race Z (who just LOVE environment X)?

So maybe we need a way to move pop points around as in Moo2 - this should be an expensive undertaking (to discourage people from microing pop too much). Also it should probably cause *massive* unrest in the relocated population (people dont like to be forced to move, even if they are living in a shithole).

I don't know how harvesters work, but if they migrated to your other planets, or killed colonists of other races on their planets, then this isn't an issue, because there's only one player race on a planet, and no migration of one race onto a planet populated by another race.

Heh, dont worry about that - it was just a random rant aimed at Moo3

[Geoff the Medio]

Killing colonists would be a possible goal of ground combat.

Of course, the colonists would fight back (pretty ineffectively, but there will be a lot of em) if it was a matter of survival (exception 4 in my previous post).

I was figuring marines would kill colonists at about 20 to 1, IFVs 40 to 1 and tanks 5 to 1. The marine numbers were based on 500 to 1 being the number of marines typically needed to take over a government, and the other numbers were just made up now.

If you would rather exterminate the population than take over the government...

Thats all lovely, but it brings up a question i've been wrestling with for quite a while now...
...
is there any way to empty a planet if you already own it? ...

If colonists are treated just like other ground troops (except with the nifty ability that they can found new colonies), and can be put into transport ships and dropped off somewhere to start a new colony, or to assualt someone else's colony as light infantry, then you'd just need to load them all into transports and ship them off. You'd need to load them up faster than they reproduce though, so it might help if there were ways to have self-imposed health / growth caps for planets.

[Daveybaby]

I guess i only have a problem with this because, unless youre talking warrior races here, your general population would tell you exactly where to go if you plonked them down on a planet and asked them to assault a batallion of tanks.

Unless, of course, the survival issue of one of the other exceptions i raised pops up.

However i guess you could argue thats an objection due to realism issues and is thus invalid

[Geoff the Medio]

I guess i only have a problem with this because, unless youre talking warrior races here, your general population would tell you exactly where to go if you plonked them down on a planet and asked them to assault a batallion of tanks.

Unless, of course, the survival issue of one of the other exceptions i raised pops up.

Well, I think space exploration and colonization is a rough life, so you have to be willing to accept the risk of being in ground battles (or killed on your transport) if you want to be a colonist. Colonists really are "light infantry"... not just joe and jane settler, and are ready and willing and trained to fight for their lives and the glory of the empire and such.

Perhaps race characteristics and empire government might make colonizing rather difficult. If colonizing is particularily dangerous, you have to get volunteers to do it in a democracy, and most people would rather stay on the relatively safer homeworld, meaning you can't make many colonists, meaning your expansion is very much slowed. A dictatorship / warrior race would be much more keen to sign up and go off to be dropped onto another empire's colony to hack away as some fleshy weaklings of another race for the glory of the empire [/klingon]

[Impaler]

I agree the Regular Colonists should get in the Fight but not nessarily ALL of them. Some should be submisive and basicaly "wait out the battle" they just become subjects/victims of who ever wins.

So we need a means of desiding how many of them Fight and how many Cower. What better means of desiding this then the Loyalty %'s being discussed by Geoff in the "Natives" Thread. All population that is "Anti" to the Attacker/Defender (and atleast Nutral to the other side) becomes "Irregular Fighters" with quality being determined by Race and other factors such as "Goverment Militia Training" or "Smuggled weapons". Nutrals sit out all Battles ofcorse.

By using Politics to deside the amount of Irregular support the player has a great insentive to stire up resistence movments in any territory that has fallen the the Enemy (think French Resistence WWII) prior to launching an attack.


Geoff: In response to that last though on Colonists: I realy like the direction thats going in, how about making "Colonists" a unique thing differnt from both "Soldiars" (high combat power/no productivity) and "Workers/Citizens" (low combat power/high productivity). Colonists would be Medium in Both areas and they have the Unique ability to settle new colonies, they are also the only members of your population that will migrate from place to place. A small % of your population is naturaly "Born" as Colonists and are willing to undergo the dangers of interstellar travel to strange new worlds. And if you need more you can bribe people to go and "Buy" Colonists (many things modify the cost here) or if your a bully you can Forcibly create Colonists (some downside assosiated with that ofcorse). Cost assosiated with Bribing Colonists could be yet another means of limiting Sprawling expantion. Think of normal workers as "Glued down" to the planet they were born on, Colonists are "unattached" and can be moved around as the player sees fit just like in classic Moo games. The seperation here gives a Balance between some of the issues raised for Migration.

[Geoff the Medio]

Some should be submisive and basicaly "wait out the battle" they just become subjects/victims of who ever wins.

Two comments...

First, colonists dropped from transport ships onto a planet to fight should be 100% loyal. Presumably they volunteered or were brainwashed into being colonists / cannon fodder. This seems essential for there to only be 1 race per planet, as otherwise you'd end the battle with some of the attacking race's colonists still alive on a planet after all the fighting ones are dead, meanign the attackers lost. The non-fighting attacker colonists wouldn't be able to join the planet's population, and wouldn't necessarily be able to go back to their transport... (and might not be wanted back, since they refused to fight...). And how to calculate the ratio of attacking colonists that fight would be an issue. Best to avoid it, IMO.

I guess this also means that ground combat would need to be after space combat, for this to work. If you succeeded in taking over a colony with marines, but had colonists in the battle as well, then you'd need to be able to take the colonists back up to the transport ship, so that the one race / planet condition is maintained. If space battles kept going during the ground battle, the transport could be destroyed, creating a problem...

Second, I did suggest before that types of troops, including colonists, could be given different targets in battle, such as a specific type of troop in the enemy army, or "none". If attacking nothing, they'd be defending themselves, essentially out of the battle unless specifically attacked by the other army. It shouldn't be possible for colonists to completely avoid battle altogether though... If someone attacks a planet and targets the colonists, they'd kill a bunch whether the colonists liked it or not.

So we need a means of desiding how many of them Fight and how many Cower. What better means of desiding this then the Loyalty %'s being discussed by Geoff in the "Natives" Thread.

Perhaps this should be how many colonists you can order to counterattack the invaders. As above, if attacked, it doesn't matter how loyal they are... they'd fight for their life if being gunned down. Disloyal doesn't (necessarily) mean pacifist, but it would mean they wouldn't risk their lives if not forced into doing so.

Perhaps a goal of attacking a planet could be to preferentially kill colonists who you haven't been able to persuade with propeganda. This would increase the ratio of those that support you to those that don't... maybe... it might also make them hate you for attacking violently... Maybe cultural factors influence the reaction.

Additionally, you could perhaps coordinate an invasion with the local resistance who are loyal to you, so that when you attacked, you'd get a large colonist rebel army rising up to fight with you.

More additionally, if some of a planet's colonists were provoked to rebellion without direct ground forces support from another empire, a player vs. rebels AI battle would ensue. The rebel colonists would attempt to take control of the government. How exactly this would work I'm not sure...

Maybe really unhappy and disloyal population (or enemy espionage) can generate "rebel marines" who can take over the government of a planet just like invading marines from another empire. (causing the planet to have a violent revolution and seceed from your empire.)

As long as you had more marines on the planet than the rebels, they wouldn't be able to take over. Or even if you didn't have marines, they'd need more rebel marines than the standard ratio of marines for defending population to take over the government (say 1:500 marines to population).

You could also force a confrontation with the rebels before they actually attack, to "put down the rebels". This would likely make the long-term situation worse though, as violent rebellion quashing tends to make popuations even more unhappy / disloyal than they were before.

how about making "Colonists" a unique thing differnt from both "Soldiars" (high combat power/no productivity) and "Workers/Citizens" (low combat power/high productivity). Colonists would be Medium in Both areas ...

I'm pretty sure having different classes of population for production calculations would be too close to some of the reasons Aq gave for why it was decided to only have one player race / planet. If there's a difference between regular population and colonists for production, it would have to be yes/no, not "medium" or degrees of productivity.

A small % of your population is naturaly "Born" as Colonists and are willing to undergo the dangers of interstellar travel to strange new worlds.

With more expansionist races having more born... and government / specials etc. influencing the number?

I'm see-sawing on the idea of having a separate class of population / ground troop called colonists... It doesn't seem compellingly beneficial enough to be obviously worthwhile...

If they are separate, imo colonists should be built like any other ground troop, requiring time and production / money. The cost and time would depend on loyalty, race, government, happiness, current planet population, etc.

It might be simpler to just have a cost to load regular population into transports, depending on the same stuff as above. This could be subject to a per turn limit as well...

[Daveybaby]

I think maybe the willingness of colonists to fight could be something which is related to racial characteristics/psychological makeup.

e.g.
'warrior race' always spoiling for a fight - in fact, they tend to get involved even if you dont want them to
'hive race' basically will do what theyre told - if you want a suicidal charge against armour just to create a diversion, then they wont even bat an eyelid (assuming they have eyelids, natch).
'average race' a proportion of the race would be willing to fight, but not all - the exact proportion willing to get stuck in might depend on many factors, e.g. how much your race likes/dislikes the enemy.
'pacifist race' : civilians will rarely if ever agree to fight, unless its a case of fight or die. Conceivably some races might actually choose to lay down and die rather than be aggressive.

Of course these characteristics might have other (positive and negative) effects outside of ground combat. e.g. warrior races might become VERY troublesome if their unrest level increases.

Governmental policies might also have an impact, e.g. indoctrination/brainwashing/propaganda, plus the degree of military training given to civilians (e.g. conscription, territorials etc).

[Geoff the Medio]

Conceivably some races might actually choose to lay down and die rather than be aggressive.

Or be mentally or physically incapable of fighting, at least without specialized equipment (tanks, spaceships etc.)