Sunday, November 6, 2016

Multifront Battles in GURPS Mass Combat

My experience in running games is that if you have some kind of battle mini-game in which multiple people are on the same side but only one player gets to make significant choices, then the players who don't get to make choices are going to find it very boring. The example that sticks in my mind is a Star Wars game I ran when multiple PCs jumped into a single large starfighter: one PC was the pilot, and got to maneuver the ship and fire weapons, and other PCs were secondary gunners, the damage control engineer, and the the guy who ran the shields. The pilot had a reasonably degree of fun maneuvering the ship, dodging enemy fire, and shooting enemy fighters. The secondary gunner had some fun shooting enemy fighters. The engineer and the shield operator, even though they nominally had decisions to make and got to roll the dice every turn, became bored very quickly.

I bring this up because I'm thinking about running a GURPS game about Mass Combat. In GURPS Mass Combat, there's normally one commander who decides the strategy and rolls the dice, and any other PCs can choose the amount of risk they want to take for significant action that might affect the battle but otherwise aren't making big decisions. My expectation is that for the players who are interested in Mass Combat at all, that the only fun position will be the commander and choosing risk and attempting significant actions will be at best a sad consolation prize. The way to keep everyone interested is to split a single battle with a single commander on each size into multiple fronts, one per PC commander. That way, everyone gets to make important decisions.

Mass Combat has some rules for running three-sided battles and subordinate commands (Mass Combat p40-41). Ironically, they advise merging multiple allied sides into a single unified command, so I'm going to disregard that advice and come up with my own house rules.
It's the historical solution, really.

Multifront Commands

These rules apply when multiple PC commanders are attached to the same force that is campaigning as one unit. These rules obviously don't apply if the PCs are each commander a force that is campaigning separately, as obviously those forces are going to encounter different enemy forces at different times with different reconnaissance contests.

A force with multiple PC commanders has to have a single overall commander and intelligence chief during reconnaissance operations. It only splits into multiple fronts when the battle is joined. After that, each front is a separate battle for purposes of calculating troop strength and class superiority, defense bonuses, positional bonuses, casualties, and the like.

Dividing Forces at the Start

Before the first round of combat, the PCs need to split their forces into individual fronts and assign a commander PC to each front. They can do this however they want: equal split of all forces, assign one player all the cavalry and split the rest, give one player all the units of the same race in a multi-racial force, whatever. The only restrictions are that each PC needs to have enough units to be interesting: preferably at least 10 units. Players need to work out the details among themselves, with the overall commander having final say aside from a GM veto in the unlikely event that people are being jerks.

The GM also needs to divide the enemy force as he sees fit, based on the personality of the overall enemy commander. One enemy commander can be assigned to multiple fronts, or subordinate commanders can be created and assigned, as appropriate. In general, each front should have a proportional share of the total enemy force relative to the share of the PCs' forces in the front, but the GM can make decisions as he sees fit: he can assign all the Marine troops to the river crossing in one front and all the cavalry to another front, if that's an appropriate decision for the NPC commander.

The side that lost the reconnaissance contest divides their troops first, and the side that won responds to that division based on the initial intelligence for the battle type (Mass Combat 30). In the case of a tie, the players split their forces first but can reassign entire fronts after the GM has split his forces.

Fighting the Battles

Each front is its own separate battle, and the decisions in one front have no effect in another front. It's possible for a PC commander to win an overwhelming victory and wrack up +8 in PB on one front while an allied commander is slowly losing ground in another front.

One exception to this rule is the length of the battle round, which is determined by the total size of the smaller force involved, not the smallest force in any given front. So if the smaller force is 1500 elements, then each battle round is 2 hours, even if the smallest force in a front is only 5 elements.

Transferring Troops and Collapsed Fronts

After any round of battle, troops can be transferred between fronts freely. Troops get the PB of the front they move into and calculate casualties as the worse of the front they left and the front they're moving into. Calculate TS and class superiority normally based on the new troops in the front.

A front is collapsed if it has taken 100% casualties, or has won or tied after choosing the Fighting Retreat strategy, or has completed a Full Retreat strategy. An enemy with a collapsed front MUST reinforce with fresh troops, since there's still a PC that needs to fight. The reinforcing troops calculate casualties and PB normally, to a maximum of -50% casualties for the reinforcements and +5 PB for the other side. A PC with a collapsed front can either get reinforcements, using the above rules, or sit out the rest of the battle in which case any enemy troops in his former front can be moved to other fronts. This doesn't apply if all fronts on a side are in collapse at the end of the same round: the battle is over and the pursuit can possibly begin.

Note that it is legitimate to have multiple fronts Retreat while one front remains fighting a rear guard action to hold up pursuit. This is generally pretty rough on the troops fighting the rear guard.


Any commander on any front may start a Parley, but the Parley only occurs if all commanders on all fronts agree to it. If a Parley attempt fails, only the commander who started the Parley takes the penalized Defense strategy, not all commanders on his side.


In a multifront siege, some fronts may be involved in Deliberate Attacks against Deliberate Defenses (called "siegework") while other fronts may choose different strategies (called "activity"). Split each siegework battle round into 6 segmented battle rounds during which activity can take place. Only roll for the siegework battle strategies at the end of the 6 segmented rounds, and only if the forces involved in the front performed siegework for at least 4 of the 6 segments. If a front did activity for three or more segments, treat any segments that were intended to be siegework as though the attacker had chosen the Attack strategy and the defender the Defense strategy and resolve them all at once after the six battle round.

Example: Rachel, Derick, and Will are PC commanders besieging the Ebon Citadel. Rachel and her opponent choose Deliberate Attack and Deliberate Defense, each, for all 6 segments. Derick starts by performing an Indirect Attack into his opponent's Deliberate Defense on the first segment, then tries a Deliberate Attack against his opponent's Mobile Defense on the second segment, and then both switch to Deliberate Attacks and Defenses for the last four segments. Will chooses Deliberate Attack for all six segments, and his opponents chooses Deliberate Defense for the first three segments, but then chooses to Raid for the last three segments. Derick's Indirect Attack versus a Deliberate Defense is resolved immediately, followed by his Deliberate Attack versus his opponent's Mobile Defense, followed by a single Deliberate Attack versus a Deliberate Defense at the same time that Rachel's Deliberate Attack versus a Deliberate Defense is resolved. Will separately resolves three Attacks against three Defenses and then three Deliberate Attacks against three Raids because his troops were not able to spend enough time making Deliberate Attacks.


  1. Great stuff, Mark.

    I'm following this "mass combat campaign" idea with interest - I've always wanted to run, or play in, something like that, but I've never been convinced that GURPS Mass Combat is up to the job as written, since it (understandably) focuses on getting the battle over with, so as to get back to focusing on small-group interactions as usual. What one really wants are full-on tactical wargame rules, which also has interesting map-based options at the strategic level, combined (of course!) with a full kingdom-wide resource management system.... But then, obviously, we're talking about a whole 'nother game.

    Stepping down from those lofty heights, these rules for playing multiple front battles seem like a great thing.

    One question I have (which may be a silly one - I'm not really terribly fluent with GURPS Mass Combat). I notice that these rules allow you to redistribute your entire array of forces freely at the end of each round of battle. This might be ok, but it might also stretch credulity, if every unit can just head over to the opposite end of the battlefront every few hours, and then head back to the opposite side of the battle at will a few hours later....

    I wonder if it would be more fun to limit the ability to redeploy in some way, thereby adding both flavor and tactical depth as you make difficult decisions.

    Two options:
    1) What about saying that only units held in reserve can be used as reinforcements? That has a certain amount of realism to it. It would also create dramatic tension (When do we commit our reserves? On which front? Knowing that once they're committed, they're committed...) Different PCs (or NPCs)could also have a different amount of say over where and when the reserves are used, thus generating more opportunity for dramatic social conflict ("But Sir! The left flank is crumbling! We must send in the reserves!" "But my beloved wife is fighting on the right flank, and I will never betray her... Send the reserves to the right!")

    2) Alternatively (or in combination with the "reserves" idea), you could say that at the end of the round, troops can only be moved to an *adjacent* front. That would make the overall structure of the battle matter, and create opportunities for tactical decisions to be made about where to place units so as best to allow them to reinforce one another if needed. It would also stop units rushing all over the place, willy-nilly, while still allowing a lot of flexibility. If you *really* wanted to go to town, maybe very mobile units like cavalry, flying troops, etc, can be redeployed wherever you want, but ordinary foot troops can only be redeployed to an adjacent front.

    Jut a few thoughts. Possibly irrelevant - as I say, I don't know the GURPS Mass Combat system very well, having read it but not used it in play.

  2. No offense, but while you might want full tactical rules and a full kingdom-wide resource management system, that's not at all what I want. What you want sounds like the Crusader Kings video game. I don't play that game for a reason.

    Forces can move between fronts freely. That's not 100% realistic, but it's not something I expect to change. The main limiting factor is casualties - If you move a force from Front A, where there are 0% casualties, to Front B, where there are 25% casualties, and then back to Front A, then Front A now has 25% casualties - and in Mass Combat, each 5% casualties is a -1 to the Battle Strategy roll. People are only going to rearrange their forces when they have to, I expect.

    My real concern with moving troops is twofold: make sure that the players running PC commanders always have troops to command while a battle is going on (because that's part of the social contract for running a Mass Battles game) and minimizing busywork. I don't want to get into a situation where Fronts B and C get wiped out and although Kevin's troops are doing fine in Front A, he can't reinforce Front C because it's "realistically too far away" and now Eric has to sit out a round of combat. So troops have to move freely between fronts. Similarly, I don't want to get into a situation where Kevin moves his infantry to Front B so that Front B's infantry can move to Front C, and then everyone has to recalculate their troop totals and whatnot. Front A's infantry can be moved directly to Front C, and then there's only two recalculations.

    Anyway, thanks for the feedback. There's still an open slot in my group's roster if you're interested in playing an online game.

  3. Hi Mark,

    It's now nearly a month later, and I just realized that I never thanked you for this rich and interesting response. I take your points about troop movements between fronts - especially the importance of avoiding the "A moves to B so B can move to C, so everybody has to recalculate everything" situation. I hadn't thought of that; it would certainly be a pain in play, just as you say.

    Just to aooid miscommunication, I should perhaps clarify that I wasn't really entirely serious about needing a full GURPS system that would cover everything from the kingdom level on down - rather, I was having a bit of a laugh at the absurdity of my own rapidly expanding desires. I see Mass Combat and think: "Yeeeessss! More! Bigger! More! Mwahahahaha!!!!"

    In any case, I'm very much looking forward to your next updates about your upcoming mass-combat-based campaign. Is that the campaign you're referring to when you say "there's still an open slot in my group's roster"? Or do you mean Nu World? In any case, I appreciate the invite. I must admit that, generally speaking, I'm not really one for playing tabletop online - though this mass combat campaign sounds fascinating enough to make it very tempting.

    1. Sorry for a late reply to a late reply.

      We've just finished Nu World and are gearing up for New Dawn (campaign wiki here: The offer to play is still open.

      I get the point about wanting to do more and bigger stuff with Mass Combat. Still, I'm sticking with doing the least I can to have a solid campaign based around Mass Combat. In gaming, I rarely find myself thinking "I underprepared in scope, we could have done so much more" but often find myself thinking "there was a lot of stuff I prepared that never went anywhere." I'm not even sure if a Mass Combat focused game is going to be enjoyable at all. Going crazy with kingdom management feels unwise until I know the Mass Combat works well and is fun.


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