Monday, September 14, 2009

The Rules of War

The Rules of War

Warfare Mechanics Inspired by Sun Tzu

Written by Jarvis Mishler

When 600 soldiers attack 1000 farmers, most rpgs break down. These rules handle large battles quickly, with just enough flavor and drama to maximize the fun, while the PCs get a chance to influence the battle around them!


Give the larger army 10 tokens. Divide the number of troops in the army by 10 to determine the worth of each token. Give the smaller force a proportionate number of tokens (round up). This represents quantity alone, quality is factored in next. Size, for both armies, may be doubled, tripled, etc. for more ‘dramatic’ battles.

Example: if 1000 farmers have 10 tokens, then 600 soldiers have 6.


There are six fundamental factors to determining the outcome of a battle. Superiority in all six of these factors all but guarantees victory. Therefore, advantage in any factor grants an army 1 Strength. Determine which army possesses the advantage in a coming battle by answering the following questions:

  1. The Way – Which army possesses the highest morale?
  2. Heaven – Which army benefits most from the weather, time of day, etc?
  3. Earth – Which army gains more advantage from the terrain?
  4. Leadership – Which of the two generals is the better leader?
  5. Discipline – Which army is more skilled, trained, and supported?
  6. Steel – Which army uses the best weapons and technology?

No significant edge, grants no bonus for that category. Clear advantage grants 1 Strength.

Example: Soldiers have high morale, good leadership, great discipline, and good weapons, giving them 4 Strength. Farmers gain advantage only from their home terrain, leaving them with 1 Strength. The sky, cloudless and clear, grants no advantage and no bonus to either side.


To do battle, each side will implement a simple strategy to apply its Strength most effectively against the enemy’s Size. Each round of battle consists of the following phases:

  1. Strategy – Armies choose how much Strength to apply to defense and how much to offense
  2. Chaos – Armies roll 6 dice and count successes
  3. Strength applied to offense adds automatic successes
  4. Strength applied to defense subtracts successes from the opponent
  5. Reckoning – Each remaining success lowers the opponent’s Size by 1 token

Example: Soldiers apply all their Strength to defense and farmers apply theirs to offense. Both armies roll 6 dice, soldiers roll 2 successes and farmers roll 4. After factoring in Strength, soldiers end with 2 successes and farmers end with 1 (4 rolled, plus 1 automatic, minus 4). Soldiers lose only 1 Size while farmers lose 2. The soldiers’ victory proved costly.

Spotlight Missions

After each round of battle, PCs can volunteer for spotlight missions in an attempt to affect the factors contributing to the opponent’s Strength or their own. Many PCs can volunteer for the same mission, thus fighting together and increasing the chance of success, or separate to take on several missions. Missions can be anything the PCs dream up, scouting, assassination, demolition, etc. It’s up to the GM to determine the difficulty and opposition for each mission, but they are under no obligation to make a tough assassination attempt easier should only a single PC undertake it.

Note: Only PCs not directly contributing to Strength can undertake spotlight missions. A PC acting as the general of his army, thus contributing Strength through Leadership, cannot step down for a secret scouting mission without forfeiting his contribution to Leadership as well.

Missions are resolved using the normal rules for the rpg you’re playing. A spotlight mission can be detailed and drawn out to add drama or shortened and summarized to speed the action. Ultimately, each spotlight mission should produce an opposed die roll to gain, or maintain, the advantage. After the roll, the Strength point for that factor goes to the winner.

Example: Two farmers attempt to break the soldiers’ morale by taking a mission. They decide to defeat a group of 10 soldiers in a spectacularly flamboyant fashion, loudly proclaim themselves to be “Dragon’s Chosen Warriors of His Holy Wrath”, and so fear and uncertainty among the soldiers. Should they succeed in defeating those 10 soldiers, they’ll probably need a bluff roll vs. the soldiers’ will or their general’s leadership as he attempts to rein in his men. Their bluff roll may be easier or harder should they defeat more or less soldiers.

Players should be encouraged to get very creative with ideas for spotlight missions, but GMs should step in with any ideas or alterations of their own. If a PC wizard wants to use a “Heat Metal” spell to melt enemy swords, the GM should help out by declaring the number of swords necessary to make a difference.


An army is defeated when all of its Size tokens are lost. Whether this defeat is due to destruction, rout, or retreat simply depends on the narration up to that point. After the battle, each army attempts to recover its losses by rolling 1 (loser) or 2 (winner) dice for each Size token lost. One Size token is recovered for each success on this roll as warriors are healed, pulled to safety, etc.

Dice Pools

Missions always use the normal rules employed by the rpg you’re playing, but a simple dice pool is used during the ‘chaos’ phase of combat and recovering casualties. If the rpg you’re playing doesn’t already use dice pools and successes, just grab some six-sided dice. Any die that rolls 4+ is considered a success. A high target number (5+) places more value on Strength (automatic successes) where a low target number (3+) introduces more randomness during the battle. These rules were written with a 30% chance of success in mind (8-10 on a D10), but you are encouraged to adjust this as you wish!


  1. My first impressions:

    1) Cool, looks like Reign's company rules but much more streamlined and focused on mass combat.
    2) Aw, no interesting decisions.*
    3) Aw, no Lanchester's Law.**
    4) Nice recovery rules!

    What about one extra rule/mission... surprise. Usually both armies choose attack/defense levels simultaneously (and usually it will be obvious which to choose :)). If one side has significantly greater scouting/recon/scrying/etc then they may assign Strength after seeing their enemy's Strength assignment (and maybe die roll?). PCs can go on a mission to gain/nullify this advantage.

    *...since all the bonuses are fungible (+2 Strength is just as good no matter where it comes from). This has the benefit of letting the players choose from a wider range of missions without taking penalties in the battle for suboptimal mission choice and the detriment of giving the players essentially only 1 meta-level decision: whether they can get a +2 Strength for switching from -1 to +1 in a category or whether they have to stick with a +1. And usually it will be quite obvious how much Strength to put in attack and defense.

    **For games with mass aimed range weapons (not volleys of unaimed arrows) it'd be nice to have the square law apply rather than linear but I guess we can forgoe it in favor of simplicity. Anyone who cares can mod it anyway. :D

  2. Who is it that must answer those six questions above? I bet there may be some conflicting answers when two players are personally invested in the outcome of the battle. I do really dig that you alternate between large-scale rolls and small-scale missions that augment those rolls. Very cool.

  3. Guy, thanks for all the great comments. Scouting/recon/scrying etc are all simply factored in to the advantage for Leadership. The more up to date your information, the better your tactical decision making. Lancaster's Law says more guns = more casualties. That sounds a lot like +1 Strength (Steel) for me. If it needs to equal +2 Strength in your game, go for it!

    As far as choosing which Missions to undertake, surprises can be thrown in all over the place. Say the PCs opt to assassinate the general and thereby gain advantage for Leadership. Well, what if that general is a righteous prince and the 'chosen one' of his people. You've not only called their Leadership into question (time to roll), but you've inadvertently raised the enemy's morale cause now they fight for honor!

    Daniel, the six questions are just answered by the people gathered at the table. There's no need to argue that your berserkers are better than his spearmen. If both armies have an advantage, neither army does. "Significant edge" or "clear advantage" are the only ways to gain that Strength bonus.

  4. Sounds good! Checkin' the math with some back-of-the-envelope...

    Right now each side inflicts baseline ~1.8 casualties per round, so equal forces will wipe each other out (the most common outcome). With a single +1, you can inflict ~1.8 casualties to their ~0.8 per round, so your force and another 2.25x its size will wipe each other out. With +2, your force and another 5.4x its size will wipe each other out. And +3 lets you and 20x you wipe each other out. Since the system only handles 10x, each +1 is nearly equivalent to doubling the size of your force.

    How does this change if successes are 70%? Then you've got ~4.2 casualties per round. A +1 is 1.3x, a +2 is 1.9x, a +3 is 3.3x, and a +4 is 7.8x. So a little bit of Strength helps a bit, but once you've got a lot it's by far what matters again.

    Nothing looks crazy weird to me on paper. I'd make a swing of 2 Strength (your enemy had +1, now you do, and no other bonuses changed) very hard for the PCs to accomplish.

    Also note that in almost all circumstances you'll want to put a superior Strength into defense and an inferior Strength into attack. Not sure whether that's good or not. Hm, I guess except if you're the PCs' side, in which case you can defend until the PCs swing the battle in your favor. Then you'll keep defending. Okay... when would the PCs want (mathematically, not fictionally) to attack rather than defend?

    Let's try the most extreme case. The PCs have raised an army of peasants to overthrow the knightly lords. The peasants have morale and the knights have everything else. Say the knights don't have metagame knowledge that PCs are friggin' awesome. Then they "should" put +5 defense and the peasants +1 attack. But in fact the PCs are awesome and know it. If the peasants know that (say) the knights will be losing about 1 Strength per round, can they do better by defending the first few rounds? Round 1 they lose 1% to win immediately and save 1 token. That seems great. Once the knights are down to 4 Strength the peasants by defending lose like 6% to win immediately and save 1 token, which is still quite nice. Once the knights are down to 3 Strength the peasants by defending lose 18% to win immediately and save 1 token... still worth it. Looks like the peasants should attack only once the knights are down to about 2 Strength. And if the peasants aren't quite as numerous, starting the knights at 2-3 tokens, it's much worse to attack - they should just defend until the PCs do their thing.

    It may be nice to slightly incentivize the first point of attack (e.g. if you have *any* nonzero Strength in attack you also roll an extra die).

    Also if there's more like a 70% success rate then it's not worth defending until the PCs swing the battle when you've got inferior Strength.

  5. Wow. That's a lot of numbers. :)

    A truly larger and powerful army (+6 Strength) could easily choose to pour it all into offense, thus eradicating a smaller army utterly with only minor casualties.

    Also, 6 dice on 50% odds will roll an average of 3 successes. Therefore an army with 6 Strength need only dedicate 3 to defense (negating the opponent's average roll) and leaving the other 3 for an average attack of 6 successes. Possibly destroying the smaller army in a single round again, while taking no casualties at all!

    Keep in mind that the strategy of applying Strength exists out of game only. In game tactics and strategy are factored into advantageous Leadership. Some armies (berserkers, zombies, vikings, orcs, etc) will probably never fight defensively, while other armies (legionnaires, spartans, etc) will.

    There are a great many rulers that care only about winning the battle, not about the casualties.

  6. (I was using 30% for those numbers unless otherwise specified)

    If extra rounds carry fictional consequences (time passing is by far the most obvious) then perhaps putting the Strength into attack is a fine decision, but otherwise definitely not. An army with 6 Strength can guarantee taking no casualties by dedicating 6 to defense, so why would the players of that army gamble? Only if fewer rounds is better or for some reason the players *want* to take casualties. So put a note: when applying this mass combat template, make it be the case that fewer rounds is significantly better unless you want the players of the side with the larger Strength bonus to put all their Strength in defense no matter what. It's not just about minimizing casualties - in most cases putting a superior Strength on defense makes you more likely to win the battle, straight up.

    That's the reason Feint exists in Burning * Duel of Wits. If it or an equivalent didn't, a side with significantly more dice would have huge incentive to just Rebuttal every time.


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