Rules for the Sengoku Jidai

The Sengoku Jidai, or the Japanese Age of Warring States, has long captured my attention and interest. The turbulent history and larger than life figures have offered prime material for any number of games, books, films, series, and more and I’ve always had an interest in the exceptionalism of Japanese history, how it rocked between long periods of insularity only to go through short bursts of seismic change. The Sengoku Jidai is one of these periods.

Brief History

Map showing some of the major clans of the era.

It is typically reckoned to have lasted around 150 years, from 1467 to 1615, and completely changed the socio-political makeup of Japan. It began with the Ōnin War, a civil war between two mighty clans under the Ashikaga Shogunate, but then spread to become a series of near constant civil war between rival clans across Japan. Powerful ancient families would fade into history and arrogant upstarts would rise to prominence only, in many cases, to fall. Famous clans like the Oda, Tokugawa, Uesugi, Takeda, Hojo, Shimazu, Date and Mori would stamp their legacy into Japan’s history as they fought for control of the provinces and country.

While Japan claims an Imperial family stretching back to the dawn of time, by this period the power of the Emperor had been reduced to that of figurehead and governance lay in the hands of the Shogun, the overall military commander of the Empire. Over the centuries, the Ashikaga clan holding this position had weakened and power became increasingly concentrated amongst the vassal clans in the provinces outside the Imperial capital of Kyoto. These clans formed a complex hierarchy or vassalage and alliance that constantly shifted throughout the period as small clans broke free of their overlords and went on to become mighty in their own right, while once powerful clans fractured to internal and external enemies.

The period ends with the Unification of Japan under the Three Unifiers: the ruthless general Oda Nobunaga who learned how to leverage European style firearms to dominate the battlefield; his successor, Toyotomi Hideyoshi, a mere peasant who rose to prominence through his craftiness and prowess on those battlefields; and finally the great politician and general Tokugawa Ieyasu, who was patient, careful, bided his time until the moment was right then struck fiercely and went on to establish the Tokugawa Shogunate, which would close off and rule over Japan until the late 19th Century.

Tokugawa Ieyasu as Shogun

Warfare in the period was also quite distinct from that found in most other historical periods and regions. Most armies were based around clan structures, and it wasn’t really until the end of the period that particular warlords, or Daimyo as they were known, were powerful enough to break up subject clan troops into larger weapon specific sub divisions. Most armies consisted of a series of mini armies, known as Sonae, each controlled by a Daimyo and consisting of a mix of different troop types. Each Daimyo would bring along their subject clans as well, so an army may consist of the top level Daimyo and the Sonae they controlled directly, then under them there could be a number of senior retainer Daimyo with their Sonae and then junior retainer Daimyo under them with their Sonae and so on. A typical Sonae would be from 300-800 men, though some powerful Daimyo could field ones upwards of 1500 men strong, or even multiple ones. As the period progressed it became more common to split off smaller units to provide specific tactical roles, for instance concentrating firepower, but in many cases battles would consist of conflicts between a series of mini armies on the field.

This was further exacerbated by the terrain of Japan, which tends towards a lot of mountains, forests and rice paddies, none of which are ideal for line up and fight battles. This meant tactical manoeuvring and flexible mixed arms units made a lot more sense than the dense pike and shot formations you’d see in the likes of Europe at the time. Battles could scale from small clan conflicts all the way up to massive battles between vast alliances of clans.

A folding panel showing the Battle of Sekigahara. Note how spread out the battle is over the hilly ground compared to how European battlefield paintings at the time appeared, with their dense formations and more gentle ground.

There’s a superb blog that goes into a lot of details on the structure of these here, but essentially I’ve been giving a lot of thought on how this would be best represented within a set of wargame rules over the past year or two.

Rule Systems

Most rules, especially those for ancient and medieval periods, assume each unit will generally have just one or two weapon types.  Those of Pike and Shot period tend to be quite specific to the European style of warfare, which doesn’t translate so well. There are some 19th Century rules that abstract mixed arms units out, but those tend to focus on the grand sweep of huge battles, which doesn’t quite fit the character of the age. I would be tempted to attempt some of the very largest battles in the period, such as Sekigahara, using this style of rules, where each unit is actually an entire division of clans, making the smallest unit a Te or division. Something like the 19th Century focused rules Bloody Big Battles could work quite well here, as would allow you to represent the different division sizes for different clan powers and there are enough modifiers to indicate tactical efficiency and concentration of firepower, with a few tweaks to the rules to handle the reduced ranges and technology available.

Guns became more prominent later in the period, often proving decisive in battle, especially on the defensive

For small scale games, many ancient and medieval rulesets will generally work well, such as To The Strongest and Hail Caesar. Within the Sonae there is an organisation of sub units based on their arms, known as Kumi, that equate pretty well to a unit of pike or spearmen, a unit of bowmen and/or gunners, some heavy infantry samurai or cavalry, etc. So for fighting battles where it is maybe a small clan vs clan battle of a few Sonae against Sonae this could translate pretty well. They did tend to fight in fairly loose order given the terrain and small numbers within the units, but that can generally be sorted out with most rule sets, which don’t concern themselves too much with specific numbers in units. There are a couple of period specific rulesets that cover this style or warfare too, Killer Katanas II and Peter Pig’s Battles in the Age of War come to mind, though I don’t yet own either.

One of the key aspects of the fighting is the use of complex formations, in which small Kumi of ranged or melee units, usually peasant troops known as Ashigaru (or “light feet”) led by a samurai, would spread out across the front and flanks probing the enemy for weaknesses. At some point there would likely be a charge of the spear troops who would fight until one side revealed a weakness and the elite samurai who would have been supporting the fighting can charge in and attempt to break the enemy. Again for a small game this works fine with many existing rule sets. You could also go smaller again down to skirmish level gaming with individual samurai and retinues, something I may consider in future as I own a Test of Honour starter set, though the rules never really inspired me to paint any of them up.

The difficulty comes from the mid size games. This is where you want the smallest unit to be a Sonae, i.e. each unit is a mixed arms mini-army of different strengths and sizes. This means it needs to be able to handle everything from a detachment of gunners up to a huge Sonae for a powerful Daimyo, without being cumbersome. The way I visualise this is each side will typically have an Army General, the most senior Daimyo, who commands the overall army, which comprises of a number of Commanders, that is the retainer Daimyo under them. Each of those Commanders is in charge of a Te, which itself is comprised of a number of Sonae, each representing the clan army (or detachment) of a more junior Daimyo.

A typical army of around 12 units may consist of the Army General’s Te, including the General themselves with their bodyguard, their own personal Sonae (usually a large size one) then a couple of smaller Sonae/detachments, then two Commanders with their own Te, each comprising the Commanders own Sonae (into which they are integrated) and 3 other Sonae/detachments representing junior clans and detachments. This can easily be scaled up and down to handle different sizes of conflict. Given the shifting natures of allegiance and betrayal, it also adds some nice potential for scenarios, or even multiple players with uncertain loyalties.

This is very appealing for smaller scale figure gaming as it allows for some very interesting basing opportunities. I’m a big fan of this blog, which discusses similar considerations and has some superb 6mm bases on show. At this point I have no figures for the time period, wanting to settle on some rules before jumping in. I’ll likely pick up some 3mm figures that can be done up reasonably generically, then use 6mm or 10mm for when I settle on what clans I’d like to work on and what scales of game I want to represent.

There are some key elements needed for a game of this type. Historical flavour being a big one, as well as the ability to try out historical tactics and the unusual formations that (allegedly) appeared on the battlefields. It should be able to handle mixed arms units in a way that is interesting and characterful. Leaders should be important. Feudal armies were intrinsically tied to their hierarchies and leaders, so they should have a strong presence on the field, while still keeping within the realms of historical possibilities. I did consider some form of duelling/challenge mechanic, but that is more something that would happen at the level of the individual combatants, not the grand tactical level of the commanders, despite what some romantic histories would have you believe!

Armies often fought in complex formations with multiple layers of attack and defence.

I’ve not come across any rules that really achieve that for me, though I may try and get my hands on BAW and KK2 at some point to see how they fare. There are some board games, Tenkatoitsu for instance, that do apparently model this somewhat and a few people have been looking at adapting this to miniature wargaming, but I’ve always had an interest in writing my own rules and this seems as good a possibility as any, so I’ve been pushing around ideas over the past while on what this sort of game would look like.

This is interesting for me as it’s making me really analyse what I do and don’t like in wargame rules to find a system that will really work for me. One thing I find I don’t overly like is extensive wound tracking. I dislike having to push a lot of dice and counters around with units when moving them, as dice are easily knocked over or mistaken for rolled dice, and when you can have more than 6 wounds you end up with multiple dice, or polyhedral dice even more prone to being knocked over.

One or two status markers is generally okay, especially if thy can be modelled to fit with the unit on the table. TtS! does this well, where most units typically only have 2 or 3 hits total, meaning you’re usually only needing to track a small number of wound tokens. I’ve taken to making one or two wound tokens with most units I make for this purpose.

I like the idea of unit status rather than strict wounds. Most modern systems are more concerned with the overall morale of a unit than specific strength reduction through damage and this is a system I favour, so my plan would be for units to have particular statuses rather than a certain number of hits.

As far as period combat goes, looking at ranged combat in the early period it was rarely decisive. Given the relatively short ranges of bows and early guns along with the looser formations of troops, ranged combat was generally not the deciding factor in battle until much later in the period where concentrated gunfire was used to devastating effect. Bows and guns were generally mixed together in varying proportions, so any ranged combat rules need to reflect the proportion of guns and bows more than differentiating the specific weapon types. Even when guns became much more prolific, they were still of primary use in defence, while offensive actions tended to favour melee. After the period, during the Invasion of Korea, the Korean and Chinese troops were more afraid of the Japanese steel than they were of the gunners who while numerous, were not considered particularly good.

As such, I want melee to be pretty decisive. Accounts seem to indicate that most melee that isn’t resolved in the initial clash can go back and forth along the line of combat until one side creates a significant breakthrough and has an opportunity to destroy the enemy. This is something I want to represent in the rules, with the standard melee phase representing the fighting between the Ashigaru spearmen, then a shock phase when one side comes out on top representing the elite samurai exploiting an advantage.

Given the nature of the clan relations, I also want something a bit more characterful with the command and control system to represent different general personalities, and to give players meaningful decisions about what to do with their generals. Typically the General would sit somewhere with a good view of the battle field surrounded by a mako screen and their bodyguards, but would also mount up with those bodyguards and charge into action when needed. I have plans to treat the general differently depending on which of these states they’re in.

The core of what make any game fun and playable is the mechanics. This is probably the key area to settle on first since the flavour tends to flow around the mechanics. There are two main parts to this, the actual means of controlling units and how they fight, them the means to hire those fights are resolved with some level of randomness. I’ll begin with the latter here.

There are, to my mind, several potential systems. One is a modified d6 system. This means for resolving pretty much any action you roll a six sided die and on a certain value it is a success. My vision for this was that the “standard” success was on a 4+ and various modifiers would move that up and down. I played a couple of test games (with pencil and paper anyway) using a system based on this and found it to be unsatisfactory. I spent a lot of time doing mental maths and mostly forgetting modifiers, so there was less of an instant “yes, it hit!” and more of a “oh I think it hit, add this, take away this, and yes…no…yes yes it hit. okay moving on…”, which doesn’t have the same impact. I also found I didn’t enjoy the act of throwing one dice over and over again.

The outcome of one of my test games. At the bottom the attacking force ground down the defender, assaulting the general’s HQ, but a relief force managed to break through the delaying force of the enemy at the top and in a daring dash, catch the exposed enemy general in the flank and drive him from the field.

I had always been somewhat put off the “bucket o’ dice” idea of gaming having seen some of the crazy numbers of dice that can be involved, but I’m actually finding that a moderate amount of dice throwing is okay, up to about the limit you can hold in one hand. There’s something much more satisfying about throwing a handful of dice than just one. My current thinking is that the mechanics consist of rolling 4 d6 as standard, then adding or removing dice (down to a minimum of 1 d6) based on situational modifiers, with success being on a 6 appearing. I don’t want to have too many of these as I want to keep things simple, but certainly things like terrain, actions and morale will play into it.

I quite like the idea of opposed rolls, where both players involved partake in the action. My current thinking is that for a shooting or melee action both sides roll their required dice and count the number of successes, then various outcomes can depend on that. E.g. in a melee if both miss then both sides pull back, if both hit the same amount, they remain locked in combat and if one sides scores more hits than the other, then things can get pretty nasty for the losing side. I’m using my trusty pencil and paper to play out some games with these mechanics to see how they fit with satisfaction, and to ensure they stay more in the cup ‘o dice than the bucket ‘o dice territory, though resolving multi unit combats is the biggest risk of buckets.

Another test game. The attacker moved in from the north west to assault the defender across a stream. The relief force attempted to join the defender but was pinned down while the attacker moved to the stream, but a fearsome defence repelled the attack and the relief force engaged with the main enemy army in a dramatic multi unit fight that broke the attackers main division. In a fit of frustration the attacking general charged the relief force commander in an attempt to drive him from the fight, but was cut down dead.

Another possibility is creating some form of Combat Results Table, where you throw, say, two dice, add them together, then compare that against a table with modifiers. I’ve seen a few quite scary examples of this, going multiple layers deep, but some systems, such as BBB, do it quite well and it’s easy to follow on a QRS. This is a potential option, but I’d quite like a system that has the immediate feedback of knowing that an action is a success without having to constantly refer to tables. I may explore the CRT in future, but for now my experiments lie more with hit dice.

I generally want to avoid “unusual” dice. That is to say d8, d10, d12, d20, etc. I have no massive objection to using them myself, but I feel they can be a barrier to entry for some people and I find tend to work better for a modified single dice system, or one with lots of complex variables. A possible exception to this is the d10, which Simon Miller very cleverly got around in To The Strongest and For King and Parliament by using a familiar deck of cards to simulate similar results. I may come round to such systems if the number of dice start getting out of control, but for now I plan to stick to standard d6.

In the next post I’ll cover some more of my ideas around the mechanics of taking actions within the game as well as a bit of a battle report of a larger pencil and paper sample game.


  • The Sengoku Jidai was a period of bloody civil war in feudal Japan.
  • The terrain and complex clan hierarchy meant armies were more retinues of retinues than strictly organised armies.
  • Each unit in the army may be a mini army unto itself with mixed arms.
  • Most rulesets deal with the actions of small armies and their constituent parts rather than these mixed units.
  • I’m having a go at developing my own rules to cover this.
  • Having toyed with a few types of resolution mechanics I’ve had some success with a dice system somewhere between a single modified dice and a large bucket of dice.
  • Next time a little more on the action mechanics for movement, combat, etc, and a battle report.

Thanks for reading,


2 thoughts on “Rules for the Sengoku Jidai

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