Rules for the Sengoku Jidai: Core Mechanics

In my last post I gave a bit of background for my thinking on how a Sonae based Sengoku Jidai ruleset might work and some of my early experiments with it. To recap, the Sengoku Jidai refers to the period of civil war that devastated Japan in and around the 16th century. Armies were generally organised into sub units of mixed arms clans known as Sonae. The terrain of Japan meant warfare tended to favour looser formations and manoeuvre than would typically be seen elsewhere in the world at the time.

For the moment I’ve settled on “hit dice” as my randomisation method, namely rolling 4 dice, adding or removing dice based on situational modifiers, then counting any 6’s as a success. In this post I hope to explore some of the core mechanics I’ve been trying out; command and control, movement, combat and morale.

I am writing these into a more “technical” rules document, but wanted to lay out some of the general concepts here. At the end I will have a brief pencil and paper battle report to show how some of the mechanics play out.

Command and Control

This refers to the means in which the players actually command their armies and give orders to commanders and units. There are essentially three levels of command. The first and lowest level is the individual units, typically a mixed arm Sonae, commanded by a Samurai-daisho (military leader) a minor Daimyo (feudal lord). These commanders are abstracted into the units themselves and assumed to be dealing with the individual allocation of troops within the Sonae.

Multiple Sonae will generally be grouped together into a Te, or division. The most senior, and usually most powerful, Sonae within this division, is known as the Honjin (or headquarters Sonae), usually commanded by a senior Daimyo. This Honjin Sonae is the Commander for the entire Te, and is the one from which actions to the individual units will flow.

An army will generally consist of several of these Te with the leader of the most senior Daimyo’s Te being designated the overall Army General. Unlike the Commanders who are embedded into their Honjin Sonae, the Army General is treated as a stand alone entity based separately to a Sonae, though they will usually have one or more powerful Sonae in their own Te commanded by trusted retainers, usually including a Honjin Sonae with it’s own Commander. Typically there will be one Army General per side, but in large, multiplayer battles, there could potentially be multiple Army Generals, each leading their own set of divisions in coordination with their ally. This can lead to some fun possibilities for betrayal and treachery, as was common in the period.

These Army Generals may be in one of two states. The first is “Encamped” whereby they are based with their Maku screen and retainers, usually in a prominent but well defended position in the battle field. In this state they have powerful defensive modifiers, can send out messengers to their commanders, but cannot move themselves.

The second is “Mobile” whereby they mount up with their personal unit of bodyguard troops, known as the Hatamoto, and become a powerful unit in their own right with rapid movement but no ability to send out messengers to commanders and a greater chance of personal injury.

The fourth Battle of Kawanakajima: Takeda Shingen Vs Uesugi Kenshin - by  Dmitry Filatov. | Takeda shingen, Samurai art, Japanese history
There is a somewhat fanciful story of the great rivals Uesugi Kenshin and Takeda Shingen engaging in a brief duel when Kenshin, mounted with his Hatamoto personal guard burst into the Takeda camp and engaged an unprepared Shingen, who was forced to defend with his steel war fan until his own Hatamo could drive Kenshin off. While it likely never happened, it does provide a good example of the two different ways Generals can operate.

Given the hierarchical clan status of the armies, the loss of a Commander will generally mean the loss of an entire division, and the loss of the Army General will usually spell the loss of the entire battle. So there is a fine balance between using these as powerful offensive units, while keeping them safe from harm at risk of collapsing the army. There is some potential around loyalty and successor mechanics that may mitigate this collapse somewhat, likely a series of Morale tests for the units and a test or special trait that allows a Commander or General to have a worthy successor to take the reigns of battle, but I’ve still to shake out the details on them.

Each commander (including the general) will have an Authority value representing their right to rule and the respect they hold from their retainers. This can be a positive or negative value, depending how powerful or weak they are. This value will be used to modify the number of orders that they can give. The commanders will also have a Command Radius that extends out from their unit, with Authority increasing or decreasing the range. Any units outside this Command Radius may only be given one order per activation. Any units within the General’s Command Radius will gain a bonus to their Morale tests.

At the beginning of each turn the player will decide if their Army General is Encamped or Mobile. If Encamped then they may designate a Commander to send a messenger to. If both the General and Commander are out of range of any enemy units then this is decided with a simple 4 + Authority d6 check (success on at least one 6). If either is within range of the enemy, the check is opposed and must score more successes than the enemy to succeed. If successful, then that commander can add the general’s Authority along with their own to their next activation. I did briefly toy with having messengers as their own units that travelled across the battlefield, but it became somewhat messy and required remembering which messenger had been directed at which commander. I suspect the messenger rules will undergo further modifications in time, for instance reducing the available dice over longer distances.

Activations are dynamic. For each command a token should be placed in a bag or stack to allow for random activations. Ideally this would be a token with the clans Mon (or symbol) on it, but could equally be coloured dice or chits, a stack of cards, etc. Anything that lets the players randomly allocate command activation. Players will draw a token and whichever general that token belongs to can allocate it to a command within the army. That command then activates and performs its actions, then the next token is drawn and the process repeats. This means play can alternate back and forth between the players, or may result in one player having a run of a few activations then the other player having the same. Each command can only activate once per turn.

Kamon Symbols of Japan — Encyclopedia of Japan
The Mon of some of the better known clans in the period, this would appear prominently on banners and screens for the clan’s troops. Some of the clan names in this graphic are non-standard renditions, such as Mouri (Mori) and Houjou (Hojo).

Once activated the command rolls a single d6, adding the appropriate Authority modifiers, and that will give the number of orders that can be given that activation. Orders can then be allocated out amongst the units under command to move, engage in combat or rally. There is no limit to the number of orders that each unit can have assigned, up to the total allocated, but those units receiving a large number of orders will have to take a morale test and on failure become fatigued and unable to take any actions the following activation.

Once all the orders have been allocated, or the player doesn’t wish to allocate any more, the activation ends and the next one is drawn. Once all commands have been activated, the turn ends and the cycle begins again.

Movement

This relates to how the units actually manoeuvre around the battlefield. My plan is to keep movement fairly simple. The distance of movement is the same for all units, though certain units will be allowed an extra move such as mounted generals. I’m generally assuming the unit of movement will be around a base width, as that’s usually a decent indicator of unit and table size. Each unit will have a front quarter, a rear quarter and two flank quarters, with the boundaries extending in diagonals from the unit’s corners. When I say something is n Movements, it means n units of whatever the movement distance is. To make a movement a unit will be issued with a Move Order. This will allow them to do one of three things:

  • Move directly into their forward quarter by up to 2 Movements maintaining facing. This may include charging into contact with an enemy unit.
  • Fall back into their rear quarter by 1 Movement maintaining facing. If this is given to a unit in combat they must take a Morale check after doing so.
  • Change facing to a different quarter and make up to 1 Movement in the new direction of facing. This covers all manoeuvring, whether it be changing facing and remaining in place, or moving in a new direction.

Units may be issued any number of Move Orders so long as the commander has Orders to allocate and they begin the orders within the Command Radius of the commander.

Terrain will have some impact on movement, essentially difficult terrain will only allow one Movement forward rather than two and roads allow an extra Movement when going forward or back along it. These rules still need a bit more experimentation. It may be that difficult terrain ends all movement for that unit for that activation and they cannot be given any more Move Orders.

Charging Mounted Samurai
Massed cavalry charges were rare in Japanese warfare of the period, but small groups of mounted samurai could turn the tide of battle when striking the right place at the right time.

Given the fixed distances, the rules as written could be easily translated to a square or hex grid. I’ve been playing out test games on gridded notepaper (mostly because it’s all I have to hand with everything packed away to sell our house) and it’s worked reasonably well, but overall the fluidity of free measurement will provide a much more satisfying range of movement options.

Ranged Combat

There are two types of combat in the game. The first, and generally less effective, is Ranged Combat. This represents the proportion of bows and guns within a unit. While bows and guns of the period had a theoretical range of 300-500 metres, in reality the effective range against armour was around 50-100 metres. Over time as the proportion of guns increased, firepower became more effective, but was still primarily used as a means of defence, behind screens and fortifications, or for softening up an enemy before the charge into melee for offensive actions.

Standard Ranged Combat will work as an exchange between two units at a range of 2 Movements or less. Most units will have some means of firing, even if its just a few samurai with bows and guns. There will be modifiers available to units, typically ranging from -2 to 2 that can reflect the proportion of guns and firing capacity. In a Ranged Combat exchange, both units will roll their ranged attack dice, hitting on 6s then total up the number of hits inflicted. The default number of attack dice is four, though the modifiers mentioned previously along with a few other special conditions (e.g. firing up a hill would be -1, while firing at close range would be +1) can modify these dice up and down.

Any side that receives at least one hit must make a Morale test, which will be described later but essentially consists of throwing four dice (+/- modifiers) with at least one 6 needed for a pass. For each additional hit past the first one in the Ranged Exchange, a dice is removed from the Morale test. So if a sonae of the Ouchi engages a sonae of the Mori in a ranged attack, both players would roll their attack dice. If the Ouchi rolled three 6s and the Mori rolled one 6, then both sides would be required to take a Morale test, but the Mori would do so with 2 less dice than normal due to the two additional hits.

Failing a Morale test from a ranged attack results in a unit status change. A unit that is fresh and in good spirits will become Wavering, which will somewhat impair their ability to fight in Close Combat. A unit that is already Wavering will become Brittle, which impairs them further still. A unit that is already Brittle will break and be removed from the battle. This means a ranged exchange is unlikely to cause serious damage unless a unit is already in dire straights. There will be a Rally mechanic described later to remove these statuses.

Ranged Ashigaru
Most ranged combat was done by sub units of Ashigaru peasant soldiers armed with matchlock “teppo” guns and light weight long bows known as “yumi”, though samurai would often have guns and bows as their primary weapons well. Indeed the yumi was the traditional primary weapon of samurai in earlier periods before massed peasant infantry and firearms became the norm.

Exceptions to this standard exchange are when engaging from the flank, in which case only half your attack dice can be used, or from the rear, in which case only one attack dice can be used. There is also the possibility of Opportunity Fire, the exact details of which are still under review, but will generally allow a unit to take unopposed pot shots at anyone entering firing range. I’m still not entirely sure on this given the exchange nature of standard firing, it’s mostly a means to prevent units skipping along the front of the enemy without consequence, but I may instead implement some form of Zone of Control on movement that prevents this instead. The other type of firing is Closing Fire, which I’ll cover shortly as part of the Close Combat exchange.

Close Combat

Close combat consists of up to four phases, Charging, Closing Fire, Melee and Shock. Charging is covered under the movement rules and is a movement that ends in contact with an enemy unit. The unit that initiated the charge will gain an extra dice in the first round of Melee. If a unit is Wavering it must pass a Morale test before charging and a Brittle unit cannot charge at all.

The defending unit may choose to use Closing Fire, that is an unopposed ranged attack, i.e. only the defender rolls their attack dice. If it is successful in hitting the charger, and the charger fails the Morale test then the new status is applied, the charge will be cancelled and the charger will fall back or pull up 1 Movement short of the enemy unit. However, if the charger is unharmed, the defender will have one less attack dice to use in the following round of Melee combat. This is to simulate the delay in bringing up the melee troops while firing at the charging unit.

The Charge and Closing Fire occur as part of the normal cycle of Orders, but Melee doesn’t occur until the end of the Activation. This allows all movements and ranged attacks to be carried out first, then all close combat will be resolved.

The Melee Phase involves both participants rolling their attack dice, modified as needed, with different results depending on the outcome. If both units fail to make any successful hits, then each will fall back 1 Movement to their rear quarter. If this movement is blocked, for instance by another unit or a terrain feature, they must instead take a Morale test and apply the appropriate status if failed. If both units make the same number of hits, they remain locked in combat and nothing else happens for them until the next time one of their commands is activated. If one side manages to make more successful hits than the other, that side is considered the victor and may move onto the Shock Phase.

The Shock Phase is representative of the elite troops, such as the samurai, exploiting a weakness opened up by the melee and rushing in to try and destroy the enemy command. In the Shock Phase the victor rolls their attack dice modified by any shock modifiers they may have (typically terrain affects the impetus of the shock phase more than the melee) with the outcome depending on how many successes they have.

With one success the enemy unit is destroyed but the attacker is Fatigued.

With two successes the enemy unit is destroyed and the attacker is not Fatigued.

With three or more successes the enemy unit is destroyed, the attacker is not Fatigued and gets a bonus order to use immediately.

The number of orders may increase with increased success, to be confirmed, and the destruction on one success might be too powerful, so one success may apply a status while two success destroys, etc. These are details to be ironed out in play testing.

Artwork of battle
Combat in the period often ended in bloody and brutal close combat.

Where multiple units are engaged, all dice are rolled together. This is the most “bucket o’ dice” part of the rules, but means large engagements can be dealt with quickly, and makes multi unit melee combats very dangerous, especially if Commanders are involved.

Flank and rear attacks also behave a little differently. There is no Closing Fire when attacking a flank or rear of the unit, and the defending unit cannot use a Shock Phase if it is engaged to the flank or rear, instead if it is victorious in the Melee Phase, the attackers both fall back 1 Movement. This is because an attack at a weak point of the formation would usually be reinforced by the samurai core of the unit, meaning they’ve less momentum to carry out a destructive counter attack immediately and instead just drive the attacker off. Any unit attacking the rear gains an additional attack dice as well as that was usually the weakest point of a formation.

Morale

As mentioned in previous sections, each unit will have a certain amount of Morale that it can use to show how resilient it is to breaking. All units have the same potential Morale statuses, Wavering and Brittle, though how those statuses affect different areas of the game will vary. Morale tests are called for in a number of circumstances where the resolve of the unit needs tested. Morale tests behave the same way as other tests in the game, a number of dice, four by standard, are thrown with at least one 6 being required to make it a success. Some units may have Resilience modifiers that can increase or decrease their morale dice, and having the Army General within range can provide an extra morale boost too.

One of the orders available to a commander is a Rally Order. With this a unit that is not in attack range of an enemy unit (i.e. typically 2 Movements away) and within the Command Radius of it’s Commander, may perform a Morale test and if successful, can reduce their negative statuses. So a Brittle unit that passes it’s Rally Morale test will become Wavering, and a Wavering unit that passes loses the negative status and returns to being fresh and ready for action.

Facing this sort of devastation would shake the morale of even the loyalist of samurai, let alone the peasant masses.

There are still some balancing tests needed with morale, for instance having the presence and loss of nearby units impacting the roll or requiring additional tests, but for the moment I’m keeping it reasonably simple.

Other Considerations

There are a few areas that still need some thought and consideration. I’m still testing out various options for moving through and fighting over different terrain. Given the varied landscapes of Japan I don’t want this to be too much of an imposition, but certainly particularly rugged ground should impose some limitations and fordable rivers appear in a fair few battles of the period so they are important to consider too.

Defensive works is another area that needs some thought. It was quite common for armies in the period to entrench into a defensive position, especially as the ratio of guns increased in armies allowing them increased concentrations of fire. This is definitely something I want to include, either as fixed terrain pieces on the battlefield or as a “dig in” option for a unit. I need to do some more reading on this before deciding how to represent them though.

Assaulting a defensive line
Defensive works were commonly employed on the battlefields of Japan, often made from bamboo or bundles of reed mats. By the later period, concentrations of firepower would make assaulting such defensive works head-on suicidal.

Beyond that there are a number of special rules and traits I want to include. I’ve already got an outline of many of these as a means of conferring special abilities on Generals, Commanders and individual Clan units. I want to be reasonably cautious with these to avoid it becoming a bit too video gamey or “Hollywood”, but I do wish to include some means to highlight leaders who stood out from their peers through tactical or strategic brilliance, or lack thereof, as well as clans that specialised in particular types of combat or weaponry, or were particularly loyal and devoted. There’s also some consideration to be given to the numerous sects of fanatic warrior monks throughout the period and peasant rebellions. I’m not focusing too much on these until I’m completely happy with the core mechanics, though have plenty of ideas for how they could work.

Formations is another thing that needs more consideration – both the individual makeup of the sonae and how they organise themselves internally, as well as the larger formation of the entire army. For the sonae themselves, different formations may confer different sets of modifiers, for instance aggressive or defensive formations, or those focusing on concentrating firepower, while for army wide formations, I’d be inclined to leave them up to the whim of the players as if I get things right they should “just work” as they were intended given the way the battles play out. We shall see!

Beyond that I’ll want to consider some “meta” play around a campaign system, or some means of playing linked battles, as well as some strategic considerations around scouting and espionage that may aid with deployment and game set up. The idea is allow for both historical battles and ones of the players own devising covering various possible scenarios from a straight up fight, through defensive actions or taking of key objectives. I’ve not decided if I’ll look at sieges or not yet, though castle assaults were a common feature of the warfare.

Battle Report

This is one of my pencil and paper test games played out on gridded paper to try out some of these core mechanics. In it, the fictional Maru (circle) and Shikaku (square) clans engage in a clash for control of a key river crossing. I rolled for random entry points across the game area rather than having everyone come in from opposite sides, this felt natural given the mustering of troops tended to involve calling in subject clans. Each army consists of three divisions, marked 1, 2 and 3, so for the purpose of this I will refer to them as the divisions as Maru-ichi (in the south centre), Maru-ni (north centre) and Maru-san (north west), then Shikaku-ichi (west centre), Shikaku-ni (south east) and Shikaku-san (north east). The notations is as follows:

Gm = Mobile General (bonus to movement and attack, negative firing)
Ge = Encamped General (bonus to everything, messengers but no movement)
C = command sonae (bonus to everything)
X = normal sonae
F = firing focused sonae (bonus firing, negative melee)
M = melee focused sonae (bonus melee, negative shock)
S = shock focused sonae (bonus shock, negative firing)
f = fatigued
w = wavering
b = brittle

Hopefully the hills, forest, river, stream, bridge and marsh are self explanatory. The position of the number indicates facing and the negative number on commands indicate lost units.

In the opening turn the Maru-san clan attempts to skirt around the Shikaku-ichi position to link up with their General, however they soon come in range of the enemy gunners stationed on the hill.

In the south, the Maru-ichi General moves to fortify a hill opposite the Shikaku position. Meanwhile the Shikaku-ni clan rushes towards the bridge to seize the objective and support their allies. In the north the outnumbered Shikaku-san clan attempt to secure their flank on the forest and present a line of attack to funnel the Maru-ni enemy into.

The Maru-san find themselves pinned down by enemy fire as the Shikaku General brings his troops to bear on their slow advance. Feeling the pinch on their flanks the Maru-san turn to engage. In the north east, after several exchanges of fire, an impetuous rush by a Maru-ni daisho drives some of the Shikaku-san from the field, and feeling the potential for encirclement growing, the Shikaku-san pull back into a better defensive position.

Not wishing to relent on the pressure, the Maru-ni keep pressing the beleaguered Shikaku-san, while the unopposed Shikaku-ni set up a solid defence between the stream and river. Frustrated by the fire from the hill, the Maru-san charge the Shikaku General’s position. The Shikaku-ichi manage to stall them at the foot of the hill, but the Maru-ichi take advantage of the exposed southern flank of the Shikaku position and storm the hill from there.

Attacked from multiple sides the Shikaku-ichi begin to collapse and the General abandons the camp and flees for the defensive lines of the Shikaku-ni. However, the Maru-ni advance crushes the Shikaku-san in the north and begins to sweep down towards the open end of the Shikaku-ni position, while the rest of the Maru forces begin their advance towards the stream.

The Shikaku fall back over the bridge, hoping the choke point will let them wear down the enemy, but the Maru forces sweep in from all sides.

The assault on the bridge begins and while the Shikaku forces put up a brave fight, they are now heavily outnumbered by the Maru attack.
In an epic clash, the elite shock troops of the Maru-ichi break the bridge defence while the constant fire exchange across the river wears down and eventually breaks several of the Shikaku defenders. With his army broken and troops fleeing the field, the Shikaku general signals the retreat and slinks off the field in disgrace. The day has gone to the Maru, and they have secured control of a vital point between the rival lands.

This was a lot of fun as a game, the narrative flowed easily from the mechanics and while there were a few points were I had to tweak bits or come up with rules for things on the fly, it really helped me refine down some of the mechanics, and determine what did and didn’t work.

Summary

To conclude, in this post we covered:

  • Command and Control: the role of commanders and how the dynamic activation and order system works, as well as the role of messengers on the field.
  • Movement: how movement is determined and the different types of movements available.
  • Combat: both ranged and melee combat and the opposed roll system they use.
  • Morale: how units test for morale and rally from their various states of disorder.
  • Discussed other areas for expansion and thought once core mechanics are settled.
  • Finally finished with a pencil and paper test game and report on how it went.

I’m not sure what my next post on this will be, as the next stage is probably play testing and refinement, then looking at some of the special rules. No doubt you’ll see some Feudal Japanese forces creep into my painting queue in the coming year in 3mm, 6mm and/or 10mm, along with some more test game battle reports.

Thoughts and suggestions are always welcome, I’ve only been in the hobby a few years and don’t have that many games under my belt, so any pitfalls or glaring omissions I’d be interested in knowing about, so please share!

As ever, thanks for reading,

Matthew

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