Napoleonic & ECW wargaming, with a load of old Hooptedoodle on this & that

Monday, 30 May 2022

WSS: The Delicate Matter of Interpenetration


[Nurse - the screens...]

From my recent playtesting game with Ian, we ended up with a note of about 12-14 points in the rules which needed some change - or at the very least some reconsideration. Well and good. That is what the game was about (apart from the social delights), and it had gone well enough to encourage me to get on with thinking about what, if anything, needs to be done.

One area of the rules with which we had some problems (i.e. for which we found we were making things up as we went along, to cover holes and clunky bits) was that of interpenetration. I realise that this gets us into all sorts of disagreements about definitions, so I shall skip lightly over that, and also I shall continue to avoid reading drill manuals, other than the references summarised in the works of Chandler and Nosworthy.

By interpenetration (which is a vague word, but I hung on to it because it affords me some adolescent amusement), I am broadly covering the matter of troops passing through their friends, and in two situations:

(Type 1) voluntarily moving through friends as part of ordered movement

(Type 2) moving round, through (or over) friendly troops when retiring or routing

Since plagiarism is the most sincere demonstration of respect (which is why I am pleased to be so widely respected on TMP), I did a lot of reading, especially of prominent rule sets, some for periods which were not entirely relevant. I looked at, among other sources:

Beneath the Lily Banners

Piquet's Field of Battle (3rd edition)

Black Powder

The Twilight of the Sun King

Polemos's Obstinate and Bloody Battle

Honours of War

Charles S Grant's updates to The War Game Rules

and I got a lot of useful information online - in particular from the excellent Rod's Wargaming blog. I also revisited For King & Parliament, and I have the rules for Tricorne, which is the AWI member of the Commands & Colors family.  

A lot of excellent stuff here - some of it made more or less suitable for my purposes by the underlying game scales, but all of it the product of very sound reasoning. Impressive.

The thing which surprises me is the frequency with which these experts appear to disagree about how such things worked, and even the extent to which they did work. I am not going to produce a table of differences or anything, but the view seems to range from units being able to move freely through each other without delay or disruption (provided they have sufficient movement allowance to get clear of each other) to much more restrictive approaches.

In particular, Field of Battle's basic approach to the topic of Type 1 (voluntary) interpenetration is very detailed and pretty liberal, and I always take very seriously the way the Piquet games are thought through and researched, but in the period-specific section for the WSS it says that such voluntary movement is not permitted, except through deployed artillery batteries. This came as a bit of a surprise, and further reading got me into online debates about whether there should even be such leniency towards moving through artillery - a couple of writers expressed strong views that batteries took up more room than is normally assumed, and that the idea they were mostly space is incorrect because of the crowd of support wagons and limbers, not to mention people racing about with ammunition. I suspend judgement on the porous nature of artillery, then - for the moment. There are a lot of very earnest people out there. Bless them all.

I'm somewhere at the start of a dialogue with Ian about what we learned and what he thinks of my thoughts for changes, plus ideas of his own, etc, so none of what follows is intended to pre-empt any of that discussion, but I'm sketching out some thoughts - mostly prompted by the wide range of opinions elsewhere. I must also emphasise that my priority is to produce a game which is enjoyable and which runs without hitches, rather than to reflect the inspired detail of military thinking at the start of the 18th Century, but it must bear some resemblance to what really happened!

It seems to me, after all this private study, that the fundamental principle of military theory at the time was to prevent the enemy's lethal units of Horse getting around your flank, or breaking through any gaps in your line. Squares were almost unheard of, except in odd instances where a single unit might be isolated somewhere, so the ideal was an unbroken line, from horizon to horizon, the only discontinuities being strong terrain features or built-up areas. The second line of units might have intervals, but never the first; it was an established fact that cavalry could not defeat formed musket infantry attacked from the front, so give them nothing but front to attack.

This means, I think, that the spaces between units which I have claimed, in other periods, give room for routers or reinforcers to pass through were virtually non-existent.

Early days yet, and this is a sketch, but I'm thinking along the following lines for the Type 1 (voluntary) interpenetration situations (note that my game uses hexes, but the principles should hold good in any event):

* Friendly (march) columns and limbered artillery may move freely through or past each other, and any troops at all may pass through friendly unlimbered artillery, but in both these cases they must have enough movement allowance to avoid ending up in the same hex, and may not come into contact with the enemy while so doing.

* Friendly lines which are adjacent, parallel and either one behind the other or directly facing each other, if both are given orders to do so, may exchange places, provided neither of them is in contact with the enemy at any point of the manoeuvre.

And that might be about it for Type 1.

Type 2 needs some more detailed thought. Despite its pretty strict view of Type 1 interpenetration in the WSS, Field of Battle allows routers to pass through (leapfrog) anyone behind them, there seems no limit to how far they can jump, but they have to keep going until they are clear of the rearmost. I'm not keen on that at all, not in a system of units with no gaps in between.

Ian and I prefer a version where retreating units may push a single unit back, without upset to either party, but if this is not possible without pushing back a second unit, or if impassable terrain (or the enemy) gets in the way, then they have to take any extent of the required retreat which they are unable to comply with as losses. Yes, this is very like Commands and Colors - well spotted!  

I'm still reading and thinking - any helpful ideas will be very welcome - any prepared lectures on the full procedure for Passage of Lines will be less warmly greeted - I've done a bit of that this week!


  1. It is hard to offer a meaningful comment when you have obviously devoted a considerable time to reading and thought into the matter. I do think, though, that one has also to bear in mind the scale of the action you want to depict.

    I have an idea that a second line was drawn up to allow gaps (intervals) to allow the first to pass through should it suffer a reverse. That suggests to me that maybe the second line was drawn up in columns, at intervals sufficient to form line once the friends have passed through.

    Although that seems plausible, one does wonder if the second line drawn up that way would have time to form line. Especially if the first line had been defeated by cavalry.

    Apart from that, I believe that the passage of lines could not have been carried out under fire.

    In my own rule sets, I never insist upon a morale check for a unit 'seeing' another in rout (or retreating in general). Apart from any other consideration, one has to ask: what are NCOs for? However, it is a different story if the routers pass (burst) through a friendly unit. There seems to me a very strong chance that the friendly unit would be carried off as well. They would certainly be disordered.

    On the matter of artillery lines, one is led to ask, where were they deployed at the outset of the battle? Usually in front, I would have thought. If the army had it in mind eventually to advance, the horse and foot would have to move ahead of the gun line. What, then, is the gun line doing?

    From my VERY limited researches, I take a gun battery to occupy roughly 27 yards (25 metres) per 2-gun section. As the pieces themselves are 6-ft (2 yards/ 2 metres) wide one is left with 23 yards/ 21 metres of 'empty' space occupied by the section.

    Is that space occupied by other impedimenta? I rather doubt it. I'd be more inclined to expect whatever vehicles are needed are lined up in a column behind the pieces. What's not needed for the battle is held well back from the battle lines. That the intervals between pieces are so wide may be precautionary, but also allow for a certain flexibility when coping with accidents of terrain. But it also suggests there might have been some method by which passage of gun lines might have been effected without much inconvenience - provided the enemy were far enough off. It seems likely enough the battery itself would be preparing (would have prepared) to move, clearing the intervals for the passage of foot of horse.

    I might mention, by the way, the method suggested by the Praecepta of Byzantine Emperor Nikephoros Phocas (c963-969CE). The infantry were formed up in blocks to form the front line. Between the close-order blocks were intervals of a width sufficient to permit the outward and inward passage of the cavalry. The infantry were the holding force, and acted as a species of fortification from behind which the cavalry could lash out, and withdraw as occasion allowed.

    I mention this as an early example of the 'passage of lines', though of course, it might not have a direct equivalent in the 18th century.

    I don't know whether I've added anything useful, apart from expressing my own thoughts upon the matter.

    1. Ion – thanks very much for taking so much trouble to set out your thoughts in this way – I appreciate this very much.

      I’ll attempt to set out some form of response, based around the order of the points you made. I am, to a large extent, still “thinking aloud” (in writing, of course!). I was aware that this post was going to be pretty heavy going, so tried to keep it short and tried to avoid simply blurting out my entire rule set in one big heap of spaghetti. However, as you say, so much of this depends on the size and style of the game, and some of my rule systems are built around my wish to cope with large actions, and to keep the level of detail appropriate to this. My game also reflects the fact that, artillery apart, armies could not physically hurt each other very much until they got very close together.

      Thus my first bit of blurting is that I must explain that my hexes are about 200 paces across, which is much further than effective musket range, and thus – in rather boardgame-like fashion - units can only fight each other when they get within 1 hex of each other. I do not distinguish between the classic shooting and melee activities. As far as I am concerned, there is just one kind of fighting, and I call it Combat [I can feel a Nobel Prize coming up here]. The assumption is that for the most part infantry combat will be fire-fighting at short range, and cavalry will be hacking at each other with swords, but what they are actually doing to each other is rather beneath the General’s view. Combat. OK.

      I use a standardised unit size for all nations, so all units will have a front of something approaching 200 paces in line, and 1 unit per hex works nicely with that. I agree entirely that there would be gaps in the second and subsequent lines.

      I don’t think there was any element of Ordre Mixte about the set up. Anyone in column would be a fair distance from the fighting. From my reading of Chandler and Nosworthy, and from what was explained to me by Chris Grice, the author of the Polemos WSS rules, armies approached the enemy in columns – normally to the left of their intended position, for some reason - and wheeled right to march across the enemy’s front. The leftmost column would be the intended front line, the next one to the right would be the 2nd line, and so on, and they would plod along across the enemy’s front (at a reasonable distance, I guess), eventually performing a “quarter turn” to their left to form line when they got to the designated position – which must have required a bit of rushing around to get the officers and the colours in the right places. This is not a quick process – painstaking – especially in a period when there was no cadenced marching. I have a cartoon vision of detailed maps and of men with surveying equipment! Thus a picture builds up which has all marching in columns and all turning into line at a safe distance from the enemy. Thereafter the units, with gaps as necessary in the 2nd and subsequent lines, would do all their manoeuvring into action in a series of lines.

      Yes, agreed – ponderous. [since Blogger doesn't like the size of my reply, I shall continue in a separate reply...]

    2. [continuing...]

      Because of my game “view” of the scale, I allow units further than 2 hexes from the enemy to move a little quicker than those closing in for a fight. For a brief period (the most recent revision) I reluctantly introduced an element of explicit morale into the game – units could become “shaken” to various degrees in addition to the other things which could happen to them. This seemed like a sensible (even a traditional) approach to wargaming, but it seems probable that I’m going to take this out again, however heretical that may seem. The new Shaken rules added another colour of counters to the table top, and another layer of admin and things to fret about and test for, and in practice added very little to the game otherwise.

      Game philosophy point for my rules coming up: units in action will take “hits” – losses of what other rules call Combat Effectiveness – this represents casualties, confusion, loss of conviction, control and confidence (the 5 C’s). These are the black counters in my game – when the number of black counters for a unit reaches its initial strength (I call this “Status”, which is a rubbish name but has been in use for long enough to become somehow part of the system), the unit is broken and removed from the field. In some circumstances, a unit may rally away some of its hits (never the first one), but once they are gone they are gone. I have no wish to track the adventures of routers across the field – once the Status has fallen to zero they are assumed to have lost interest, and they are airlifted out – I do not care where they have gone. Their General will care deeply that they are no longer fighting, though.

      The other result of combat will be retreats – the units are pushed out of position, which is a nuisance all round, and the time taken to move them into position is lost. More orders and more time will be taken to bring them back or replace them.

      So the morale is present in the black counters bit. It turned out that the (yellow) shaken counters added nothing but labour to the game, though there might be an argument that it improves realism in some way. Whatever, though it took some thought and some effort to introduce the yellow counters in the last revision, I have come to the opinion that they add nothing which is not taken care of by the black counters, so I shall remove them with few pangs!

      Artillery. In my Napoleonic games I like to use batteries of 2 gun models. Partly this is because it looks better, but it usefully gives a more definite direction of facing – batteries tend not to pirouette gaily on the spot – at least it is more obvious when they do. For my new, toy-soldier WSS game I was happy to go with more traditional 1-gun batteries. I am satisfied that the overall frontage of one of my vanilla, all-nation batteries would be near enough 1 hex, and there would be spaces in it, but a single gun in a hex does, admittedly, suggest that the amount of space is very generous. One interesting feature of my rules is that the move allowance of a unit of infantry in line, when near to the enemy, is just 1 hex, which means that they are unable to march through a deployed battery and get clear through the other side (as required) in one turn. They can do it when they are further away, however. The implications are probably pretty obvious, but it means that any clever marching through artillery had better be some distance away (more than 400 paces from the enemy). I’m still thinking about this…

      That’s probably more than enough to be going on with. Again, many thanks for your thoughts.

  2. Sounds like you've got a sensible compromise/solution there Tony. Personally for Type 2, I'd go for any routers passing through an infantry unit in line, cause disruption to the unit they're passing through. Any subsequent contact by an enemy unit catches the disrupted unit at a disadvantage. I say infantry because I think cavalry squadrons may have been in checkerboard formation. Perhaps.

    1. Thanks for this Chris. Since I'm going to remove the "Shaken" concept (for better or worse), the disruption is likely to be being pushed back or suddenly being exposed to the enemy. Maybe in some circumstances the support line might take a "hit" to reflect this. Hmmm. That might do it.

  3. I think the rules for Type 1 are covered. Type 2 is more difficult and I find it frustrating that for WSS and even Napoleonic’s that although plenty has been written and the battles and tactics there is very little information about battlefield management. If the armies deployed in 2 or 3 lines then there must have been some mechanism to reinforce the front line but how? Logic suggests that swopping units around when engaged in combat would be difficult unless both units had superb discipline but perhaps there was some way this was done - maybe during lulls in the combat?

    I’m still in favour of push backs rather than swopping as a way to represent one side getting the upper hand. The alternative might be to allow swopping of a unit in contact with the enemy with a supporting unit if they expended 1 order each and there was a 50% chance of either unit taking a hit in the process?

    1. Hi Ian - Thanks for joining in here. I think (or have always assumed) that there was enough space between units - especially between Napoleonic attacking columns (unknown in the WSS) - for routers to stream through the cracks ("like rainwater through a grating" - DofW). It seems reasonable, but it is very convenient, either way! In the footnotes to one of his games (probably Grande Armée) Sam Mustafa says something along the lines of "tracking where a routing unit is doesn't help much - effectively they are nowhere - just a crowd of men looking for spaces to get through to escape". [Perhaps it was Doc Monaghan Snr who said it, now I think about it...]

      I'm still scratching my head about this. If the WSS situation was deliberately a row of deployed units presenting an unbroken line, without the intervals filled with skirmishers typical of later eras, and if my tabletop has the supporting line in the next hex back, approx 200 paces apart (which seems to accord with the sort of spacing which David Chandler describes), then where do any retreating units go to? - and as you say, how does anyone else replace them?

      Maybe the systems in my rules offer a possibility: if a unit of infantry is forced to retreat from combat, then if there is a space behind them they can retreat into that, if they have to push back the guys behind then maybe that's fair enough too, but, either way, a gap should now have appeared between the two sides in the combat. If there are two units suitably positioned at this point, then in the next turn they may be ordered to execute a Type 1 exchange of places, as discussed, since they are not adjacent to the enemy. If the enemy has followed up, of course, then they are in trouble...

      Thanks for this. I also spent a little while looking for descriptions of retreats in the very few eye-witness accounts of the WSS I have here. They don't talk much about their own retreats, and seem to have little detailed idea of where the enemy went if they broke - mostly smoke and a few casualties left. [In passing, a few of the British memoirists devote more space to describing the glorious adventures of the D of Marlborough than to what they actually saw themselves! Maybe there were brownie points to be had?]

      Cheers - T

  4. I had a shufti in Nosworthy's British drill booklet for an answer to the interpenetration problem. Apparently Doubling the Files was the common practice; alternate files moved back and took station behind the file to their left, thereby doubling the formation from say, three to six ranks, then the files are closed up so a gap is formed on the flank(s) for the unit(s) behind to go through. Sounds quite a complicated process, especially if your battalion is under some stress, but I suppose it would have been well-practised if it was a common occurrence. I imagine the same process could apply to battalions wishing to fall back through their supports - would be a bit touch and go if the enemy are on your heels, but did anyone react that fast to what the enemy were doing in WSS?

    1. Crikey - that's impressive - thanks Chris, that's brilliant. I also saw something somewhere that mentioned doing something similar, doubling the files, and other troops could pass through the wider gaps, but I'd be nervous if terrified men with bayonets were doing the penetration. As you suggest, sounds like the sort of thing you would do if you had plenty of time, and things were calm, calm, calm...

      Also would require some co-ordination and agreement between units, to get timing right. I've seen the French drill book listed, but never the British. Suspect I would be asleep by page 6, which is a common problem these days!

    2. All sounds very straightforward in the book, but I couldn't help but think clouds of thick powder smoke wouldn't have helped matters.
      I had a similar thought about the inter-unit co-ordination, especially in coalition armies. What is the Dutch for "I say, old chap, would you mind awfully getting your fellows out of the way for a moment?"

    3. Agree entirely. What astonishes me, really, is that I have waded through Black Powder, Charge!, Charles Grant's rules, Featherstone, Wesencraft, and cannot find a mention of this topic. Hmm - does that mean it shouldn't come up in a sensible game? Does it mean that when it does come up the solution is so obvious that it was considered not worth mentioning? Mystifying.

    4. I think it means that rules writers (me included) have bottled it because we don't know, or quite understand, how it worked in practice. It must have happened, surely, but I can't recall anywhere reading "X regiment fell into confusion while trying to pass through, or by, Y regiment" so, no, best not mention it, it must have been ok.

  5. Always one for a good debate this and trying to compare drill to reality is always a bit circumspect. Given time and space then formation changes and troops passing through one or the other is without doubt more than feasible. The more pressure that is added then the more difficult this becomes still possible but the likelihood of one or the other formations becoming disorganised/disrupted increases.
    Units forced back against friends may indeed push them back or May disorganise both units. Once a formation has lost formation and morale then human nature takes over they are no longer a formation just a mass they will look for gaps and safety anywhere. My view is that inter penetration becomes harder and more likely results in disorder for either or both the more negative factors that are applied ( enemy proximity, loss of morale etc)

    The closest example I can give is when I was a Public order commander one drill we practiced regularly was we had effectively a shield wall advancing towards the opposition, behind the shield wall was the cavalry they would start to advance at the walk, then the trot just before they broke into canter the order was given for the shield wall files to open effectively doubling as described above and the horses cantered through the gaps before moving up another gear. Now I never had an accident even when wooden blocks were being thrown at us but in real combat/ riot situations I’m not so sure, the nerves on the Officers were frayed they were looking front and putting complete faith in the commander to call the order at the right time and everyone snap to it..
    So I guess I’m saying unbroken units can interpentrate but with a risk of disorder to either or both. That risk increases the more engaged they are. Broken units will run for the nearest gap, if there isn’t one then they will look to force their way through a unit to their rear?

    1. Hi Graham - very interesting detailing this sort of procedure - this is very like an old John Keegan book I used to have, where he analysed what happened to the individual soldiers. I can imagine the fear and confusion would create havoc, and if someone was firing muskets at me from 60 yards away as well the I think I would just dig a hole and hide in it! This is the sort of thing I like to think about when I'm cutting lawns or killing weeds, though the threads can get a bit confused at times...