Friday, May 14, 2021

One-Hour Wargames Marengo - Part 1: Scale


Lately, I’ve been reading a lot about the battle of Marengo. It’s a fascinating, if baffling, subject: several crucial aspects of the battle are very different in all reports I’ve found, including first-hand accounts. On top of that, when reading primary sources, one has to wade through several layers of self-aggrandizing revisionism by First Consul Bonaparte, complacent revisionism by his clients, and scornful revisionism by officers who deemed their achievements deserved greater rewards.

After deciding (somewhat arbitrarily, of course) which sources are most reliable, it’s possible to start putting all the pieces together. And the truth slowly emerges: what goes under the moniker “Battle of Marengo” is in fact a long, tragicomic series of SNAFUs and blunders by both sides over the course of at least two days.

In his fantastic blog “Obscure Battles”, Mr. Jeff Berry provides a very colourful and eminently enjoyable AAR:
Obscure Battles: Marengo 1800

The online magazine “War Times Journal” has a very nice page on Marengo which includes several primary documents:
The Battle of Marengo (

There are of course countless more reports and webpages devoted to Marengo, I’ll just link a few more among those most useful to wargamers here:
Battle of Marengo (
Jean Lannes » Marengo
Journal de voyage du Général Desaix, Suisse et Italie (1797) : Louis Charles Antoine Desaix de Veygoux , Louis-Charles-Antoine Desaix, Arthur Maxime Chuquet, Arthur Chuquet , Arthur Maxime, 1853 -1925 Chuquet : Free Download, Borrow, and Streaming : Internet Archive

Speaking of wargames, there are several published wargames on Marengo; my favourite ones are those (the fact that both use blocks is probably not a coincidence):
Battle of Marengo | Command Post Games
Bonaparte at Marengo | Board Game | BoardGameGeek

…but reading primary sources left me with a desire to experiment further with alternate course of actions and “what-ifs”. The simplest thing would probably be to modify Pub Battles’ Marengo official scenario and terrain rules to make both closer to primary sources. However, I’m a total rule nerd and I really enjoy designing simple wargames, so I started to reconsider everything from scratch instead. My vague design attempts quickly took a very specific direction: I wanted to jot down the simplest, fastest possible set of rules which would still give a broad picture of the tactical situation and Marengo. A logical place to start was thus the (arguably) simplest wargame I ever played: Neil Thomas’ One-Hour Wargames.

One‑Hour Wargames Marengo?

Is it at all reasonable to expect OHW to be able to model a ‘real’ battle like Marengo? Well, let me start with a categorical syllogism.

Major premise: Neil Thomas’ One-Hour Wargames, rules-as-written (RAW), give simple - but fun - Horse & Musket games focusing on small tactical exercises (scenarios) involving a handful of units. There’s a surprising tactical depth to be found in play, and the overall narrative is strikingly similar to what more ‘serious’ rulesets model given the same situation.

Minor premise: Realistic battlefield situations/historical scenarios can be regarded as the sum of many simultaneous, smaller tactical exercises similar to OHW’s scenarios.

Conclusion: It should be possible to play historical scenarios/full battles with OHW.

…however, after trying to condense the Marengo situation into a typical OHW scenario, I’ve found the result was so bland and generic as to feel utterly disconnected from the original historical event. There’s a number of problems involved in using historical OOBs with the RAW; so I wrote a set of amendments, which I’m currently playtesting with an ad-hoc created Marengo scenario. They seem to work! In this series of posts, I’ll dissect what I amended, how and why. At the end of the series, I’ll compile all the amended rules into a coherent (I hope) document.

Let’s start!

Step 1: Start with a great map.

Given my Kriegsspiel-inspired, map-and-blocks obsession, Marengo is a great choice: there’s a wonderful historical map available on the web – one of the very rare ones which doesn’t show troop positions and can be thus played upon without any kind of image processing. It’s the same map Command Post Games used as the basis for their Marengo game, and you can consult a copy at Simmons Games [edited to add - unfortunately their website seems to be down since a few weeks, I hope everything is fine]:

The map is wonderful, but it has a few quirks if you study it carefully enough.

For example, most people first playing Command Post Games’ Marengo are driven mad by the fact that there seems to be a major alley on both sides of the Bormida between Cascina Bianca and La Moglia – but apparently, no bridge or ford. Conversely, there seems to be some sort of crossing marked out near Montecastello across the Tanaro – but there’s no mention of such in historical accounts, and it would definitely be a bizarre omission given that it would definitely have mattered.

Moreover, the vexed question about the (alleged?) other bridge used by Ott’s division gets no clear answer on this map. Austrians infamously had a pontoon bridge established on June 13th somewhere downstream (North) of Alessandria, and First Consul Bonaparte assigned Colonel Lauriston with the task to destroy it. Later that evening however, the officer admittedly reported to him that the order proved impossible to fulfil due to staunch Austrian resistance. The problem is, Napoleon later would claim he wasn’t informed about this by anyone, and assumed the bridge was positively destroyed when formulating the plan on the next day – this could explain his famous, subsequent judgement blunder…

Except it doesn’t. Reports are vague and discordant, but if the pontoon bridge was still there on June 14th, then it didn’t play a large part in the battle. And it would be strange for it to be still there, given that it took Ott’s wing so long to cross the Bormida. In fact, there’s a direct mention of the pontoon bridge being unanchored and floated next to the permanent bridge at Alessandria in one of the sources… which also seems strange, given that Austrians would have needed to drag it against the river’s flow. Or is the mysterious dashed line at Montecastello the pontoon’s final position on June 14th? Nobody knows, apparently. As with everything regarding Marengo, all of the above is just an educated guess. Some of the reports contain the same overall narrative regarding – not this extra pontoon bridge – but the main bridgehead in front of Alessandria. We’ll never know who’s right, I’m afraid.

It’s easy to criticize Bonaparte for his initial battleplan at Marengo (or rather, the absence of one). But, as it often happens throughout history, most great military commanders’ plans which hindsight exposed as ‘bad’ did in fact make perfect sense at the time of their formulation (including Cannae, but I’ll leave that one for another time). In this case, just imagine French commanders trying to drive Austrians off Marengo, late afternoon June 13th. Then suddenly Austrians evacuate the fortified farm and retreat – not to their tete-de-ponte, but all the way into Alessandria, across the river. French troopers only stopped pursuing the retreating Austrians when coming into the sights of no less than two full artillery batteries, finally taking positions in the Pedrabona/Pietra Buona farm.

French high command reasoned that the only rational explanation for the Austrians’ course of action was that they had received orders to relocate somewhere else… but in fact, it was a C&C blunder: they were ordered to hold the tete-de-ponte at all costs on June 13th evening! This proved to be a (totally involuntary, but incredibly effective) feint which caught Napoleon completely off-guard on the next day.

The 71-years old Austrian Commander-in-Chief, Michael Friedrich Benedikt Baron von Melas, instead ordered the just-retreated troops to cross the river again in the dead of night – and to do so without lighting any fire so as not to alarm French vedettes. However, there apparently were serious problems in moving such a large number of troopers across the single (?) bridge on the Bormida, and the first morning lights saw only a small portion of Melas’ infantry having formed on the far side of the river.

What I’m trying to demonstrate here is that Marengo wasn’t at all a straight and fair pitched battle, or a contest between high military geniuses at their best. Rather, it was the result of several judgment errors, communication failures, improvisation and blind luck (or lack thereof) on both sides. Due to this, I doubt that any ‘classic’ tabletop wargame, however detailed, could model the whole situation in any meaningful – let alone entertaining – way. I wager something like Engle Matrix or open Kriegsspiel (both requiring an umpire and involving hidden information, random events and roleplaying elements) would probably get much closer to what commanders really experienced on that June 14th of almost exactly 221 years ago.

In contrast, my OHW-based Marengo game will have all the details sorted in advance, and there will be no piece of information hidden to the players or determined randomly at the start of the battle. For example, there will be only one bridge in play – that is, the one at Alessandria. This seems to keep outcomes more closely in line with historical reports.

One might ask however, is it realistic to expect such a simple ruleset as OHW to be able to model anything at all regarding a historical battle? My answer is yes: OHW can in my opinion work as a simple, fast ‘toy model’ of a real battle – provided that you feed it with real values in terms of effectives, space, and time. In that case, I think it should be able to represent a general idea of the situation, give a rough assessment of the possible courses of action, and present players with broad-brush, but historically relevant, choices.

But (most importantly for me), it should give an overall impression of how the entire battle looked like: how much space did a division occupy? How many battalions do you need to defend the Fontanone? Why did take so long for the whole Austrian army to cross the Bormida? I think a map-and-block approach is more suited than using figures to model all of the above, or at least to look vaguely similar to the real battlefield:

One last point about the map: there are a number of open issues regarding terrain and how it impacted on the battle’s evolution. The wineyards were probably of a type that completely impeded cavalry movements along the W-E axis. The Fontanone’s banks were soft and swampy from recent showers and rendered the single bridge at Marengo a lot more important than one might think at first glance. The ground itself wasn’t as billiard-pool-flat as it’s today, after 80 years of mechanised agriculture. All of these issues will be considered in a future post; for the moment, I’m only interested in the general size and shape of the battlefield.

As a first move to reduce complexity, I’ve decided to crop the playing map to a square portion of the battlefield which saw the most intense action, and this is the result (I’ve added a scale in toises in the upper left corner; a toise is around 1.9 metres, and the map covers a locale of around 6.5 x 6.5 kilometres).

Step 2 – Orders of Battle and how to represent them (size does matter).

The next step is to find historical OOBs and to convert it into OHW units. I’m not interested in details and troop types yet – I only want to get an idea of force/space ratios, frontages, etc… which immediately brings to the fore the issue of scale and a ton of practical issues I’ll elaborate on later. Let me explain. Marengo is not a large battle by Napoleonic standards, with around 30k combatants per side. The one reproduced below is a typical XIX century situation map for the battle – there are many of them available online. Judging from their frontages (and their number), those tiny rectangles must be regiments, or demi-brigades, or huge battalions, or any formal classification for a total of around 1500-2500 foot soldiers or around a third that many mounted troopers. It seems to make sense to have these as the actual playing pieces in our wargame.

Now, One Hour Wargames’ RAW are (apparently) agnostic about scale. But no wargame I’m aware of is really scale agnostic – not even those who proclaim themselves as such. Projectile weapons range is where to look first: any kind of specified maximum/effective range for missiles (even if it’s ‘zero’) intrinsically implies a length scale. In horse and musket OHW, infantry and artillery ranges are 12” and 48” respectively – while allowed unit frontages are between 4” and 6”. Even if you assume those figures to correspond to extreme musketry and cannonball ranges (say, around 300m and 1,2 km?) and use the widest possible unit frontage, this equates to assuming our playing pieces represent 150m of linearly deployed troops – that is, largish battalions at most. Of course, if you instead assume those 12” and 48” to represent effective ranges, figures drop by between 2 and 4 times, thus making one OHW unit comprise several companies at most.

With around 60000 soldiers in the battle, it’s easy to see how this is not a viable approach. We need to increase the represented effectives by around 400%, and – consequently – to reduce musketry and artillery ranges by the same token. But I’ll leave the mechanical amendments to movement and firing ranges to a future post; for the moment, let’s just define the size of the ‘chunks’ we’ll divide each army into, both in terms of effectives and actual measures on the table.

As a preliminary consideration, I’ll note that OHW uses inches for all measurements, but it’s trivial to instead use any other unit of measure to scale down (or up) the physical representation of the game on the table, with centimetres being a popular option for ‘pocked-sized’ games. I’ll continue to express all measurements in inches to remain compatible with the RAW, but I’m really meaning generic “OHW length units” instead. I already know for sure that I won’t use actual inches, since at 6” per regiment I’d need half a tennis court to play even on my cropped Marengo map. My amendments will be based on the following sizes/frontages/ranges assumptions:

·       The average frontage occupied by one soldier in a formed infantry unit is assumed to be around 50-60cm

·       The average frontage occupied by one cavalryman in line is assumed to be around 100-120cm

·       Effective musketry range is assumed to be 125m - a broad generalization to include fog of war, inaccuracy… but also the often overlooked fact that even a 5% hit rate is already devastating if you think about it!

·       Skirmishers/sharpshooters are assumed to deploy around 250-300m forward of their parent units, and their shooting to have a longer effective range than massed infantry’s. Due to this, they can start to engage enemies at around 500m forward of a massed infantry unit’s position.

·       Effective artillery range is assumed to be 1000m, extended to 1500m due to bounce in appropriate terrain.

·       Line infantry units will represent a demi-brigade, regiment, huge battalion or equivalent formation comprising around 1500-2500 troopers. Light infantry units represent around half that number, cavalry more like one third, while artillery units represent around two batteries with accompanying caissons, infantry and horses.

All things considered then, I will use a scale of 3 “OHW units” (inches in the RAW) = 125m (or around 65 toises if you are an history nerd like me). This equates to all units having a frontage of 250m.

It’s important to note that, given the above figures, not all of the effectives in a given unit are assumed to be always lined up in a continuous line. The standard 6” frontage of units is intended to represent the space occupied by e.g. a couple of infantry battalions deployed either in line (side by side), or in more compact formations interspersed with the open space necessary to maneuver them effectively. For simplicity’s sake, frontage remains the same for all (implicit) combat formations including ordre mixte and attack columns; columns of route will be represented differently (more on this in a future post).

Formations will not be explicitly represented. It's assumed that officers are constantly trying to keep their men in the most tactically sensible formations; their varying degree of success in doing so is represented by their – and the enemy’s – attack rolls. Regarding line infantry in particular, the assumption is that most of the movement represented on the table is done in some form of columnar formation, e.g. by grand division. Column of route by half company or even narrower are instead assumed for road movement. Infantry units are assumed to deploy into line as part of their firing action (which, as in the RAW, cannot be combined with ‘standard’ movement).

What about units depths then? Well, there are some surprises. The depth of a cavalry unit in 2 ranks is around 6m, and that of a massed infantry unit in 3 ranks less than 2m – both of which are vanishingly small on this scale, corresponding to something like 0,2 inches assuming a 6” frontage! This is practically impossible to represent on the table, even if using the thinnest blocks/counters (let alone miniature bases…). However, as I said above, units are not always assumed to be fully lined up, and infantry in particular will have progressively deeper formations when deployed in ordre mixte, column of grand divisions, column by company, etc… According to this, I will use a default depth of around 50m to accommodate for most non-route formations and/or the space all regiments in successive lines would avoid not to hinder frontliners’ maneuvers. Columns of route, being often 4-8 men walking astride, were basically a line moving sideways, and they will be represented as such (details will follow in a future post).

Artillery is something of a surprise, though. The depth of an artillery battery including reserve caissons was something like 150-200m! This corresponds to a depth of around 4” in OHW terms, which starts to be both non-negligible and practically feasible to be represented on table.

Putting it all together

So that’s what we have so far, in OHW’s native length units (inches):

Unit Type

Avg. effectives



Formed infantry




Light infantry









16 guns



 And that’s what they would look like on the map, at the correct scale. I’ve included examples of all four unit types: French line infantry, light infantry and cavalry units in plausible starting positions for Gardanne’s, Chambarlhac’s, Kellerman’s and Champeaux’s men; plus two Austrian artillery units in their alleged June 13th evening positions.

This is already starting to look like the real thing! One non-trivial issue remains, though: in OHW scale (inches), the map above is exactly 160x160”, an unpractical size for (most?) dining room tables. The trivial solution is of course to reduce the physical footprint of units – that is, making one “OHW unit” to correspond to something smaller than 1”. Centimetres are still not small enough – printing a 160x160 cm map isn’t exactly trivial. Using 1 OHW inch = half a cm is doable, requiring a perfectly reasonable 80x80 cm map and units with a frontage of 3 cm. Myself, I’ve decided to go as small as practically possible, which I’ve found to be only a tad smaller: my blocks will have 2.5 cm wide frontages and my map will be around the size of a typical DBA mat.

In the next post, I will detail my amendments to OHW on the crucial issue of movement and terrain. 

Tuesday, March 23, 2021

"Same chaos" OHW variant: increasing fog-of-war and uncertainty without actually changing anything in the RAW's statistics

A lot of people reading or playing OHW for the first time are left with the impression that it’s a bit too deterministic and predictable. I don’t personally have a problem with that (it’s perfect for a specific style of solo play as I explained earlier

However, I understand it can generate a sense of detachment if one is used to systems with more ‘handles’ and/or bells & whistles. Here’s a perfect description of the phenomenon:

Battlefields and Warriors: Black Powder and One Hour Wargames (

"The OHW combat system can give a generic sense that one doesn't care about their units too much. You push them into action and as they rack up hits (towards the 15 that simply removes them from play), you start to feel 'can I get one more round of shooting out of them before the melt away'?"

The most widespread answer to this is to modify the rules introducing extra mechanisms which make the game more unpredictable. Many players also dislike rosters (again, I don’t have a problem with that, but I understand it might feel clumsy in play).  Here you’ll find some especially clever solutions for both problems:

A modification…or two…of 1 Hour Wargames. | John's Wargame Page (

However, all rules mods I’ve tracked so far change at least somewhat OHW’s RAW result variance or even balance. Since I’ve found that most OHW scenarios are very finely tuned for balance, I’d prefer to find a way not to do that… And I think I’ve found a workaround.

OHW ‘Same Chaos’ variant

You’ll need four types of tokens, labelled “4”, “6”, “8” and “x2”. Every time you attack an unit, put a token corresponding to the maximum damage that attack could do. So an 1d6-2 attack on the flank would put a “4” token stacked with a “x2” token on the damaged unit, while an 1d6+2 attack from the front would inflict an “8” token, etc etc. The numbers on the token record the maximum amount of hits the unit could have received under RAW, so I call them ‘potential hits’.

Every time you acquire a new token, tally the total of potential hits so far. The above unit would have a total of (4x2)+8=16 potential hits on it. Only if and when the total potential hits reach or surpass 15, actually roll the dice corresponding to tokens. So in the example above, you would roll [(1d6-2)x2]+1d6+2. If those ‘actual’ rolled hits total 15 or more, the unit is destroyed. If you roll a lower number, the unit is still fine – but it still keeps all the tokens it acquired so far.

The effect of all this is that you won’t know exactly how close your units are to destruction when you activate them – you won’t have those 14-hits ‘dead unit walking’ situations in which you just want to squeeze one last suicidal attack from your little warriors. This also increases the fog-of-war in a sense, since you’ll never know how close to destruction the enemy’s units are – just the amount of pressure you’ve put on them. On the other hand, OHW’s RAW statistics and variance is fully preserved. In fact, the only difference is that you pack all the randomness in one big chunk when it actually matters, rather than parcelling it on a turn-by-turn basis and then being constantly updated with full information about an unit’s status.

It works for me!

Wednesday, January 27, 2021

‘Deterministic’ OHW Rules-As-Written (RAW) Playtest

My first round of OHW playtesting left me with a desire to amend specific aspects of OHW’s RAW. The last few posts were basically preliminary notes in preparation to do just that. However, I think there’s one more, necessary step before I commit to the changes I’ve written so far: more playtesting! I want to really cut down the changes down to the minimum to stay as close to the OHW spirit as possible. So, I want to be sure I fully understand – not the rules, which are extremely simple, but – their interplay and emerging features, which I think are the important part.

I will use Horse & Musket era rules since I think they’re the ones needing the fewest changes to provide tactically interesting and historically-flavored games. I will play several of the scenarios solo (damned pandemic). And I will play diceless, i.e. in a completely deterministic fashion. I’ll try to explain both how and why… but perhaps trying to be just a tad more humble than the Man Himself:


"Military science consists in first computing all the probabilities, and then, evaluate precisely, with a nearly mathematical method, what is the share of chance... Chance is a mystery for lowly minds, and it becomes a real thing for superior men." [Napoleon]

 ...ok, that sounded a bit snooty from you Bonnie, but modesty is not a typical curricular skill for Emperors after all.

How to play deterministic OHW

It’s very simple. I will use my hex mod (see this post) instead of free movement, and record the average expected hits of an attack (see this post) instead of rolling dice. For example, a standard infantry attack will inflict 3.50 hits on the target; a cavalry charge on the flank 11.00 hits. That’s it. Everything else will be as in the RAW.

OK, but… why?

I think there are two main styles of solo playing, and I usually refer to them as ‘playing to be challenged’ and ‘playing to learn’. The first one tries to recreate the same experience of a face-to-face game without an actual opponent, presenting a genuine tactical challenge via methods involving randomization, hidden information and/or programmed opponents. The second one is aimed at learning something new from the game, regardless of whether it’s ‘fair’ or ‘fun’ in the traditional sense; this basically just involves the solo player honestly pursuing the best interests of both sides at the same time. The latter approach is the one I actually prefer, and is described perfectly here and here.

My goals for OHW solo play are strictly in the ‘playing to learn’ camp, as I’d like to learn:

·         Implications of the rules: which tactics do they encourage? Are those historical or not? Which historical battlefield behavior is not represented?

·         Are the various unit types balanced? Is some type of unit generally less useful than others?

·         Is the scenario balanced?

·         What is the best Course Of Action for both sides in this scenario? How would a programmed opponent work?

In my view – and for the above goals only – randomization is just added noise. Randomization is surely fun in face to face battles or in ‘challenge’ solo games, where every die roll can dynamically change the situation. But when playing to learn, I think the best pieces of information you can come off with are the average/expected outcomes rather than the specific outcomes of a given randomization sequence. It’s like playing a large number of randomized games and averaging them, if you want. This does turn the game into a somewhat insipid chess-like version of itself, of course; but it serves the ‘learning’ goal very well.

Very basic example of randomless analysis: one-on-one engagement of line infantry units in the RAW

This is what would happen in deterministic OHW if a line infantry unit decided to attack another one (say it’s 15” away, above shooting range; red is the attacker).

One-on-one infantry engagement, average outcome per turn


Avg Hits on Red unit

Avg Hits on Blue unit

Red 1

(red moves into range…)

(…and cannot fire)

Blue 1

3.5 (blue shoots)


Red 2


3.5 (red shoots)

Blue 2






Blue 3



Red 4



Blue 4



Red 5



Blue 5



 This means that per the RAW, 1:1 infantry engagements are long, costly and risky.

Long: they need 5 turns on average to reach a decisive outcome.
Costly: the expected outcome is to leave the defending unit almost completely spent at the cost of one attacking unit. It’s almost like a piece exchange in chess.
Risky: they slightly favor the defender because it shoots first; but the advantage is small, making attacker victories possible.

[Side Note - it’s of course possible to compute just how risky it is for both opponents, when playing with dice… the results largely justify the ‘deterministic’ solo approach, in the sense that the distribution of outcomes as per the RAW won’t be that ‘dicey’ or ‘random’ after all. The real turning point seems to be Turn 4, in which you usually reach an equal chance of surviving or being destroyed. If you reach turn 4 in better shape than your opponent you should probably press forward… If not, there is no great dishonor in a quick tactical reassessment].

One-on-one infantry engagement, chance of elimination

Number of 1d6 attacks received

Per turn













49.52% (turning point!)










 All things considered however, the tactical lesson here seems to be “avoid 1:1 engagement at all costs if possible”. How does that sound, Nappy?

"The Art of War consists in the following: […] you concentrate more troops than your enemy on the point where you attack, or on the point where you are attacked. But this art cannot be learned in the books, or acquired as a habit; it is a way of acting which is the proper genius for war." [Napoleon]

…Well Bonnie, I can't possibly argue with someone in that attire. If you excuse my dumbness however - that’s more easily said than done, since I’ve found that this 'concentrating troops' thing is not that trivial after all. Guess it means I’m not a ‘proper genius for war’, huh?

The next few posts will be AARs of OHW scenarios played as above. Au revoir!