Collections: Logistics, How Did They Do It, Part III: On the Move

This is the third part of a three part (I, II, III) look at some of the practical concerns of managing pre-industrial logistics. In our last post, we outlined what ‘foraging’ actually entailed – how armies got supplies both from friendly populations but also from neutral or hostile populations. In particular, we focused on the considerable damage that armies could not fully avoid doing (not that many tried very hard) when moving over the countryside. Because of their limited ability to transport supplies, armies were forced to draw those supplies locally, to the considerable misery of the local rural population. For the average peasant, an army came upon them like a rolling calamity.

I want you to keep that misery in mind because we’re going to shift perspectives here to the perspective of the general in charge of campaign operations, but in the back of your mind you should also be thinking about what the calculations the general is making are going to mean for the underlying populace that will have to endure his decisions.1 This week we’re going to look at those decisions and how the interaction of foraging and marching shapes where an army can go, how fast it can get there and how large it can be. For the most part, because of the limits of space, that is going to mean simply covering the generalities of these concerns (with some models to walk through the interactions); this post is already terribly long and in any event getting much more specific than this is going to essentially require looking at the specific details of individual campaigns.

And before we march onward, if you want to support my logistics, you can do so via Patreon. If you want updates whenever a new post appears, you can click below for email updates or follow me on twitter (@BretDevereaux) for updates as to new posts as well as my occasional ancient history, foreign policy or military history musings.

A Good Road

The first concern for the general is to determine the route of march and the options here might be surprisingly limited. Just how limited, I suspect, often comes as a surprise to many modern students of pre-industrial campaigns; these days when we travel we have GPS route-finders that usually give several different possible paths, from highways to back roads. Even in the days before ubiquitous GPS, with a good road map, you could chart dozens if not hundreds of possible routes in a long distance journey. In many games, this freedom of movement is greatly amplified: marching armies, imagined to be no longer restricted to roads, are effectively able to march anywhere not bounded by obvious natural barriers (e.g. the more recent Total War titles, Mount & Blade, and Battle Brothers). Roads may supply a speed bonus (often a quite limited one), but are otherwise optional. Historical armies were far more limited.

Screenshot from Mount & Blade: Bannerlord. The developers have actually added a lot more roads over the past few updats but there are still villages (lower right) completely unconnected by any kind of road or path. There is a speed bonus on the roads but it is small enough that armies regularly cut across country as you can see here.

Armies almost generally had to move over longer distances via roads, for both logistical and pathfinding reasons. For logistics, while unencumbered humans can easily clamber over fences or small ridges or weave through forests, humans carrying heavy loads struggle to do this and pack animals absolutely cannot. Dense forests (especially old growth forests) are formidable obstacles for pack and draft animals, with a real risk of animals injuring themselves with unlucky footfalls. After all the donkey was originally a desert/savannah creature and horses evolved on the Eurasian Steppe; dense forest is a difficult, foreign terrain. But the rural terrain that would dominate most flat, arable land was little better: fields are often split by fences or hedgerows which need to be laboriously cleared (essentially making a path) to allow the work animals through. Adding wagons limits this further; pack mules can make use of narrow paths through forests or hills, but wagons pulled by draft animals require proper roads wide enough to accommodate them, flag enough that the heavy wagon doesn’t slide back and with a surface that will be at least somewhat kind on the wheels. That in turn in many cases restricts armies to significant roadways, ruling out things like farmer’s paths between fields or small informal roads between villages, though smaller screening, scouting or foraging forces could take these side roads.

Via Wikipedia, a detail of the Tabula Peutingeriana or the Peutinger Table, a 13th century copy of a map of the Roman road system of an uncertain date, probably fourth or fifth century. This wasn’t a military map or indeed even necessarily a practical map (it has been suggested that it might have been a display piece), but it gives a sense of the complexity of the Roman road system, constructed initially and principally to enable the rapid movement of Roman troops around the empire. It also gives a good sense of the limited ‘spider’s web’ of good roads between major settlements.

(As an aside: one my enduring frustrations is the tendency of pre-modern strategy games to represent most flat areas as ‘plains’ of grassland often with a separate ‘farmland’ terrain type used only in areas of very dense settlement. But around most of the Mediterranean, most of the flat, cleared land at lower elevations would have been farmland (something you can see fairly clearly in the city maps I’ve included here), with all of the obstructions and complications that implies; rolling grasslands tend to be just that – uplands too hilly for farming.)

The other problem is pathfinding and geolocation. Figuring out where you off-road overland with just a (highly detailed) map and a compass is sufficiently difficult that it is a sport (Orienteering). Prior to 1300, armies in the broader Mediterranean world were likely to lack both; the compass (invented in China) arrives in the Mediterranean in the 1300s and detailed topographical maps of the sort that hikers today might rely on remained rare deep into the modern period, especially maps of large areas. Consequently it could be tricky to determine an army’s exact heading (sun position could give something approximate, of course) or position. Getting lost in unfamiliar territory was thus a very real hazard. Indeed, getting lost in familiar territory was a real hazard: Suetonius records that Julius Caesar, having encamped not far from the Rubicon got lost trying to find it, spent a whole night wandering trying to locate it (his goal being to make the politically decisive crossing with just a few close supporters in secrecy first before his army crossed). In the end he had to find a local guide to work his way back to it in the morning (Suet. Caes. 31.2). So to be clear: famed military genius Julius Caesar got lost trying to find a 50 mile long river only about 150 miles away from Rome when he tried to cut cross-country instead of over the roads.

Detail from map 7.2, “Campaigns of Caesar, Crassus and Pompey” from The Romans: From Village to Empire created by the Ancient World Mapping Center. You can see the Rubicon River (quite small) clearly labeled as well as its relative distance both from Rome (where Julius Caesar was from) and Cisalpine and Transalpine Gaul (where he had been the Roman proconsul for nearly a decade).

Instead, armies relied on locals guides (be they friendly, bought or coerced) to help them find their way or figure out where they were on whatever maps they could get together. Locals in turn tend to navigate by landmarks and so are likely to guide the army along the paths and roads they themselves use to travel around the region. Which is all as well because the army needs to use the roads anyway and no one wants to get lost. The road and path network thus becomes a vital navigational aid: roads and paths both lead to settlements full of potential guides (to the next settlement) and because roads tend to connect large settlements and large settlements tend to be the objectives of military campaigns, the road system ‘points the way.’ Consequently, armies rarely strayed off of the road network and were in most cases effectively confined to it. Small parties might be sent out off of the road network from the main body, but the main body was ‘stuck’ on the roads.

That means the general does not have to cope with an infinitely wide range of maneuver possibilities but a spiderweb of possible pathways. Small, ‘flying columns’ without heavy baggage could use minor roads and pathways, but the main body of the army was likely to be confined to well-traveled routes connecting large settlements. But which routes to take? That leads to the next concern…

Carrying Capacity

The general now has to pick the route where the key question is supply (particularly food supply) as we discussed earlier. Because of the ‘tyranny of the wagon equation,’ there needs to be sufficient food and fodder supplies along the army’s route to sustain it as it moves and accomplishes its objectives. Determining what routes are viable is thus a complex calculation (some of the variables of which will only be known to approximation), dependent on how fast the army will move, the local population density, the efficiency with which the army can forage or demand supplies from that population, the time of year, the army’s capacity to carry those supplies, how long the army needs to spend doing actual combat operations (like sieges) at the end of the march and most importantly how large the army is (and thus its need for supplies). Because the army can carry some supplies (frequently around two weeks) these variables mostly function as questions of the ‘rolling average’ which, if they fall below a certain level, will put the army into severe difficulties.

Let’s take our sample Roman consular army as a starting point: a relatively lean army with 19,200 combat effectives, 4,000 non-combatants and 9,800 animals which thus needs 61,850kg of food and hard fodder daily. Such an army might be able to forage 10% of the available food along their direction of march while still moving at speed; for now we’ll say the speed of march is 12 miles per day (we’ll come back to this in a moment, but that pace is not insanely fast but fairly brisk). With a fairly chunky cavalry detachment (2,400 cavalry) the army can probably forage out ten miles in either direction of its zone of march, so it sweeps an area close to 240 square miles per day. If we’re marching right around the harvest we might assume that each person in the countryside has something like 250kg of wheat or equivalent food, including fodder.2 Thus getting the daily 61,850kg required means each day’s 240 mile foraging zone needs to contain at least 618,500kg of grain or a population of at least around 10 per square mile.

Is that good? To get a sense of that we have to get a sense of what kinds of population density were normal in pre-industrial and pre-modern societies in the broader Mediterranean. Luuk de Ligt3 accepts population densities for Roman Italy overall between 70 and 95 people per square mile (his figures are in square kilometers so I am converting to keep consistency), but with tremendous variation inside of that, with dense regions like the ager Romanus and Campania around 110 people per square mile but places like Etruria and Umbria as low as 20. Italy, however, was one of the densest populated areas in Europe in the ancient and medieval periods (the other being the medieval Low Countries); rural population densities in Europe more broadly over large areas will have tended to range from 25 to 50 people per square mile, falling below that in rough upcountry regions (e.g. the population density of Scotland in the medieval period may have hovered between 10 and 15 people per square mile).

So right after the harvest our army of 19,200 effectives can go almost anywhere there is a road or good path and rural settlement. Great! Except of course the amount of food and fodder in the countryside isn’t static. Hay and oats – key sources of fodder for our animals – ripen and are harvested beginning in May, wheat comes in in June or July and barley in between the two. Consequently the available supplies (food and fodder) peak in those months and immediately begin falling. By October perhaps a quarter to a third of that supply is gone (plus by this point carefully stored seed grain is going back into the ground!); suddenly we’re looking at something like only 175kg of food supplies per person in the countryside, which means our army needs a population density of around 15 per square mile. Worse yet, if we plan to winter in the field (that is, we’re not dismissing the army home), we have to think about stockpiling for the conditions in January and February when forage becomes very scarce indeed. Realistically to do that, even with our fairly compact army, we need a population density of 20-25 people per square mile in order to build up winter stockpiles to last through the lean months. At these levels, low density areas with lots of pastoralism and not a lot of towns are effectively off-limits: the army would have to fall back to denser farmland for the winter. And indeed, we see this exact behavior in many ancient armies that stayed in the fields year round that had to fight in less densely settled regions – they campaign in the restless uplands and forests but always with an eye towards dropping back to winter quarters in densely settled river valleys or coasts.

But we’ve made some fairly favorable assumptions about our army: it is fairly fast and fairly compact. We’ll deal with the impact of speed in a moment, but what if our army is bigger? Well, this is initially fairly simple if we assume a constant movement speed: double the size of the army and that doubles the food and fodder requirements which requires double the population density. So a double consular army of 38,400 effectives (plus 8,000 non-combatants and 19,600 animals) requires 123,700kg of food and fodder and thus a post-harvest population density of 20 per square mile over the campaign area, rising to around 40 if the army doesn’t want to have to disperse in the fall. That army suddenly has some fairly severe limits on where it can go outside of the couple of months right after the harvest; routes that run through less densely peopled territory are no longer options for that army.

But what if, instead of doubling the size of our fairly compact army, we assume an army whose non-combatant load looks something more like the Army of Flanders, where the non-combatants of the campaign community might number around half as many as the combatants (and in some cases equal their numbers). Suddenly our 19,200 effectives army now has roughly 30,000 mouths to feed; managing the baggage of the non-combatants probably adds a few animals too, perhaps bringing us up modestly to 12,000 or so. Now we need 77,500kg of food and fodder and thus summer population density of 13 people per square mile and a year round density of 26. Doubling the size of this army doubles those figures, requiring a harvest density of 26 and a year round density of 52 – such an army would either be limited to campaigning in only densely populated corridors or it would have to march divided to sweep a larger area of foraging. As hard as it is to exclude non-combatants from an army, they inflict much the same logistical load as combatants, limiting the operational capabilities of the army to which they are attached.

But that treats the size of our army and the speed of its march as independent variables. Unfortunately for our army, they are not independent variables, rather (with many other factors considered) big armies move slower. The problem is…

Road Space

We’ve dealt with this problem before from other angles, but armies do not move as a theoretical ‘point mass’ like in a physics problem (or how they are represented in many video games), rather their elements take up road space, one after the other. An army on the march is thus not a battle line or a compact mass but a long, snaking series of columns. That in turn has substantial impacts on its rate of movement, because the front of the army has to march past the back at the beginning of the march and the reverse has to happen at the end.

Photo by R.B. Ulrich, detail of scenes 4 and 5 showing Roman soldiers marching with their gear (carried in their packs you can see above them on sticks) over a set of pontoon bridges over the Danube River, from Trajan’s Column. Armies, being very big, take up a LOT of space.

So how much space might an army on the march take up? I’m going to be drawing some numbers here from J.A. Moss, Manual of Military Training (1914), because I happen to have a (well used) copy of the 1917 edition. It calls for a rank distance (the distance between the back of the man in front and the chest of the man behind him) of 40 inches, which is fairly standard; adding in the width of the soldier themselves and their pack each rank takes up around 1.25m (c. 4-5 feet) of road space. Formed six soldiers wide (which will, with minimal intervals, get us to the width of most single-carriage roadways, which what we are likely to be dealing with), our model army’s infantry component (16,800) would have 2,800 ranks to it moving in column.

But we can’t just march the army in one single mass like that. Intervals between units are necessary for control (so that officers can keep an eye on their whole units and ensure soldiers aren’t wandering off, straggling, injured, sick, etc.) and also to avoid ‘accordioning’ into each other as units ‘tailed out.’ Moss (1917) assumes intervals but does not specify them; Lockwood, Organization and Tactics (1895) offers the rule of thumb of allowing an extra 10% road space for a battalion, 15% for a division and 20% for an army corps. So instead of one infantry body of 16,800 men, we can divide it into 35 cohort-sized ‘battalions’ of 480 men each. Each of these battalions thus has 80 ranks taking up 100m of road space, plus an extra 10m for a unit interval to the next unit. Our infantry thus take up 3,850m or 2.4 miles of road space.

Cavalry takes up more space because horses are big. Lockwood offers that each individual horse takes up a depth of 3 yards and a front of around 1 yard (compared to 28 inches for an infantryman), so the cavalry might ride in column four abreast instead of six. Once again we also need unit divisions; for the sake of simplicity we’ll use a rough ‘squadron’ of 100 cavalry (a touch bigger than a typical cavalry squadron but there is a lot of variation here too: the Romans divided their cavalry into turmae of 30 each, which were quite small units), which is going to form 25 ranks of four cavalry each requiring 2.75m of road length (about three yards), so 68.75m plus our interval (10%) makes roughly 75m per squadron. With 24 of these squadrons to make our 2,400 cavalry they take up some 1,800m of road space, or 1.1 miles.

Via the British Museum, a drawing (1625-1664) of an army marching out of a fortress, stretching out along the road out of sight in both directions.

And then we need the baggage, which here is being moved by 5,000 mules and 2,400 spare horses. The mules will be a bit more compact than the horses per animal, but we’re still probably looking at something like 2.25m per mule (and 2.75m per horse) set four abreast on the road. That’s 1,250 ranks of mules (2,812.5m) and 600 ranks of horses (1,650m) for a total of 4,462.5m taken up by the baggage train. In practice while a some of that will be in a large mass in the center of the army (see below), a lot of these animals are going to be split up into small groups at the tail of their units (each infantry ‘battalion’ should have 80 mules – 45m of them – at its tail). With so many possible configurations, it seems tricky to try to calculate open intervals for the baggage train; perhaps (in small bits spread over the army) they might add something like 440m minimum, so their total road length is just short of 5,000m (3.1 miles). As for the non-combatants, our army is quite lean and many of those non-combatants are in practice guiding the mules and the horses; we can include them here for now.

So that’s our army, a snake-like beast 6.6 miles (10,650m) long, winding through the landscape. Now we can think about…

Marching Speed

Unladen human walking speed on flat terrain with long strides is just over 3mph; it will not surprise you to learn that for a large army marching more precision is required. Going back to Moss (1917), he assumes the length of step of the average man is 30 inches (in practice, keeping up with standard march rates and thus standardizing gait is something soldiers will learn by training and experience) and one of the chief jobs of a commander on the march is determining the correct ‘rate of march’ – Moss even recommends the unit commander (at the front since the front unit sets the pace for everyone behind) time the pace every so often to maintain a steady marching pace. The standard paces for marching under loads are between 88 and 110 steps per minute, which come out to 2.5 to 3mph.

The army does not, however, move continuously at this speed. Moss (1917) sets out the guidelines for rest: a 15 minute half after the first three-quarters of an hour (with an effort to do this away from settlements), followed by a 10 minute halt every 50 minutes (adjusted to 45 minutes march and 15 minute halt in tropical or arid climates). In very hot environments, Moss (1917) notes you ought to also halt for three or four hours during the heat of the day (so around 1-3pm in most cases), but we’ll assume we’re not marching in that hot of a climate. But that means our formation, humming along at 3mph is actually only moving every 5 minutes out of 6 or 3 minutes out of 4; that means our actual average speed is 2.25-2.5mph, even though when moving we achieve a 3mph march.

Via the British Museum, a print (1650-1695) by Gabriel Perelle showing officers (on horseback) looking over soldiers (both infantry and cavalry) marching past fortifications. Note the wide intervals between units.

But we also do not move for eight straight hours at this speed seven days a week. Marching soldiers under load straight through the whole day will, understandably, exhaust them; this may be necessary in some cases (where it is called a ‘forced’ march), but it is rarely desirable. After all, the army is supposed to fight at the end of this and has to reach that destination ready for the exertion of battle or siege. Moss (1917) recommends that “as a rule, foot troops do not start before broad day-light; mounted troops, when practicable, about an hour after broad daylight” (1219), in part to avoid losing the valuable rest of the early morning hours and in part because trying to move before the sun is fully up and visibility is best is silly. Now that’s obviously a time that is going to vary a fair bit by latitude and time of year, with anywhere from 10-15 hours of proper daylight to work with.

So let’s say we are on the Mediterranean coast of Europe (I’m picking Marseilles for my times here) in early May. The ‘false dawn‘ is going to start around 4:30 and we’ll have enough light to actually do things by around 5:30 or so; remember options for artificial light here are very limited (laterns and campfires; torches4 are more common in fiction than actual use) so we need actual sunlight to do much of anything. And there are things to do! Soldiers need to wake up, eat breakfast, handle personal hygiene and dress, break down their tents and the camp and fill canteens (the necessity of filling canteens with water in the morning is something I have seen in every infantry marching manual I have ever looked at for obvious reasons), all of which takes time. In the United States army, ‘reveille’ – when soldiers can be expected to actually fall in with units – is set at either 6 or 7 am and its easy to see how this fits as that’s almost precisely the ‘broad daylight’ of marching, while using the dawn hours to get ready. Cavalry needs an extra hour because, of course, the horses.

Via the British Museum a print (1535-6) by Erhard Schon showing several armies marching out of their camps in columns to besiege the city of Münster.

So it’s 7am and we start marching! Well, not quite. Someone starts marching. But the back of the army now has to wait for the entire rest of the army to march past it in sequence. That’s going to take time! Recall our army is 6.6 miles long and moves at 2.5mph; it’s going to take a bit more than two and a half hours before the last elements of the army begin leaving the camp in ideal conditions (this factor shows up a bit less in 1800s manuals because by then it was very common for armies to march divided; this was very rare for earlier armies). So it will probably be almost 10am before the entire army is moving. But now we have our problem in reverse form: the front of the army must stop and set the camp somewhere the back of the army can reach before the sun goes down. Night marches, as Moss (1917) is noting even in the 1900s, are difficult and perilous. So while the sun starts to set around 8:30 or so, we’re going to lose that two and a half hours again on the back end; the front of the army must stop marching around 6pm at least so the rear of the army has time to catch up before sunset.

In practice it is yet worse than this because of course we need to set up the camp again at the other end of the march, which is also going to eat precious time. And while the day gets longer in the summer, soldiers do not magically become supermen of endless endurance in the summer (if anything, as the heat rises, the reverse is true: marches must become shorter) meaning that they need time not merely to set up camp, but also rest, cook food, attend again to hygiene, the maintenance of weapons and equipment and so on. You can get more marching hours out of the day but only by eating up those rest hours which the army needs to be combat fit. This is why, as Moss (1917) notes, “forced marches seriously impair the fighting power of even the best troops” (1225).

So we have perhaps a standard marching day: the army wakes around 5:30-6am. The front is formed up at 7am and properly starts moving (after scouts and screens head out) at 7:30 or 8am, the back starts marching at 10am in the best case; the army halts around noon to eat (long marches on empty stomachs are a recipe for fatigue casualties; I cannot stress enough that while physical fitness and training obviously matter in all of this, heat, dehydration, hunger and exhaustion do not care how many reps you can do and the general has to get his whole army to the battlefield ready to fight). The back of the army probably needs to be making camp by 5:30pm or so (to have time to setup the camp – especially if it is a fortified camp – before nightfall), so that means the front of the army has to stop around 3pm.

So while some part of the army is probably moving at every point between 7:30am and 5:30pm, the actual effective marching time – initially 10 hours minus one for lunch – is reduced by 2.5 to just 6 or 7 hours if absolutely everything went right. At c. 2.5mph average, our army would make 15-17.5 miles in a day. But of course everything isn’t always going to go right; if it’s hot (in summer, recall) our speed drops to 2.25mph and our distance in a day to 13.5 to 15.75 miles. If the roads are bad, we lose yet more time, especially if the roads narrow at any point, forcing the army to stretch out even more. I want to stress we are still mostly working with best-case situations, but we’re already looking at figures right around the 12-15 miles per day that most rules of thumb consider the upper end of long-term sustainable marching base for infantry moving along good roads.

Now let’s fiddle with our assumptions a bit. What if the army carries a lot more baggage? This could be because the army needs to carry more supplies to get past areas where forage options are limited (either by low population or by the presence of enemy forces) or because the army is having to move a large siege train. If we, for instance, remove our mules (so save 2,812.5m of road space, but lose c. 650,000kg of carry capacity) and replace them with 700 heavy wagons (c. 1,000kg carrying capacity per), we can expand our logistics (because we’ve dropped from 5,000 mules to perhaps 2,800 horses and likewise the number of required non-combatants to handle the mules has gone from 3,400 to just 700 wagoneers) and have some space for a heavy siege train. At best we might cram each wagon into something like 12m of road space (American Civil War rules of thumb was 80 wagons to a mile, or each wagon taking up 66 feet or 20.1m), so our new wagon train is now 8,400m long. That’s 5.2 miles of baggage alone, so now our army is a stunning 16,237.5m long (10 miles). In very good roads we might double up the wagons and get down to just 12,037.5m or (7.5 miles).

Which in turn means our ‘lost marching time’ extends from just 2.5 hours to 3-4 hours (be careful not to double-count the loss, subtract either from the front or the back to get the correct number of marching hours, not both), leaving each unit with just 5-6 hours of actual marching, reducing our daily rate of march to between 11.125 and 15 miles per day, under ideal conditions if everything goes right and not one of those seven hundred wagons breaks down (of course the same was true of having not one of 5,000 mules become injured or stubborn as mules are wont).

Likewise, if we take our original army and double its size, either by adding more combatants or by loading it up with more non-combatants (now so numerous that they are not all simply handling the mules but are filling up even more space in the line), that doubles its road length demand out to 13.2 miles. That means our ‘lost marching time’ is suddenly 5-6 hours leaving just 3-4 hours of total effective marching time. Suddenly our army is crawling at between 6.75 and 10 miles per day – under best case conditions! – even though our ‘start’ and ‘stop’ times have not changed at all.

In practice we’re actually still being a bit too nice to our army: we’re assuming they march every day. But while humans can more or less do that, pack and draft animals cannot. In practice for a sustained march these animals need to be rested one day out of six or so or the strain will render them useless in the long term. So our lean, compact army is really moving around 12.5-14.5 miles per day over a six-day average with one day of rest under normal conditions (a bit faster if they push it, a bit slower if they don’t) and our double-sized army could be moving as slow as 5.6-8.3 miles per day.

The key observation here is that everything you add to the army slows it down. A good general has some options to mitigate this (but they all come with risk), but the fundamental rule remains. Adding more baggage to carry artillery or supplies slows the army down. Adding more soldiers to try to improve your chances of victory slows the army down. Adding more non-combatants to the ‘campaign community’ slows the army down, though remember from the earlier two posts, depending on the organization of the army and the expectations of the soldiers, some significant number of non-combatants may be effectively unavoidable.

Sink or Swim

And now that we have our range we can return to some of our independent variables and see how they collide. Recall that during the summer our compact, mid-sized 19,200 soldier army could go anywhere where the population density was at least 10 or so people per square miles.

Now let’s see what happens when we double the size of that army. First, it’s food needs, as we’ve noted, double from 61,850kg to 123,700kg of food and fodder, so the number of people it needs to forage in a day (at a 10% forage rate) goes up from 2,474 to 4,984. And you are thinking, “Yes, we’ve done this math and we know this ends up with them needing around 20-25 people per square mile after the harvest.” Ah, but our forage area has also changed.

Because our army isn’t clipping along at 12 miles per day anymore, it’s slowed down to an average of perhaps 7 miles per day. That in turn means our foraging zone isn’t 20 miles by 12 miles, but 20 miles by 7 miles: we’ve gone from 240 square miles of forage to just 140. So our required population density has actually leap from just over 10 to 35.6 people per square mile, more than three times as high because the increased nutrition demand and decreased speed have compounded. And that is, you will recall, the situation immediately following the harvest. By October that figure is going to have risen to something like 46 people per square mile; the year-round campaigning requirement would be close to 70 people per square mile.

Those aren’t impossible numbers, but they are going to pose the general of this army with some difficult choices. What will not work is overland external supply with more wagons; as discussed the animals eat food and so adding more wagons just slows the army down more and increases its food demands; that’s the tyranny of the wagon equation at work – the army cannot wagon its way out of a foraging pit. One option is to forage more intensively to raise the percentage of food in the countryside the army is pulling in; this poses twin problems. The first is that doing so generally means either slowing down or dispersing foraging parties for more effective searches; the former may be counter-productive, the latter may be dangerous. In either case, foraging beyond 10% is likely to cause fairly immediate and sharp starvation in the countryside; pushing that number higher is going to risk invoking Marshal Villars’ warning from last time, “If you burn, if you drive out the population, you will starve.” Not today, but tomorrow; if the army has to return home through this same route or intends to operate in this area again soon, depopulating it by over-foraging merely delays disaster. Nevertheless, faced with the exigencies of war, many armies did just this, ruining the local population to enable the movement of oversized armies.

Another option is to speed up, thus increasing the foraging area. The march could be lengthened, but that is going to have negative impacts not merely on morale but on combat readiness: after days of regular long marches under heavy loads soldiers will begin to suffer from exhaustion. Instead many generals opt to trim the baggage, trying to get rid of every sort of excess thing; this is common enough that it becomes a sign of good generalship in the ancient world – the good general enforces discipline, compels his soldiers to get rid of everything they carry that isn’t strictly necessary, maintains morale by doing the same himself and then for good measure kicks every unnecessary non-combatant out of the camp. Unfortunately for our general, we’ve already started with a very lean army, by pre-industrial standards, so there isn’t very much fat to trim (which is partly why most actual armies, which were not so lean, marched at speeds that tend to cluster at the bottom of these ranges we’re creating; the other big reason why is we’re assuming pretty good road conditions which will not have pertained generally). However a general can also push an army by lengthening the marching day and raising the pace; doing this for long periods will wear out an army quickly, but for quick, short-term solutions to supply problems (or for rapid operational maneuvering) there is a fair bit of flexibility in daily marching rate. Morale ends up as a major consideration here: motivated soldiers (either inspired by their general or their cause) may push harder on the march, allowing the army to sustain a higher rate of movement, sticking closer to the 10 or 12 miles per day and thus alleviating some of the supply issues.

A third, more complex option is to march divided, splitting up the army to move in several separate columns along different roads which can both move faster (because they are now two smaller armies) and can forage different farmers in different areas. The problem this poses is simple: coordination. An equal sized enemy who remains concentrated could engage one of those armies, win easily due to the 2-to-1 numbers advantage, then turn and obliterate the second army, what is known as ‘defeat in detail.’ To avoid that the general in overall command has to coordinate so that these armies march separately but arrive at the battlefield at the same time. This sounds easier than it is: the general may not know where the battle will be (because he does not know where the enemy army is) and he has to plan (at least) two routes of march which will get both armies to the critical space with a margin for error measured in hours at the end of a march which may be days or weeks (or months!) long. This can be done, but it is very difficult and very easy to completely ruin a campaign with a fairly minor mistake; in practice before 1800 or so, most armies only operated like this if they absolutely had to.5 In practice the threshold where armies end up forced to split up is somewhere above 50,000 effectives, depending on conditions.

Finally there is a fourth option available in only certain circumstances: naval (or river) supply. This is, all things considered, somewhat rare; most ancient and medieval polities were not up to the task of supplying large armies by sea regularly at long distance (though the Achaemenids, Athens, Carthage and Rome all do this at one point or other and if you are thinking, “gee, those seem like some of the highest state-capacity polities in the ancient world” why yes, yes they do.).6 Nevertheless ships and river barges offer an escape from the tyranny of the wagon equation: the food consumption of the crew is effectively trivial compared to the amount that they can move. The result is that an army at a decent port with access to the sea (directly or by navigable river) has access to effectively infinite supply throughput, assuming that the supplies can be assembled and safely shipped. The problem that most pre-modern polities would struggle to do that is a separate issue, but a significant one. One of these days we may come back and talk about Roman naval and riverine supply in more detail.

Underlying all of this is a central fact about armies before railroads: armies are like sharks, they must swim or they will sink.

Now Add Hostile Armies

Now so far we’ve been considering our army moving through a countryside devoid of actual resistance, but of course the enemy gets a vote! Foraging in enemy territory is a dangerous activity; troops that are searching farmhouses or hauling large amounts of supplies (or pillage) aren’t going to be in fighting trim. In many cases they may not even have their weapons and armor (e.g. Liv. 31.2.8; Caes. BG 4.32.5), since working light means being able to shift larger amounts of forage and pillage. Moreover as we’ve discussed getting an army into fighting formation quickly is hard; if your unit is foraging in a village and an enemy unit suddenly attacks, the chances of effectively defense are very low indeed. That’s why foraging parties had to be so large, so that some of the foragers could be on guard while others were doing the actual foraging. The Roman historian Livy has an interesting description of command failures leading to an ambushed foraging party, noting that the commander, Gaius Ampius, had failed both to sufficiently scout the area but also setting up sufficient strong-points from whence armed soldiers could protect and screen the unarmed ones (Liv. 31.2.8).

Of course those sort of arrangements are only going to work against small parties of enemies (like their own foragers and scouts); against the main force of an enemy army those scouts and guards really function just to give the army enough time to retreat and concentrate for a battle. Because of that ‘defeat in detail’ threat, if the enemy’s main field army is nearby and close enough in strength to offer battle, it becomes necessary to keep your own army concentrated; even if you don’t intend to offer battle as situations like that at Pydna show, battle may happen regardless. But of course as we discussed back then, generals here have at best limited and often badly out of date information about the composition of location of enemy forces; a general thus has to balance his need to move and feed his army with the knowledge that the enemy could show up at almost any time.

That starts, of course, with marching formations. We’ve described how it takes time for an army to get moving in the morning, but there’s an additional complication to this: the order of march isn’t itself random. Exact formations vary but there was a fairly standard setup: proceeding the army was often a screening force of scouts (often cavalry), followed by the vanguard (or ‘van’), a combat unit or several marching some distance in advance of the main force, often with minimal baggage. The general himself often moved with the vanguard because that’s where information would be quickest come by. Then came the main body of the army, typically with the baggage train in the middle sandwiched between combat elements (which typically composed the bulk of the army’s infantry). Those combat units might also (as above) have their own smaller baggage trains directly behind them in the marching order or it might all be centralized in the center of the army (the latter was the Roman practice). Finally there was a rearguard, more or less a mirror of the vanguard. That layout ensured the army could respond relatively rapidly to the sudden appearance of an enemy in front or behind. For extra security, light infantry skirmishers with minimal baggage might also be detached as ‘flankers’ moving off the road or along side roads so that the army couldn’t be surprised from those directions either.

Typical advice (this actually comes up in Moss (1917)) is that a commander needs to both rotate which units are in the vanguard and rearguard and that his subordinates need to rotate which part of their command is at the front and back of their units, regulating the pace. There are many silly things in the film Gettysburg (1993), but one moment I just love is Chamberlain’s exasperation on realizing on top of an already difficult morning that his regiment has been assigned to the front of the front brigade in the corps and so has to assign flankers; that rotation would have been regular in most armies. And what would have happened to create this scene, is that the commander of the V Corps (Major General George Sykes) opted to march with his first division in the front, which then its commander (Brigadier General James Barnes) opted to put the 3rd Brigade in front and its commander (Col. Strong Vincent) opted to put the 20th Maine in front and of course its commander (our Professor of Rhetoric, Joshua L. Chamberlain) would in turn have to pick where each of his companies would go. The main concerns for smaller units is that the front part of the unit regulates pace and the rear part of the unit will need to deal with stragglers (including heat and fatigue casualties) as well as keep up pace to avoid the unit ‘tailing out’ too badly as it marches.

Also absolutely fantastic shot composition where we can see the oak-paneled wooden acting of the courier who sounds like he is reading his lines from an index card, but where we can’t see the faces of the characters we actually care about and what they think about this information. Gettysburg (1993) is a film that fills me with conflicting emotions is what I am saying here and that’s before we get to all of the Lost Cause rubbish they inexplicably put in between the scenes involving Buford and Chamberlain.

Foraging opportunities would also be shaped by the enemy presence and this could be a crucial operational concern. Because foraging operations were so vulnerable the presence of a large enemy force could prevent them even if it didn’t give battle. This is often what is happening when one commander ‘bottles up’ another without ever giving battle – by simply saying close to but out of reach of an enemy army, the weaker or more timid force can massively complicate their logistics. Roman efforts against Hannibal in southern Italy after Cannae (so from 215-203) as a master-piece of this kind of maneuvering. The Romans after Cannae had accepted that further direct engagements against Hannibal were unwise, but on familiar ground and close to their own bases of supply, Roman armies could operate freely where Hannibal needed to forage to advance. By simply staying close to him Roman armies could restrict his ability to forage and thus his ability to maneuver at all, forcing him to remain close to his base of support in southern Italy.7 Of course such a strategy only prolongs the conflict, but the Romans had other armies that were chipping away at every other corner of Carthage’s empire.8

Armies in close proximity might still manage to forage by sending out very large foraging parties (e.g. App. Pun. 100, Caes. BAfr. 68; Bohemund’s large foraging party that engages Duquq of Damascus during the Siege of Antioch (1097-8) also seems to be an example) or by pointedly sending their foraging parties away from the enemy force (as with Antony and Octavian’s foraging efforts between the two engagements at Philippi in 42, App. BCiv. 4.122; given the size of the armies this must have been a desperation move to extend their operational endurance; they could not have been permanently supplied on that basis). Still at best the presence of an enemy army might cut the available foraging territory of an army on the march in half, which for armies of even a fairly modest size is going to push the required population above sustainable levels quickly. Of course that is happening to both armies, which is part of why ancient and medieval generals are so confident they can force their enemies to battle once the armies get close: both armies, unable to forage effectively, have ticking clocks in most cases. Exceptions do happen (especially when one army has naval supply), but for the most part the supply situation will eventually compel each army to either fight or retreat.

Absent a full field army, a fortified site (like a castle) with a strong cavalry detachment could achieve similar operational results in restricting enemy forage opportunities. Indeed, as we’ve discussed, this is how castles worked at the operational level: the presence of troops (specifically mounted troops) in the castle made effective foraging or administration of the land around it impossible for any invading force that didn’t also lay siege to the castle. Consequently an army looking to maneuver in the region had to neutralize the castle first or else swiftly march past it into less well-defended farmlands that could be foraged effectively. Fortified cities and hill-top towns (oppida) posed similar problems for Alexander the Great and Caesar respectively: if captured or made friendly (either by alliance or preemptive surrender) they were sources of supply, but such a settlement untaken could create supply deadzones and serious risks in the rear of the army. Indeed the emperor Julian gets himself into precisely this problem with an audacious march into Persia without fully securing the rear (Ctesiphon being too well defended), ending up in a situation where the army could neither safely advance nor retreat. Consequently even when the road was open there was often no alternative but to besiege and take these strong points.

Managing Operations

All of which at last lines up most of the most pressing concerns a commanding general has when considering the march of an army. Of course the general does not have some of this information to the precision we’ve modeled it here: he does not know the exact population density of the regions he is going to march through and instead is probably thinking in analog terms: some areas are ‘rich’ some are ‘sparsely peopled’ and so on (which is to say a wise general is going to want a pretty big ‘margin of error’ on those daily foraging calculations); likewise the expected rate of march over a long period must on some level be an informed guess rather than an exact calculation.

Still, the general has to first select an objective (probably the capture of a major civilian center which will bring with it the countryside it administers), then figure a route of march to get there. He probably has a decent sense of how much food and fodder his army will need but at best an imperfect sense of what is going to be available in enemy territory or where enemy armies might be; that will demand improvisation on the march in response to changes in the army’s food supply. The army’s rate of movement is variable, but while pushing hard can solve logistics problems, it can also exhaust soldiers, deplete morale or involve leaving heavy (but important) baggage behind; marching fast to defeat in battle is a mistake many commanders make (e.g. Marcus Antonius (‘Antony’) at Mutina in 43, Crassus at Carrhae in 53, Antony against Parthia in 36, Harold Godwinson at Hastings in 1066, Antony at Actium in 31. Antony does this a lot. I confess I have never quite understood his reputation among some historians as a ‘great captain.’).

Indeed it isn’t uncommon to see skilled generals employing a variety of solutions in response to conditions at various points in a campaign. Once again, the reader who wants a vivid example would do well to simply read Caesar’s Commentarii de Bello Gallico. Caesar makes a dynamic mix of solutions to supply and movement difficulties, especially since the terrain of Gaul largely cut Caesar off from Mediterranean sources of supply beyond the very beginning of his campaigns. Caesar often divides his army to accomplish multiple objectives or to move quickly (although this comes very close to disaster, e.g. Caes. BG 6.32-42 where Caesar splits his army up and very nearly loses his camp as a result) and as noted always seems to be arriving at rich farm country or prepared stockpiles of supplies just as his own is running out (which in turn is allowing him to move light with minimal baggage and thus move fast, Caes. BG 1.23, 1.34, 1.48, etc). Honestly a good, up-to-date logistics-and-campaign history of Caesar in Gaul really is desideratum.9 At the same time, Caesar’s motivational ability clearly also plays a role: both his ability to get his soldiers to both maintain discipline and push themselves on campaign but also his ability to retain their confidence even during marches where food supplies might seem dangerously low (though it’s not clear if he let them know that; Caesar showed special attention to the days set for regular grain ration distribution possibly for this reason – knowing that missing a day might not cause instant starvation but would cause his soldiers to lose certainty in his leadership).

On the other hand, of course, in a contest against another other thinking humans, victory often depends on riding the line of failure as tightly as possible without going over; Caesar repeatedly comes within sight of logistics disaster when making rapid movements – his famed celeritas (‘speed’) – but always lands on sufficient supplies at the last minute. As you might imagine from how the baggage train slows an army down, a ‘flying column’ with just a few days food can move very quickly, but of course must achieve its objective quickly and return. Once again the element of calculated risk here is very high; when Alexander learned that Darius had been seized by Bessus (330BC) he launches himself in that direction with a flying column with just two days supplies (hoping to capture Darius, Arr. Anab. 3.21.6-10; on this see Engels op. cit. 83). Had functionally anything gone wrong (except for the one thing that did go wrong, which was Darius died before Alexander got to him), Alexander would have been in dire straits indeed.

Caesar was, of course, uncommonly good at this (with Dyrrhachium in 48BC being the one very notable time things don’t quite work out), but that disguises the complex web of calculation, map-reading (or scout-reading) and guesswork that goes into it. Most Roman generals, lacking Caesar’s skill, tended towards more careful and methodical campaigns which were the slow road to a certain victory; one of Rome’s notable advantages was the regularity with which it produced reliable if unexceptional generals who managed the difficulties of logistics and movement fine, if not exceptionally. It takes only a brief glance at the difficulties of Marcus Antonius, Caesar’s protegee, to see why this was valuable: Antony tries again and again to pull off bold, Caesar-like campaigns and really only succeeds once (Philippi in 42). Antony has a reputation in the sources as bull-headed and impulsive in contrast to Caesar’s bold but calculating nature and it really comes out in their campaign abilities; Caesar’s dice always seem to come up just right (too many times to assign to pure chance) whereas Antony takes similar risks and more frequently fails. The difference between their decisions was often very small (indeed, in many cases Antony appears to be taking the exact same risks) but at the ragged edge of the possible in logistics, a slight miscalculation can bring catastrophe.

Still from HBO’s Rome, the Battle of Philippi. Antony, on the left, is enjoying the experience of having a bold lunging march out of safe supply to force a quick victory against his opponent work for the one and only time this gamble will pay off for him. Agrippa (right) is presumably thinking about all of the ways he can exploit this weakness in Antony, a thing he will do in 31 BC.

In the end, I think there is some good sense to Clausewitz’ argument (drink!) that warfare cannot be boiled down to mere numbers – there being too many unknowns – and that what separates a serviceable general from an excellent one is the ineffable quality of being able to instinctively take in the situation and make the right risks, what Clausewitz terms ‘genius.’ At the same time I cannot help but note that for all of the flashiness of Caesar, the Romans rarely had brilliant genius; what they had a lot of was workmanlike generals whose military-political careers (those being conjoined in the Roman world) had prepared them for the difficult administrative task of making the army go, of managing marches, supplies, foraging and so on. Roman elites serves after all first as military tribunes (who frequently led foraging parties), then as quaestors (who managed supplies and pay),10 then later as praetors in command of smaller armies before being consuls in command of big armies (and of course the fact that all of these Roman elites also managed large estates with huge – frequently enslaved – workforces must also have prepared them). A steady supply of solidly adequate generals backed up by a superior military system – mostly superior in mobilization rather than actual fighting – was enough.

Meanwhile on the other end of the spectrum you have generals whose over-sized armies seem to wallow, practically paralyzed by the herculean effort to merely get them moving. As a younger student, I always found myself puzzled by this – how hard can it be to just march in a direction? Is the general just lazy? But what I hope you can see in this series is that there is actually quite a lot going on to keep a large army moving. A mediocre general (or a general with medicore subordinates or staff) with a very large army may find themselves overwhelmed by the coordination demands it imposes – who marches where? When? On what roads? How do you make sure they don’t run into each other and that there is enough food locally for each group? Who takes the front? At what rate of march? And what do you do when invariably units that you cannot directly observe (because the army is very big) move slower than you need or get lost? On top of this the general has to be managing the direction of march and also the supplies of food as well as the deployment of foraging parties. The number and complexity of these moving pieces only increases as the army gets larger, while the hours in the day for actually marching decreases as the army train lengthens, and so the army just crawls along, paralyzed by its own bulk.


Consequently, going back to where we began this series, while the general of a pre-industrial army has at best only limited control over how it fights in battle, his control over the army in the marches before the battle is much more extensive and coordination in this phase can shape the battle or siege to come. Because foraging and supply concerns are directly connected to army size, a military system (or individual commander) that is better at managing these issues can push larger armies further out, opening up new opportunities in the campaign space. By contrast a system (or general) that is poor at this kind of thing will be forced to accept either a smaller army or else may end extremely limited in options: either unable travel certain key routes with insufficient supplies or population or else functionally paralyzed by the size of the army itself.

Of course related to this the general mismatch between the size of armies and the states that fielded them in Europe during the early modern period (esp. 1500-1700 or so) made those armies increasingly destructive. As the transition to gunpowder warfare pressured states to deploy larger infantry contingents in their armies, the logistics systems which had worked in the late Middle Ages buckled under the strain, leaving the soldiers in question to supply themselves locally, with the catastrophic results we discussed in part II. Consequently while the increased effectiveness of these large armies was clearly welcomed by their rulers, by the mid-1600s it obviously became clear to European monarchs and their generals that the destructiveness of these forces had become an intolerable hindrance, leading to the (re)establishment of centralized state logistics in Europe which would in turn both motivate and feed off of increasing administrative capacity which in turn leads towards the establishment of the modern administrative state.

Finally, while this last post has been mostly focused on this question once again from the perspective of the general, we must also keep in mind that even well-run armies caused substantial misery among the rural population as they moved. Even an army not trying to cause damage, by pulling in such a massive amount of the local surplus, could push local communities into hardship. At some point we may come back to actual strategies of devastation apart from foraging, but of course if armies could push peasants to the brink merely by being around, they could do even worse if they actually intended to cause damage (though ironically the upper-limit to this sort of damage was often limited by the small size of these armies; administrative capacity cuts both ways and the very things that have made more modern armies capable of causing less damage merely by existing have made them more capable of causing much more damage by intent).

The ‘background noise’ of pre-industrial warfare was thus looted barns and crowded roads; the army had to do these tasks in order to sustain itself on the march, the general had to coordinate these tasks in order to keep the army moving and the rural population had to endure these tasks in order to survive.

  1. I should note, I am going to refer here to our imaginary general with masculine pronouns. Women commanding armies in this period in the broader Mediterranean was not entirely unknown but it was exceedingly rare; even in most societies where women might rule in their own name it was very common for army command in the field to be delegated to a male subordinate (women commanding the defense in the event of a siege was more common, though still rare). Again exceptions exist: Artemisia of Caria, Aisha at the Battle of the Camel, Matilda of Tuscany, etc., but only a relative handful over a very long period with very many army commanders. So it seems reasonable to use masculine pronouns for an occupation that was in this period performed overwhelmingly by males, though that does not erase the small number of women who did command armies, thus this footnote.
  2. Lots of adjustments here: they need 365-person-days of grain to survive per year, but there will also be fodder for animals and some small surplus for sale. On the other hand, the nutritional needs of an average soldier are much higher than the nutrition needs of the average rural person – which after all includes women and children with lower calorie demands (high activity adult male might require upwards of 3,500 calories per day where children, the elderly an less active folks might be below 2,000). I’m working my numbers from a model of a smallholding Roman farming family that I developed for my current book project.
  3. In Peasants, Citizens and Soldiers (2012)
  4. Of the actual flaming kind, not British flashlights
  5. Unsurprisingly, one of the few ancient Mediterranean polities to do this with any regularity and success were the Romans. This comes out very clearly in Julius Caesar’s campaigns in Gaul and also in the lead up to the Battle of Philippi, where in the latter case the armies were absolutely too large to march as a single formation. That said the Romans still only did this from time to time; for the far more common use of these kinds of operations in the pre-modern period one must look to the Steppe.
  6. “Why is Athens here?” So the Sicilian Expedition is a really big (and very disastrous) overseas operation, but seems to have dealt with supplies locally. The reports of reinforcements include men, horses and money, but not massive amounts of food. In practice the Athenian army was of a size that could be supported on the relatively rich grain-lands of Sicily. On the flip side, one might argue that provisioning the city of Athens substantially by sea during the Peloponnesian War is a feat sufficient to merit inclusion in this list and I tend to agree; thus Athens’ inclusion.
  7. This effort is treated in detail in P. Erdkamp’s masterful Hunger and the Sword (1998), which is, alas, very expensive.
  8. Which matters, to be clear: soldiers need a ‘theory of victory’ to sustain morale. ‘We bottle up Hannibal here until everyone involved dies of old age’ is not going to inspire anyone to put up with hardship, but ‘We hold Hannibal here while Scipio and his army sock it to the Carthaginians in Spain and Flaccus and his mates slowly reconquer southern Italy’ is much better.
  9. But this, this ain’t it, chief.
  10. At least in the Middle Republic. Caesar’s quaestors seem not to do this, curiously – something that may have to do with Caesar’s manifest near total command and logistics independence on account of being at odds with much of the Senate.

278 thoughts on “Collections: Logistics, How Did They Do It, Part III: On the Move

  1. So about those Roman soldiers back at camp whose turn to march hasn’t come yet – are they doing anything or just waiting? Do they get to sleep in since they don’t start until noon? Are they standing in their serried ranks while playing word games like Would You Ever and I Spy? Can they leave the unit for a quick crap? Got a lot of questions about the guys in the back of the marching column.

    1. My guess would be that the units to move out last (which would be rotated day by day) would be tasked with the lion’s share of breaking camp; while the first units to move out would cover setting up camp at the destination.

    2. Since each tent group seems to have carried their own stakes, personal effects, etc, I assume anyone leaving the camp “late” or in the back of the column would have spent time doing such tasks as were communal in breaking camp. Things like filling in latrines, or pulling down watch towers erected during the night.

    3. This almost certainly varied from one Roman army to the next. I can easily imagine that the best-administered ones could dispatch the earliest maniples or cohorts in the order of march (probably decided the previous night, or according to a rotational scheme determined up to a week before at the previous full-day halt) before the trailing units had even finished breaking camp, while less well-administered ones might need most of the army to be lined up in the order of march (just to make sure that there had been no administrative fuck-ups within the past few hours) before the lead units of the main body could even set off. And yes, in the latter case this probably meant standing or sitting in marching formation for hours on end. After all, modern motorised forces still often end up sitting around in their convoy sequence for hours before the convoy commander gives the signal to hit the start point/start line — and for very similar reasons.

  2. The logistics are so insanely favorable for water transport (62 metric tons of food and fodder a day, meaning that a single Roman era ship could carry 3-4 days worth of the army’s provisions) that it honestly surprises me that there wasn’t a much huger emphasis by ancient rulers and societies on building navigable canals and waterways literally wherever it was possible for them to do so with their existing technology. That is just a massive advantage if you can pull it off.

    1. Building navigable canals is a huge capital investment, and maintaining a canal in navigable condition is hard. This is easily visible: England has excellent geography and geology for constructing canals, but when they were no longer needed, the canal network detoriorated quite rapidly. And in England, you have a lot of small rivers separated by relatively low hills, and cutting through the local stone is easy.

      In large parts of Europe, canals need be quite large to be of any use. Thus, you need a unified state to construct them, both for financing and for security of work and navigation. For example, the major canals in France and Prussia could only be built in the 17th century. In addition, if the bedrock is not chalk but e.g. granite, you can’t really build canals without explosives, and long canals also require good geodesy: you need to really have an understanding of ground levels when embarking on a canal project. (I would say this was the greatest obstacle in ancient world for long canals.)

    2. To elaborate the other comment: Building canals was hard. It requires a really high state capacity, not only to build it but also to maintain it – if the water in a canal comes from a major river, then there is a high chance the sand in the river would clog the canal within decades – in addition to that you also need favorable terrain.

      Ancient China was able to construct massive canals because 1. China was a big empire and therefore had the state capacity 2. the entire Chinese plain is a floodplain thus much easier to dig ditches.

      Even then canals were costly for the Chinese empires. The Mongol Yuan Empire tried to dig the Grand Canal through the hilly country in Western Shandong with forced labor, ended up with a peasant rebellion that overthrown their rule. The following Ming Empire eventually finished the Grand Canal; however the embankments of the Canal blocked Yellow River (and many smaller rivers in the region) from draining properly, caused massive flooding outside the Canal almost every year. This geoengineering failure of the Grand Canal eventually produced a huge displaced population, participated in numerous rebellions that shook the imperial rule, their diaspora into other Chinese provinces continued way into late 20th century.

      And that was why most of the pre-modern state-level polities did not even try canal building.

      1. Pre-modern States weren’t really knowledgable about the environment and ecology. To even properly implement the Canals whilst ensuring proper flows of water to the sea and to prevent erosion and flooding.

        And having trees to anchor the soil for example.

        So Canals if they are to be built they must take the environment and ecology into consideration to be done properly.

    3. As noted in one of Bret’s other posts, in pre-industrial societies the RoI of wars of conquest was much greater than that of infrastructure improvements. The time frame of large canal projects is mostly too long for elites to support them: why invest in building a canal that will take decades when you can just invade some other place and take their stuff?

        1. Quite possibly. China was known as “The Middle Kingdom” because to the north you had Siberia, to the east ocean, to the west steppe, desert and mountains. To the south, attempts to expand into Annam kept running into power/distance limits as what is now northern Vietnam kept coming into and out of control by China.

          1. The mighty Qing Chinese army got defeated because of bad logistics, lack of preparation and disease in South East Asia.

            Not even the greatest war machine can function without fuel.

  3. > In practice we’re actually still being a bit too nice to our army: we’re assuming they march every day. But while humans can more or less do that, pack and draft animals cannot. In practice for a sustained march these animals need to be rested one day out of six or so or the strain will render them useless in the long term.

    Wait a second! I think this is where 7 day weeks come from! The “week” phenomenon has been observed over thousands of years and many continents. Wikipedia seems to connect this to moon phases, and celestial bodies.

    But there’s a simple possible explanation why the concept of ‘week’ is so widespread. It’s not so that *humans* can rest, it’s because pack *animals* and beasts of burden must rest.

    1. The Wikipedia article shows that the 7 day week likely diffused from the Near East, probably from the original Babylonian one linked to lunar phases. Japan and China have domesticated animals and yet the article makes clear the 7 day week was adopted from elsewhere and not independently invented. The article also mentions that other societies with domesticated animals had weeks of different lengths, such as the 10 day week of ancient Egypt and China.

  4. In Poland we have a saying: “Jak nie urok, to przemarsz wojsk.” Translation: “If not evil eye, then marching armies.”

    This is used when someone has a streak of bad luck.

  5. Now I think that the Roman habit of setting up a fort each time they went to bed was as much about defense as about limiting damage to civilian population.

    1. The fort is discussed here, and defense is the main reason. But protecting civilians/reducing the mischief soldiers can cause is a good bonus, or a good additional reason, to build a fort.

  6. Saladin’s 1189 campaign is an excellent example of what happens when an invading army (burdened with a siege train intended for Jerusalem, and operating in late October) is defeated in detail – though in this case, the opposing army struck at the much reduced marching force, not the numerous and large foraging parties. Saladin’s main force was held up crossing a flooded wadi (re: siege train) near Montgisard when attacked by forces breaking out from fortresses to the rear of the line of march combined with an arriere-ban. Much of Saladin’s army was still in line of march when attacked, IIRC, and his superb Mameluke cavalry barely had time to form up before being charged. Please note that Saladin was and still is considered a good general, but in this case too dismissive of his opposite number – the sick and teenaged King of Jerusalem. Because this battle left the main force broken and the foragers unable to recombine, and surrounded by hostile fortresses, the army is supposed – by Arab historians – to have lost 90% of its men on its flight back to Cairo.

    1. 90%? Oof. Though I suspect some of those were deserters who faded back into the population. This isn’t something like Napoleon’s retreat from Moscow, as I understand it; fleeing soldiers splintering off the defeated army would be able to find refuge much more quickly and after traveling much more reasonable differences.

  7. I don’t understand why the different parts of the army need to camp in the same place. If they all just camped where they happened to be at the end of the day’s march you could avoid the problem of the rear waiting for the front to leave and the front waiting for the rear to arrive. That would also alleviate part of the tyranny of the wagon equation.
    I guess a single camp is more defensible, but that shouldn’t be a problem in friendly territory and camping dispersed wouldn’t leave you any more vulnerable than you had been on the march.

    1. Some possibilities:
      *The camp needs to be near a water source, because all the men and animals need to be near a water source
      *Coordination would be a problem – if the men and supplies are spread out over five or ten miles, how do you tell the rear units where to go?
      *In friendly territory, more dispersed men are harder to prevent both from deserting and from stealing things and otherwise causing trouble

    2. There us no such thing as safe territory on campaign,
      If you got assaulted in the evening. unlikely , or in the morning with weaker forces, you would be lucky there is something left resembling an military unit after the battle.

      You would need more guards, many more guards and you would have weaker fortifications if any

          1. Remember, if there are fish and game in sizeable quantities in the surrounding countryside, the odds are good that the peasants are already hunting and eating them as part of their subsistence.the army confiscating much of the village’s grain does. A big army of well armed men riding through and killing every sizeable game animal they can catch causes problems for the same reason

  8. From a random internet person (ok, random internet person writing a dissertation on the 30 years war):
    “Bear in mind that everyone involved is moving very slowly. The field glass isn’t even used yet; you figure out where the opposing force is by sending out light cav or looking on the horizon for a plume of dust. The artillery, as the most honorable and important branch, has the first right to the roads, which means that everyone else, if they’re on the same track, moves at the pace of the slowest gun. Remember when I said that the Army of Flanders–well-trained, well-organized, very proud–moved at four and a half miles a day? This amazed contemporaries.”

    That part about artillery sounds… interesting. I guess the army couldn’t exactly leave it’s cannons behind anyway, but having them in the front doesn’t sound very handy.

    1. Total non-expert here, but my interpretation is:

      If the road is too crowded, so someone has to move off-road, make sure that it’s not the artillery; they’re slow enough as it is. However, giving the artillery priority on road-use doesn’t mean they’re the only ones on the road; you’re going to have someone else in front of them and behind.

    2. It makes a kind of sense, I suppose. I don’t know about “most honourable and important branch” (17th-century artillery was still relatively ineffective in field engagements, though essential in sieges) but it was almost certainly the most *expensive* branch, pound for pound, the most vulnerable, and the hardest to replace. It had a prestige, too, with capture of guns in battle being a means of calculating victory.

      Logistically, though, you don’t want your guns to be left behind, as they might be if the infantry and cavalry go on ahead, and having them at the back of the column presents other difficulties: when you reach your destination – be that a meeting engagement, pitched battle or a siege – you want your guns to be in action as quickly as possible. If they’re at the front, they can start setting up and be ready to fire by the time the rest of the army comes up behind them (and cavalry can if necessary advance quickly ahead of the guns to screen them while they do so). If you have them further back, your forward divisions of infantry and cavalry are either standing around waiting for the guns to arrive before they can take action, or they’re engaging in battle without artillery backup.

      I would imagine that’s at least some of the thinking behind it, if true, but I don’t know whether that was the actual reason or indeed whether it happened as described.

    3. On top of the issues others mentioned here, it’s worth remembering that a marching army would put much more strain on a road than almost anything else imaginable, and that many roads of this era were unpaved with at most crude structural reinforcement.

      By the time twenty thousand soldiers, several thousand horses and mules, and several hundred wagons have got done traveling down a dirt road, the road isn’t in very good condition. If you try to put heavy artillery units in the back of an army like that, they’re going to have even more problems making headway than they would at the front of the army. Their heavy wagons and wheeled gun carriages are constantly running into trouble dealing with someone else’s wheel ruts, patches where the dirt has been trampled into mud, and so on.

      So by the time the infantry and cavalry have moved as far as they can, the artillery is miles behind. That, or the infantry and cavalry are spending the majority of their time sitting still waiting for the artillery to catch up, defeating the purpose.

    1. How did logistics and operations factor into it? I thought it was a case of a formation army getting caught in the worst possible circumstances for formation fighting by an army of melee fighters.

      1. Sorry, should have researched this better first. Apparently the Romans were caught strung out along a narrow road.

      2. Strung out along a narrow road, probably more a track in the forrest then a road, on the march to the winter quarters, probably in an area chosen to offer as little opportiunity to forage as possible.

        1. The Romans were basically squeezed between a deep march, and a large cliff face. Also past pre-prepared enemy (Germanic) field fortifications (low walls with palisades on top, and numerous small sally ports). If, and when, the Romans were able to counter-attack, they would be up against walls, which they were not prepared for, and would be continually harassed in back and rear by other enemies.

          1. If you are refering to the Kalkriese site, I have been there. Yes, the hill is quite steep, but calling it a cliff is overselling it.
            But yeah, the final battle field was prepared in a way, that made it basically impossible for the romans to get into their time tested formations. And our sources tell us, that their usual operation where already hampered with the days before.
            And I would expect that Arminius as the comander of the auxilary light cavalry, further upset foraging. And maybe already chose a route that would offer less foraging then optimal.

  9. Thank you for (yet another), very illuminating series.
    This one particularly took me way back then, to my time as a teen reading Sir Runciman’s books on the Crusades, taking me more than a few stops and rereads to get it and realize it was NOT fantasy fiction. And in going through the early chapters quite a few times it really was striking just how violent the treks from Peter the Hermit’s ‘rabble’ or the various nobles that followed would get even at such a distance from their stated goal in the Holy Land, more than a few completely sidetracked or destroyed in the process.

  10. This grammar clunks: “Roman efforts against Hannibal in southern Italy after Cannae (so from 215-203) as a master-piece of this kind of maneuvering.” Great series!

  11. Excellent series on pre-industrial logistics. The Peninsular War of 1807-14, fought in lands with few roads — even fewer capable of wagon traffic — and few areas of highly productive agriculture, provides examples of every concept in the series. Napoleon’s Marshals could have learned much from Marshal Villars.

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