Logistics of army on march

[Aldarion]

Can somebody check the following?
--------------------
For a two-week march, a 15 000 men force requires 288 400 kg of grain for soldiers' rations (307 600 kg for 16 000 men force). Horses and mules significantly increase this – while light horses used by scouts and rangers can subside entirely off the grass, large war horses require a supply of food, around 15 kg per day, while normal war horse requires 10 kg per day, and same for pack or draft horse, while mule would require 7,5 kg per day. Further, each cavalryman has to have a war horse, a riding horse and a pack horse. 5 000 cavalry in usual legion thus requires 15 000 horses, of which 2 000 heavy war horses, 8 000 average-sized war or riding horses, and 5 000 pack horses or mules. Assuming mules instead of pack horses, these would require a total of 147 500 kg of fodder per day or 2 065 000 kg for two weeks. Total requirements for a legion come for 2 372 600 kg over two weeks.

A standard pack horse or a mule can carry a maximum of 120 kg over any distance. For a two-week march, a mule would carry 105 kg of barley for itself, leaving 43 kg free. Since soldiers can and do carry 14 to 17 days worth of food with themselves on the march, barley carried by mules would be that required by animals themselves. As such, a 16 000 strong legion on a two-week march would have 2 065 000 kg of barley carried by pack animals, requiring 48 023 mules. Army accompanied by pack animals can make 25 km per day, or 350 kilometers with above numbers. Oxen however would require no fodder, as they can obtain food by grazing; this however requires significant time, and may not be useful in mountainous areas. Even so, 2 000 oxen can be driven no more than 15 men. In flat areas, two mules can pull a wagon carrying 660 or cart carrying 500 kg. Two mules would require 210 kg of fodder for two weeks, leaving 450 kg for a two-week march or 240 kg for four-week march. As such, army would require 4 589 wagons for two week march (280 – 350 km) or 8 604 wagons for four-week march (560 – 700 km). These would require 9 718 or 17 208 mules – former number being mere one fifth of number required in mountainous areas. If using carts – of lesser capacity but more agile in hard terrain – numbers are 8 181 carts for two-week march and 29 658 carts for four-week march.

Water transport is far more efficient than overland transport. Large sailing ship can carry 900 tons of grain, with 600 tons for hulk-type ship and 300 tons for cog-type ship. Smaller ships used for riverine transport carry 20 to 30 tons.

State warehouses receive goods collexted as tax, many of which are used to support the army, as inland thematic lands and warehouses provide food, fodder and basic supplies. Special logistical troops obtain mules and other pack animals. Heavy infantry regiments are provided with one mule per pair of soldiers. Supplies from warehouses may be supplemented by supplies shipped via rivers.

 

[CupofJoe]

One thing to bear in mind is that Horses [and I think Oxen too] can't walk and eat. They can do one or the other.
I'm fairly sure that horses can survive on just grass either, but I'm a lot less sure of the.
You don't give a time/technology frame to base things in, so I'm assuming your maths is right but I don't have the knowledge to know if they are accurate.
Two things that do look odd to me.
The first is 14-17 days of food carried by each soldier. That seems a lot. I wouldn't want to carry 14+ days worth of MREs... [I like the idea of having mules around for the haulage]
The other is 2000 oxen driven by 15 men. On a cattle drive, that sounds about right but in the middle of an army and I'm guessing you will need more.
Unless logistics and supply lines are intrinsic to your story, I'd go for a bit of handwavium and avoid using any specific numbers.
Buried deep in one of the threads going back years [2013?] was an attempt to work out a formula for how many pack horses were needed for an expedition [ X people over Y days ]. And that was complicated enough.

 

[Aldarion]

One thing to bear in mind is that Horses [and I think Oxen too] can't walk and eat. They can do one or the other.

I know.

I'm fairly sure that horses can survive on just grass either, but I'm a lot less sure of the.

From what I have found, smaller horses can survive on grass just fine. Large war horses, especially heavy cavalry chargers, cannot.

You don't give a time/technology frame to base things in, so I'm assuming your maths is right but I don't have the knowledge to know if they are accurate.

Technology is Early Modern period, as I am basing a lot on Ottoman-Hungarian and Ottoman-Croatian wars, so 1450s to 1490s.

Two things that do look odd to me.
The first is 14-17 days of food carried by each soldier. That seems a lot. I wouldn't want to carry 14+ days worth of MREs... [I like the idea of having mules around for the haulage]

Keep in mind that ancient/medieval/early modern soldiers did not spend nearly as much time in combat as modern soldiers, so they had less caloric intake on average. OTOH, they did walk everywhere.

Anyway, I took number from some book I found on google books. I cannot find the original source, but I found this:
Roman Armor, Legionary Weapons and Equipment | UNRV.com

IIRC, ration would be 2,5 lbs per day, so 14 days is 35 lbs. Civil War soldier would carry 35% of body weight and Roman soldier 50% of body weight. So if we assume 150 lbs weight for a soldier (bit on a light side, maybe, but most soldiers would not be large guys, especially if they have to walk everywhere), that gives weight of 75 lbs. Even full plate weights no more than 30 lbs, so adding weapons (10 lbs total for warhammer, sword and spear), soldier can still carry up to 35 lbs. Keep in mind that of that, leg armour would be cca 10 lbs (maybe little less), so carrying capacity would be more for an infantryman utilizing half-plate or 3/4 plate armour.

The other is 2000 oxen driven by 15 men. On a cattle drive, that sounds about right but in the middle of an army and I'm guessing you will need more.

True. Question is also do you need specialists to drive oxen, or not?

Unless logistics and supply lines are intrinsic to your story, I'd go for a bit of handwavium and avoid using any specific numbers.
Buried deep in one of the threads going back years [2013?] was an attempt to work out a formula for how many pack horses were needed for an expedition [ X people over Y days ]. And that was complicated enough.

Problem is, it will be largely a story about warfare, so logistics are kinda important.

 

[skip.knox]

I echo CupofJoe. Sure logistics are important, but that's not quite the issue. The issue is, does the reader need to know all these numbers? We know Caesar could cover forty miles a day in a sustained manner--that's how he spooked Pompey out of Italy. We also know a fair amount of rate of march for the Ottomans and other armies in that period. So, as long as you're in the neighborhood of verisimilitude, why try for exact numbers (which will prove elusive anyway)?

OTOH, if it's just plain fun to calculate and speculate, I get that.

 

[Aldarion]

I echo CupofJoe. Sure logistics are important, but that's not quite the issue. The issue is, does the reader need to know all these numbers? We know Caesar could cover forty miles a day in a sustained manner--that's how he spooked Pompey out of Italy. We also know a fair amount of rate of march for the Ottomans and other armies in that period. So, as long as you're in the neighborhood of verisimilitude, why try for exact numbers (which will prove elusive anyway)?

OTOH, if it's just plain fun to calculate and speculate, I get that.

Reader most likely doesn't need to know. But since stories will be about war and military strategy, I need to know how various factors, including armies, will interact - and this includes their capabilities and limitations. I cannot have a medieval army - even a semi-professional one - marching around as if it is a modern army with motorized logistical network - or else a robot army running on fusion batteries or something. One of things I enjoyed the most in Lord of the Rings was the impact of logistics: the fact that Rohirrim could not just mount up and leave, and that it actually took them time to get to Minas Tirith; that Gondorian messanger took time to assure Theoden that Minas Tirith had enough supplies to feed Rohirrim when they arrived as well; that we see actual farmlands surrounding both Helm's Deep and Minas Tirith; that Tolkien actually discussess logistics in Disaster of Gladden Fields. (EDIT: Good discussion here). These are all small things, but they make the story feel more real to me; and seeing how I always had an interest in military history, background stuff - even if merely hinted at - is just as important to me as actual story (albeit it being fun definitely doesn't hurt either). I was never able to forgive D&D for teleporting armies in Game of Thrones or Christopher Paolini for his mechanical horses that apparently run on fusion batteries present in Eragon. EDIT: Well, they could have been zombie horses. Shows you the advantages of an undead army.

 

[pmmg]

There are a lot of numbers to sort through in that. The Art of War, by Sun Tsu has some good insights into this if you convert the numbers. I figure he had an idea of what it took. Also RPGing aides out to be a good resource. They try to get it right.

I think if I am reading a book and I am focused on were there enough mules to get the job done, the story is in trouble.

OTOH, I don't fault a writer for wanting the details to be right, even if the reader does not know. If I was to figure out the details were not right, I might lose trust in the writer.

 

[skip.knox]

Yeah, I think it was the numbers that misled me. It sounded like there was an attempt at specificity. All I'd aim for would be to establish parameters.

I did this with Goblins at the Gates. I needed to know how long it would take to get a Roman frontier legion (4thc) across the Danube. Because, you know, the goblin horde was coming. In the end, all I really needed was can they get across in a day or will it take multiple days. It's not the crossing itself that's crucial, it's that as the hours pass, more and more of your soldiers are on that side of the river while fewer and fewer are on this side of the river, until it gets to the point where those remaining are pretty much guaranteed to be annihilated. I wound up deciding to employ some other ploy to delay the goblins long enough to get everyone across, because no matter how I sliced it I wound up with a brave few being killed so the last raft could get away. And how could my hero not be among those brave few? And then the story ends too early.

So, while learning about numbers was interesting, and did establish some general parameters (and I learned a bunch about rafts and ferries), in the end it didn't matter much. What mattered was what the story needed.

 

[Aldarion]

There are a lot of numbers to sort through in that. The Art of War, by Sun Tsu has some good insights into this if you convert the numbers. I figure he had an idea of what it took. Also RPGing aides out to be a good resource. They try to get it right.

I think if I am reading a book and I am focused on were there enough mules to get the job done, the story is in trouble.

OTOH, I don't fault a writer for wanting the details to be right, even if the reader does not know. If I was to figure out the details were not right, I might lose trust in the writer.

Precisely. As I said, I would never be able to forgive a writer for (implied) mechanical horses or sunlight-powered army. Doesn't mean reader needs to be bored with all the numbers, but if you have a medieval human army, you cannot just have them appear at a place five hundred kilometers away in five days.

Yeah, I think it was the numbers that misled me. It sounded like there was an attempt at specificity. All I'd aim for would be to establish parameters.

I did this with Goblins at the Gates. I needed to know how long it would take to get a Roman frontier legion (4thc) across the Danube. Because, you know, the goblin horde was coming. In the end, all I really needed was can they get across in a day or will it take multiple days. It's not the crossing itself that's crucial, it's that as the hours pass, more and more of your soldiers are on that side of the river while fewer and fewer are on this side of the river, until it gets to the point where those remaining are pretty much guaranteed to be annihilated. I wound up deciding to employ some other ploy to delay the goblins long enough to get everyone across, because no matter how I sliced it I wound up with a brave few being killed so the last raft could get away. And how could my hero not be among those brave few? And then the story ends too early.

So, while learning about numbers was interesting, and did establish some general parameters (and I learned a bunch about rafts and ferries), in the end it didn't matter much. What mattered was what the story needed.

Your brave hero can be not among those last few simply by not being in a unit that holds them off. Though that may not be interesting for a story.

Yeah, I agree that what it matters is what the story needs. But if the story is about war, then author at least needs to know logistics, as it will affect the storyline - the timeline, the environment, actions and decisions of both sides. To give the example of Tolkien, if you look closer you can see logistics at work everywhere: Sauron needs time to build up his strength before the attack, and when he is forced / incited to attack too early, he is defeated. Attack comes from Minas Morgul, because it is the only major base close enough to be available. Sauron has to attack Osgilliath and Cair Andros, because otherwise he cannot supply his army at Pelennor. Denethor and Faramir do not have the forces to defend indefinitely, so Faramir has to fight a delaying action to give time for survivors from Cair Andros to reach the city. Minas Tirith is noted as being surrounded by farmlands - as a medieval city ought to be - and this too affects the story, as Rohorrim cannot charge as a single mass (as they do in the movie). Rohan's army is small enough that it can still move and be supplied as a single unit (it is about the size of a Principate Roman legion). Etc. etc.

EDIT: Speaking of which, is 16 000 men too much for a medieval / ancient army unit? This is my organization right now:

Legion (legio, meros)

Each legion is assigned one province which supports it, from a total of 18 provinces. Prescribed number is 2 000 heavy cavalry, 2 000 light cavalry, 3 000 heavy infantry, 4 000 crossbowmen and 1 000 shield bearers, for a total of 12 000 troops in main battle line, of which 4 000 cavalry and 8 000 infantry. In addition, legion will have 1 000 javeliners and 1 000 slingers acting as skirmishers, as well as 1 000 light infantry and 1 000 light cavalry acting as scouts and skirmishers, bringing a total to 16 000 men. To this are added staff, which at total of 20 cohorts (see below) counts 220 men.

Additional 200 light cavalry and 400 light infantry is supported from same area but forms independent cohorts tasked with ranging and garrison duties.

Cohors (cohors, tagma)

Cohors can be of two types: thousand-man cohorts (cohors milliaria) and 500-man cohorts (cohors quinquagenaria), albeit actual numbers are not exact. Cavalry cohorts are called alae. Cohors equitatae are not cavalry cohorts, but rather mixed cohorts of ¾ infantry and ¼ cavalry. Each cohort has a tribunus (commander), vicarus (assistant commander), adjutor (clerk), optio (quartermaster), surgeon, two heralds, two standard-bearers (draconarii), a trumpeter and a drummer.

Typical infantry cohort is 300 heavy infantry, 400 crossbowmen and 100 pavesarii. Cavalry cohort is 200 heavy cavalry and 200 light cavalry. Skirmisher cohort is 500 men. Independent cohorts have 200 light cavalry and 400 light infantry each.

Centuria (centuria, kentarchia)

Centuria has hundred men.

Decuria (decuria, kontoubernion)

Decuria has ten men. As each decuria shares a tent, it is also called contubernium.

The reason why it is in multiples of ten is basically logistics, but might be I should halve a legion to five cohorts.

 

[Aldarion]

Changed it a bit due to modified unit sizes:

EQUIPMENT AND LOGISTICS

Equipment is provided by guilds of fabricenses. These are either state- or privately- -owned guilds that are given allowance by the emperor to produce weapons for the army. Soliders purchase equipment with income they receive from their lands, or else from their own wage. A system of factories (fabricae) allows for standardized equipment production. These lay either on major waterways, or else close to sources of raw materials. Specialized fabricae, called clibanaria(e), produce plate armour for heavy infantry and cavalry as well as cavalry equipment. These are overseen by Master of Offices (magister officiorum). Each group of workers is responsible for monthly quota of objects they produce. Soldiers have to buy equipment themselves, and equipment is often procured locally.

Logistical apparatus is overseen by praetorian prefect, who is responsible for liasing between army and provincial officials. Where possible, goods are procured locally, but in friendly territory there are necessary limits to army's self-sustinence. Thus well-maintained roads – via millitaria – are of vital importance. These are eight meters wide. By law, minor public roads have to be 16 feet (4,8 meters) wide, but some roads are up to 8 meters (26 feet) wide. When in friendly territory, logistical apparatus of each province is required to provide for an army that passess through it. If an army is too large for resources of one province, neighbouring provinces may be mobilized as well. Provincial officials are given an advance notice of army's requirements in foodstuffs and other goods, which are then deposited at named sites (fortified granaries and storehouses) along the army's route of march. These are then collected as tax-in-kind, and thus counted against next year's tax, which is reduced by a recorded amount. If more goods are collected than is due for tax the next year, then extra goods are paid for in coin (this system is known as coemptio). Supplies from warehouses may be supplemented by supplies shipped via rivers. Special logistical troops obtain mules and other pack animals. Heavy infantry regiments are provided with one mule per pair of soldiers. If army arrived into district which was not warned in advance, soldiers are sent out to buy their own supplies.

For a two-week march, a 15 000 men force requires 288 400 kg of grain for soldiers' rations - 115 360 kg for a standard 6 000 men force. Horses and mules significantly increase this – while light horses used by scouts and rangers can subside entirely off the grass, large war horses require a supply of food, around 15 kg per day, while normal war horse requires 9 kg per day, and same for pack or draft horse, while mule would require 7,5 kg per day. Further, each cavalryman has to have a war horse, a riding horse and a pack horse. 2 000 cavalry in usual legion thus requires 6 000 horses, of which 800 heavy war horses, 1 200 average-sized war horses, 2 000 riding horses, and 2 000 pack horses or mules. Assuming mules instead of pack horses, these would require a total of 59 000 kg of fodder per day or 826 000 kg for two weeks. In normal conditions a third of figure for animals is barley, which means animals will require 275 000 kg of barley over two weeks, for a total of 390 360 kg over two weeks. If there is no possibility for grazing at all, total requirements for a legion come for 941 360 kg over two weeks.

A standard pack horse or a mule can carry a maximum of 120 kg over any distance. For a two-week march, a mule would carry 105 kg of barley for itself, leaving 15 kg free. Ridden cavalry horses would carry 34 kg of barley, unridden cavalry horses 68 kg of barley, and mules 84 kg of barley. Since soldiers can and do carry 14 to 17 days worth of food with themselves on the march, barley carried by mules would be that required by animals themselves. Horses themselves would carry 204 000 kg of barley. As such, a 6 000 strong legion on a two-week march would have 737 360 kg of barley carried by pack animals, requiring 6 145 mules. If grazing is available as an option, barley carried by pack animals is 186 360 kg, requiring 2 219 mules.

Army accompanied by pack animals can make 25 km per day in flat terrain, or 350 kilometers with above numbers. Oxen however would require no fodder, as they can obtain food by grazing; this however requires significant time, and may not be useful in mountainous areas. In flat areas, two mules can pull a wagon carrying 660 or cart carrying 500 kg. Two mules would require 210 kg of fodder for two weeks, leaving 450 kg for a two-week march or 240 kg for four-week march. As such, a legion would require 868 – 2 092 wagons for two week march (280 – 350 km) or 1 626 – 3 922 wagons for four-week march (560 – 700 km). These would require 1 736 to 7 844 mules – former number being mere one fifth of number required in mountainous areas. If using carts – of lesser capacity but more agile in hard terrain – numbers are 380 (with grazing) – 1 504 (no grazing) carts for two-week march and 2 330 (with grazing) – 9 217 carts (no grazing) for four-week march. Four-week march is standard which provincial officials have to set aside for an army.

Above limitations however only really apply for armies that have more than one legion present, as an individual legion is small enough to feed itself through foraging when in enemy territory. Even so, foraging is one of riskiest activities of an army, as foraging parties could be attacked, or else fail to acquire enough supplies.

Water transport is far more efficient than overland transport. Large sailing ship can carry 900 tons of grain, with 600 tons for hulk-type ship and 300 tons for cog-type ship. Smaller ships used for riverine transport carry 20 to 30 tons.

Equipment carried by a soldier is generally 50-60% of body weight. Assuming 150 lbs average, this means 75 lbs of equipment. Full plate weights 40 – 60 lbs (18 – 27 kg) with 50 lbs average, while heavy infantry half-plate weights 15 – 25 lbs (7 – 11 kg), with 22 lbs average. Weapons weights are 5 lbs (poleaxe), 2,4 lbs (arming sword), 10 oz / 486 g (dagger); as such, total weight carried by an infantryman is 30 lbs / 13,6 kg. This leaves 45 lbs for food and other accessories.

Each troop detachment, depending on size, should have a person or group trained in medical treatment of wounds. A small body of men are detailed during the battle to take care of the wounded as well as to convey water to the front lines.

Post system includes regular rest stations (mansiones) and relay mounts for fast post, and oxcarts for slow post. Stations are at half-day's or full day's journey on foot.