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Assume that a pre-modern army numbering 50,000 men is going to campaign in a foreign territory for 180-days, during which they completely rely on their supply wagons which cannot be refilled, and each wagon is pulled by two oxen, how many oxcarts are needed supply all soldier?


My own research is probably way off, but I present it nonetheless:

First, we must determine how much food the army is going to need. According to this article Roman soldiers were given 1 pound of meat every day, while it doesn't seem to be all they got, we can use it as a baseline. Therefore:

total weight of food = 1 ld × 50,000 × 180 = 9 000 000 lds

Then we must determine how much can two oxen, according to this they can pull three times their own weight, according to Google average weight of an ox is around 2000 lds, thus.

pull weight of two oxen = 2000 lds × 3 × 2 = 12 000 lds

Then there is the cart itself and its driver. Estimating 1 0000 lds for cart weight seems fair, and driver's weight 200 lds, thus:

loading capacity of cart = 12 000 lds - (1 000 lds + 200 lds) = 10 800 lds

Which would mean that:

number of oxcarts needed = 9 000 000 lds / 10 800 = 833 oxcarts

That number seems unsurprisingly small...

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    $\begingroup$ The load of a cart seems about two times too large; I would expect more like 2 or 3 tonnes instead of 5 or 6... But you forgot the most important thing, namely the fodder for the oxen themselves, and for the horses. And you forgot the need to carry ammunition, tents, siege engines, spare equipment and other such things. The army is not going on a sightseeing trip, they are there to fight. (And the abbreviation for pound is lb, ell bee, from Latin libra, pound.) $\endgroup$
    – AlexP
    Oct 13, 2021 at 0:46
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    $\begingroup$ One pound of meat and nothing else will not keep a warrior alive, so double your starting requirements to account for some grain, poultry and other essentials. Then add cooks, ox drivers and assorted other support staff, increasing the number of mouths to feed substantially. Now on the positive side, once a cart is empty, you can eat its oxen. Also, not all meat has to be dead weight hauled along on carts. You can bring a herd with you for the small cost of a few herdsmen and their dogs. $\endgroup$ Oct 13, 2021 at 0:48
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    $\begingroup$ 800 carts would make a column about 16 kilometers (10 miles) long. Moving at about 3 km/h (2 mph), a reasonable speed for an ox-driven cart, that column would take 5 hours to pass in front of an observer. (Which is important because it limits the time they can travel in a day.) $\endgroup$
    – AlexP
    Oct 13, 2021 at 0:51
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    $\begingroup$ One should expect some spoilage in 180 days. $\endgroup$ Oct 13, 2021 at 0:54
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    $\begingroup$ Oxcart: The Conestoga Wagon was the culmination of oxcart technology, and popular in North America in the 18th and 19th centuries. It could haul 6 Tons = 12,000 lbs = 5400kg in dry, flat conditions. Much less through heavily rutted mud or off-road. Remember to pack plenty of feed for the draft animals, since yoked animals cannot forage, and that many cargoes will cube out before they reach maximum weight. $\endgroup$
    – user535733
    Oct 13, 2021 at 13:56

8 Answers 8

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I agree with the people who write it won't work, but with a slightly different emphasis.

  • The daily food allocation per soldier is almost irrelevant, but in addition to AcePL's figures for Roman soldiers, consider the humanitarian daily ration at 1.9 lbs. It provides 9,200 kilojoules, while MRE are some 5,000 kilojoules (three per day). So a soldier would need some 3 lbs. of HDR per day. Compared to the Roman figure, that's close enough for government work, but I'll go with those 3-4 lbs. to account for the lack of modern preservation -- there will be spoilage.
    50,000 people need about 100 short tons, slightly less than 100 metric tons per day.
  • I think you are grossly underestimating the weight of an oxcart. Googling a couple of sources gives about 500 to 700 kg for a roman wagon. That means 140 to 200 wagons per day.

Trick question, where do they come from?

  • A typical oxcart could do 2 mph for 5 hours per day (random googling).
  • The oxen will need food. They might graze (only 5 hours of travel per day), but they will also need supplemental food if they do heavy work. And the pastures along the road will be gone soon. 18 kg per day per oxen.
  • So for each day, the notional oxcart would consume 5% or more of the load.

After at most 20 days, all your food/fodder is gone feeding the oxen.

  • An oxcart could start out loaded half with cargo, half with fodder, and consume all that fodder within ten days (100 miles). That would leave you with an oxcart, the cargo, and no fodder for the return trip.
  • More reasonably, there are plenty of supply depots. Some oxcarts carry only cargo, others only fodder to various depots. The calculation gets slightly more complicated, especially if you turn some of the oxen into soup instead of returning empty carts.
  • Then there is the problem of assembling food at the starting camp. With luck, it is a (river?) port. If it is merely a fertile farming area, food/fodder will be required to collect the food.

You will need well-stocked supply depots in secure terrain close to your operational area, plus constant resupply. The alternative is looting, which devastates the area rather quickly. L.Dutch mentioned that. (I don't think canned food is the key development, I think it was more due to a state that could maintain enough granaries. But that's a detail.)

When I wrote that the daily ration almost doesn't matter for the calculation, it was for two reasons. First, oxen eat more than men. Second, if you have an organized state to provide 100 tons per day, a few percent more or less won't break it.

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  • $\begingroup$ Eat the oxen when they run out of fodder, smoke the meat, and have the soldiers pack it. $\endgroup$
    – Monty Wild
    Mar 12 at 9:14
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    $\begingroup$ @MontyWild, hey, oxen are expensive. This is supposed to run for half a year. $\endgroup$
    – o.m.
    Mar 12 at 10:47
  • $\begingroup$ Few things: 1. Romans knew about spoilage, that's why they chose food suitable for medium-to-long-term-storage. Olives, olive oil, flour/grain, fruit etc are good for several weeks to several months. Roman Legionare treated flour maggots like a part of the diet... Meat would be walking on it's own legs. 2. I forgot it myself, but walking meat and oxen for carts can be combined, as well as firewood and carts (though good cart is expensive). 3. You underestimate the max load of ROman heavy oxcart - it is 1500-2000 kg, though true - halving it extends lifespan. $\endgroup$
    – AcePL
    Jun 21 at 8:46
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More wagons than you can get.

Pre-modern armies on the march were generally limited to 40,000 or fewer men. Any larger force was either a temporary concentration for a battle, or was marching along a river, where barges could be used instead of wagons.

Beyond about 40,000 men, the supply wagons (and the supplies for the supply wagons -- draft animals need to eat, too) would crowd any road system to the point where food simply couldn't arrive at the army fast enough to keep it fed.

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In 1862 General Sibley invaded New Mexico with a Rebel army and pushed back the defenders under General Canby. At the Batle of Glorietta Pass, March 26-28, the Rebels defeated the main Union force. But a detachment under Major Chivington captured the Rebel supply wagons at Johnson's Ranch, killig or diring off 500 horses and mules, burning 80 wagons and their supplies, and spking the cannons.

The Rebel army retreated down the Rio Grande valley back to Texas

The Army of Northern Viginia had about 71,000 to 75,000 men at the start of the Battle of Gettysburg on July 1-3, 1863, and several thousand fewer men at the end of the Battle. Lee began to retreat on the evening of July 4. The supply wagons carrying supplies and thousands of wounded men were escorted by cavalry under general Imboden. And I have read that the wagon train was 17 miles long, which would be about 89,700 feet.

And if the Union had managed to capture those hundeds or thousands of wagons, the Army of Northern Viginia would have been unable to operate until the wagons and draft animals were replaced - if they could be replaced.

The Army of the Cumberland was defeated by Rebel forces at the Battle of Chickamauga on September 18-20, 1863, and retreated to Chattanooga. There were tens of thousands of soldiers in the Army of the Cumberland and they needed a lot of supplies.

Wheeler and his troopers guarded the army's left flank at Chickamauga in September 1863, and after the routed Union Army collected in Chattanooga, Gen. Bragg sent Wheeler's men into central Tennessee to destroy railroads and Federal supply lines in a major raid. On October 2 his raid at Anderson's Cross Roads (also known as Powell's Crossroads) destroyed more than 700 Union supply wagons, tightening the Confederates siege on Chattanooga.

So more than 700 Union supply wagons were destroyed at Anderson's Cross Roads on October 2, yet that was not enough interruption in supply to starve the Army of the Cumberland into giving up Chattanooga. There should have been hundreds or thousands of other wagons making supply runs to and from Chattanooga in different convoys.

So I think that your estimate of 800 oxcarts, which would probably be smaller than the Civil War era wagons, to supply 50,000 men is an underestimate. And they might make several supply runs (heavily guarded, of course) to and from the army in the field during the 180 day campaign, instead of remaining with that army for the entire campaign.

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In Roman legion, food allotment for a legionare was 2-3 pounds of grains (or flour) and 1 pound of meat and other foodstuffs like Olive, fruit, wine etc. Generally 75-80% grains, 20-25% meat and other components. So you immediately need to quadruple your calculation.

Also, while food was calculated per head, it was distributed by squads. That means that once a week squad leader would go to the quartermaster and receive 1 week of food for 8 people. Then food would be prepared on the fire - meat would be cooked into soup or on open fire. It would not last a week, but after that it would be supplanted with olive, fruit etc, all as addition to porridge or bread or - especially during marches - hardtack. Hardtack needs to be baked, twice at least, for several hours each (preferably more), which requires a lot of firewood. That firewood also needs to be in allotment.

To save on transport space I'd change flour or grains (which soldiers would often ground themselves) to hardtack from the start, as it's easier to transport and it's "condensed". In that case 1 lb of hardtack would be a daily allotment - which reduces the total daily ration by 50%. So, 2 pounds - 1 kilogram - of food (tack, meat, olive oil, wine, vinegar, fruit) would be about right.

As others mentioned, you forgot the other things: food for scout cavalry (horses, depending on unit it would be at least 600), food for oxen, but also Roman legion on the march didn't carry all equipment on the legionare's back. Tents, armor, weapons, ammo for projectile weapons, spares, kitchen utensils, digging tools (to build fortifications for the night, every night), heavy weapons (scorpions, onagers etc, disassembled), fuel for fires (if unavailable on campaing terrain), emergency water rations... This was transported in the baggage train.

Jonathan P. Roth in his book THE LOGISTICS OF THE ROMAN ARMY AT WAR (264 B.C. - A.D. 235) gives the breakdown of nutrition standard and quantities that were required to feed a Roman legionare. In short, it boils down to about 6000kg of food per day. Multiply it by factor of 10 (nominal strength of legion after Aurelian reform is 4800, if double-sized First Cohort then 5200) and for 180 days it's 11k tons of foodstuffs total.

50000 legionares on 180 days of campaign, having their own food for whole campaign with them? Impossible. Baggage train (which was actually mostly mules, with one or two per squad, with only some carts for really big and heavy loads) would be so huge to be be unmanageable - 10k-12k mules carrying squad's equipment alone is a staggering number, let alone added 5.5k ox carts each carrying 2000kg. And this cart max load is a technological limitation; heavy oxen cart would be heavy, made from oak and iron, weighing 1500kg - 2000kg. Thus, 140mm-diameter-double-axed oak cart has per-axle load limit of 1500kg, making it's gross weight no more than 3500kg (subtract 125kg per wheel; they do not count towards axle-load). Then there's food for mules and oxen, food for slaughter animals... food for oxen for more carts...

Even if moving along rivers, the supply chain must be steady and secured. So quickly force would become smaller, with a lot of detachments to cover supply trains (road or water)...

However. Depending on the region chosen for the concentration before moving to war and how long the expedition will be within it's borders, the baggage train is much smaller, as food can be "delivered" to the places where force will make camps for night.

Then every day the baggage train will be smaller, because you can use oxen for meat - and they will be slaughtered when needed, and in the meantime you can use them as spares, then effectively doubling the daily mileage (at some point, initially it will be as slow as one expect).

You could alleviate a lot of those issues if you choose a objective relatively close to your borders and you make it a defensive, fortified position, thereby allowing for reduction of the daily ration by anything between 25%-50%. Combined with combat losses you could get away with halving the baggage train, which sounds impressive, but going from 8000 carts and 10000 mules to 4000 carts and 5000 mules does not help much...

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Many have pointed out the basic logistics in detail, and why it's difficult if not impossible to get all that food for 50,000 fighting men (and cavalry horses, and oxen, and blacksmiths and tailors and cooks and laundry-workers, etc). However, I think people only skimmed over one aspect of why your campaign would fall apart: 180 days is twice the length of an average preindustrial campaign. As noted in several answers, most preindustrial campaigns took place in summer because that was after the main spring planting and before the next harvest.

The biggest reason a smart person doesn't want 50,000 men in their army during preindustrial times is because most of those people would be farmers, NOT professional soldiers, so you need to send them back home to harvest the crops.

At least, you SHOULD send them back home, if you don't want your country plunging into a famine. And depending on how big your country even IS to field 50,000 fighting men, both population-wise and geography-wise (England? France? How EASILY can this place let 50,000 men and however many logistics-people take away a huge amount of food, head off to enemy territory, and basically stop contributing to society for the next few months?), the three-month campaign would probably have EVEN LESS realistic time at full strength--you can't just mark off the days until the campaign's OFFICIALLY at Day 180 and let them go home.

You have to let your men recover from injuries or illness, and then give them enough time to get home AT the harvest. Unless they live right at the two countries' border and it's only a day or two away, most of these soldiers would be infantry, and they'd be walking back home. How far is it--a week? A month?

Most importantly, how hostile is enemy territory? Why do they even need 50,000 men, and why are they away for half a year? There needs to be a really important reason for your scenario, especially with all the difficulties that made it so hard in real life.

If I was a preindustrial woman--especially one of those many farmers' relatives--and if my son/brother/cousin was sent to bulk up a massive, damn-near-impossible 50,000 man army, I would be terrified of two scenarios:

  1. This is a suicide mission for about half the army. And unless I'm a protagonist, I'm pretty sure my relatives are in the half that's not coming home.

  2. The enemy is heading for us, and nobody cares about food right now because they need every able-bodied man they can get to slow them down.

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  • $\begingroup$ Why do you presume the majority of the soldiers would be rural conscripts? What part would exclude them from being standing army or mercenaries? $\endgroup$
    – Chlodio
    Mar 13 at 15:21
  • $\begingroup$ Just think about all the logistics that everyone already said was RIDICULOUSLY hard for preindustrial societies, and then figure out how much harder it is with PROFESSIONALS, especially if you want them on any kind of short notice. Where are all these professional soldiers and mercenaries coming from? How much payment would they need--50,000 silver coins a month? 100k? Would they get paid in GOLD, gods forbid? Trying to field a professional and well-equipped army this size would bankrupt a lot of monarchs once the OP's double-length campaign is finished. $\endgroup$
    – Jamie L.
    Mar 13 at 16:54
  • $\begingroup$ Romans partially figured all those issues out. Soldiers were farmers by birth, but most were also volunteers. On campaign they will be paid once every half-a-year, and of course casualties were paid to the families, thus no need to carry coin for them. So no, most campaings (including modern one, like Barbarossa in 1941) were in summer simply because it was dry, warm season making for good roads. (of which most were dirt tracts, only sometimes "reinforced" with wood - those would be highways). Also, army could forage at this time, especially on expedition. $\endgroup$
    – AcePL
    Jun 21 at 9:06
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    $\begingroup$ @JamieL. Yeah, I was imprecise as well. So. You're right - That big army marching is visible from far. So by the time soldiers are near any village it is long emplpty. Soldiers foraging aren't much different than tax farmers sent by their lord. Same difference. Farmers will not retaliate anyway, because it's not worth it. Remember, back in those days wars are much more frequent - say they will fight off foragers this time, but in a few years (or next day) those soldiers will come back and they will not shrug hands when finding empty village - they will raze it: burn, pillage, sow salt etc... $\endgroup$
    – AcePL
    Jun 22 at 19:01
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    $\begingroup$ @JamieL. Like i said: life back then was hard, especially for poor folk. Those were ultimate pragmatists: better to lose pig than head; they have family to feed and hard farm life was dangerous enough. it's not like simple wound today- back then ANY wound could be fatal, differenxe was in how long will take you to die... So farmers would simply... disappear them and their families and food and worthy possesions. In fact, they will have that planned for a long time. $\endgroup$
    – AcePL
    Jun 22 at 19:08
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Don't Forget Fodder and Equipment

Quick fact check shows the average working horse requires aprox 1.5 to 2 kilos of fodder or grain for every 100 kilos of body weight.

So just to make things more difficult all your horses, pack animals and oxen etc are going to add to the complexity of your logistics operation. If there's insufficient natural fodder available for all of your animals you actually have to start hauling animal feed by wagon as well.

PLUS

Short and in no way complete checklist;

  • Tents and rope
  • entrenching tools (picks and shovels)
  • forges & blacksmithing equipment, coal for same and spare feed stock for forging
  • building tools (saws, hammers, nils etc)
  • camp furniture (for officers & admin staff) plus paper, ink quills etc
  • parts for seige equipment or field artillery & ammunition for same
  • barrels of oil for cooking and lighting, water barrels, bags of salt
  • spare munitions, arrows, spears, sling shot
  • etc
  • etc
  • etc
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Making such estimate is almost pointless, raiding the territories is "best by test", to quote Bobby Fisher.

There must be a reason why all armies until the invention of canned food relied on raiding the territories where they were waging wars for supplies, and in particular the roman army only went to war in summer, and that's precisely because if you want to be self sufficient in a war in those times, your only option is to not go to war.

You need a properly established supply chain, a properly established transportation network infrastructure, a reliable way of transporting and storing the supplies, and you need all of that to be safe from the enemy's interference. There must be a reason why still today railways, harbors, bridges and highways are among the primary targets in a war!

If you have a little group of soldiers out on a mission of few days they can bring supplies with them. Increase either of the two numbers, and you have to rely on what you find on site.

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  • $\begingroup$ That's not entirely correct. Long sieges relied on solid supply lines for the besieger even in hostile land for example the SIege of Masada. $\endgroup$ Oct 13, 2021 at 6:43
  • $\begingroup$ @TheShadowOfZama, true, but that was a way to break the siege: break the supply lines, and see who starves first. $\endgroup$
    – L.Dutch
    Oct 13, 2021 at 6:46
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    $\begingroup$ "all armies until the invention of canned food relied on raiding the territories", are you sure about that? I was under the impression that at least Hellenic armies of antiquity relied heavily on supply wagons, and we have accounts of these supply wagons being captured and completely ruining the campaign. I also believe that while supply wagons fell out favor during the medieval period, they were brought back during early modern period, and Napoleon on the other hand revived living-off-the-land practice. $\endgroup$
    – Chlodio
    Oct 13, 2021 at 11:37
  • $\begingroup$ @Chlodio The captured wagon trains mentioned in some battles of Hellenistic period were not for supplies, those were possessions of the soldiers. Loot from years of campaigning, wifes and children, this sort of things that you can't pack onto mules. In fact most efficient method for carrying supplies were the troops themselves, and that is how majority of good ancient armies solved the problem if there was a problem with supplied on the way. But in general living off the land was name of the game till railroads appeared. $\endgroup$
    – Archelaos
    Oct 13, 2021 at 17:39
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IMO your computation is missing important point

First, your computation does not consider food consumption for the oxen. If you want them to work, they have to be well-fed and given rich nutriment. interesting link on how to take care of oxen

Depending on the quality of supplement, it is 2.5 kg (5.5 lb) to 6 kg (13.2 lb) per day of food given to the oxen. That is assuming they are grass in the land you are visiting else you need hay (hay per cows) as in average they consume around 24 pound per days of dry food.

Second, IMO your estimate is overly generous. It is true that oxen can pull, 10000lbs, but it is for short sprint like distance link. For days long walking, you are looking at around they own weight. So it more of 2000 per oxen and 4000lbs per pairs.

So, a rough estimate on how long they can sustain themselves.

4000 / 11 = 363 days

4000 / 26.4 = 153 days

4000 / 48 = 80 days

Now taking that into account, your equation actually becomes more complicated are your food supply are consumed by your soldier (that IMO you under evaluate) but also your oxen, and you require more oxen to feed your oxen. See where we are going there? Furthermore, as others have pointed out, you also likely need to transport equipment.

Moreover, we do not talk yet about speed, but your soldier would outpace oxen as in average an ox can do 15 miles (ca. 24 km) a day.

I will stand with other answers and tell you that such logistic in preindustrial time is not sustainable.

For such operation, you need either to follow a river or a coast and have boat-based logistic with large supply depot or rely on the land you are in either foraging or commerce.

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