So now we have our entire “campaign community” of men, women and animals. And so it might be worth doing some quick calculations to get a sense now of exactly what a community of this size is going to require. For a general sense of scale, we’ll consider the demands of a standard Roman army of the Middle Republic: two legions plus matching allied detachments, totaling around 19,200 soldiers (16,800 infantry, 2,400 cavalry).
Let’s deal with animals next. Each contubernium (“tent group”) of six soldiers likely had its own mule, so that’s 3,200 mules for the army, plus some additional number for the siege train and any army supplies; perhaps around 5,000 total (see Roth, op. cit. on this). On top of this we have horses for the cavalry; this will be rather more than 2,400 since spare horses will have been a necessity on campaign. Judging by Roman barley rations for cavalrymen (presumably intended to feed the horse) it seems a good guess that each cavalryman had one spare; for later medieval armies the number of spares would be substantially higher (at least three per rider). But for our lean army of Romans, that’s just 4,800 horses. An early modern army might require quite a few less mules (replacing them with wagons), but at the same time it is also probably hauling both field artillery and siege guns which demand a tremendous number of draft animals (mostly horses). My sense is that in the end this tends to leave the early modern army needing more animals overall.
Next the non-combatants. The mules will need drivers and the cavalrymen likely also have grooms to handle their horses, which suggests something like 3,400 calones [slaves or servants] as an absolute minimum simply to handle the animals. Roth (op. cit., 114) figures one non-combatant per four combatants in a Roman army, while Erdkamp (op. cit. 42) figures 1:5. Those figures would include not merely enslaved calones but also sutlers, slave-dealers, and women in the “campaign community”. Taking the lower estimate we might then figure something like 4,000 non-combatants for a “lean” Roman army, with many armies being more loaded up on non-combatants than even this. And while estimating the number of non-combatants for Roman armies is tricky, we actually have some figures for pre-modern armies to give a reference. Parker (op. cit. 252) notes units of the Army of Flanders (between 1577 and 1620) as high as 53% non-combatants, including women in the campaign community; one Walloon tercio in 1629 was 28% camp women on the march. It is tempting to compare these but caution is necessary here – both Roth’s and Erdkamp’s estimates are heavily informed by more modern armies so the argument would be circular: the estimates for the Romans look like later armies because later armies were used to calibrate estimates for the Romans.
That gives us an army now of 19,200 soldiers, 4,000 non-combatants, 5,000 mules and 4,800 horses. Roman rations were pretty ample and it seems likely that many of the calones did not eat so well but the ranges are fairly narrow; we can work with an average 1.25kg daily ration per person normally, with the absolute minimum being the 0.83kg daily grain ration following Polybius (Plb. 6.39.12-14, on this note Erdkamp op. cit. 33-42) if the army was short on supplies or needed to move fast eating only those buccelatum [hardtack] biscuits. That’s a normal consumption of 29,000kg per day for the humans, with the minimum restricted diet of 19,256kg for short periods. Then we need about 2.25kg of feed for each mule and about 4.5kg of feed for each horse (we’re assuming grazing and water are easily available), which adds up to 11,250kg for the mules and 21,600kg for the horses.
And at last we now have the scale of our problem: our lean army of 19,200 fighting men consumes an astounding 61,850kg (68.18 US tons) of food daily. It also consumes staggering amounts of water and firewood. In order to move this army or sustain it in place it is thus necessary to ensure a massive and relatively continuous supply of food to the army. Failure to do that will result in the army falling apart long before it comes anywhere close to the enemy.
Bret Devereaux, “Collections: Logistics, How Did They Do It, Part I: The Problem”, A Collection of Unmitigated Pedantry, 2022-07-15.
March 18, 2026
QotD: Feeding a Consular Roman army
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