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The average horse eats 10-20 pounds per day, according to this pet website. Considering the fact that the horses may have to eat even more because of the hard traveling they had to endure, it's likely that food costs must have been incredible. Genghis Khan's army traveled an average of 14 miles (23 km) a day during the China campaigns, with some claiming they traveled 120 miles per day when 'charging towards a target'. In addition, each horseman kept 3-4 horses in tow.

What really mystifies me is that he managed to conquer the Khwarazmian empire with 80,000 to 100,000 mounted archers, even though it was situated in Eastern Iran, a dry and arid desert!

Pieter Geerkens
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Twilight Sparkle
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    "Genghis Khan's army traveled up to 100 miles per day (160 km)": I would very much like to see a source for that claim. – Eugene Seidel Sep 30 '13 at 12:04
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    I actually got that from Wikipedia, which didn't cite its sources. I've checked via Google Scholar, and incorporated additional sources into the question. – Twilight Sparkle Sep 30 '13 at 14:46
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    Is it possible that their horses were 'low maintenance'? Certainly Khan's men were not your 'average man on the street' of today - they were something else entirely. Perhaps this is also applicable to their horses? –  Oct 01 '13 at 02:34
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    I want to note that all Mongols were herders. They know horses more than anyone at the time. Also some sources say "Mongols army goes like thread, it takes weeks to reach from start to end". It's unlike European army which marches in big large group, so those calculations will not simply apply to Mongols. – Melug Mar 04 '14 at 07:59
  • Hello Melug, welcome to History Stack Exchange! I notice that you're from Mongolia! I'm a little curious about your comment: Do you mind explaining what difference moving like a thread vs moving in large groups would have on the amount the horses would need to eat?

    Please feel free to leave an answer if you have any other insights!

     – Twilight Sparkle Mar 04 '14 at 14:15
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    @TwilightSparkle : it's a bit like physics...spreading the consumer load (horses) over time (<dt) still requires the same amount of energy (amout of forage) but decreases the required amount of power (amount of forage per time) thus having a much lower impact on the territory – Matthaeus Sep 11 '14 at 11:05
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    In other words: while spreading your forces might not be a good tactical choice, it's a good logistical one. It makes sure your forces don't exceed the local supply limit and gives the land a chance to recover and feed the rest of your army. – Matthaeus Sep 11 '14 at 11:11

6 Answers6

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Let's do the math: 100,000 mounted archers * 4 horses each * 10 kg/day * 250 days/campaign = 1,000,000,000 kg of forage required each campaign.

As noted here annual forage yield of meadow steppe is about 2000 kg/ha; of typical steppe about 900 kg/ha; and even desert steppe yields 200 kg/ha. Thus the area required to support Genghis's cavalry for a campaign ranges between 500,000 to 1,000,000 ha, or 5,000 to 10,000 km^2. A single day's forage could be found in an area of 20 to 40 km^2, which seems quite a reasonable campground size for an army of 100,000 cavalrymen.

Of course, given this forage requirement, it is no surprise that Genghis's army moved so rapidly - if it didn't it was going to starve.
;-)

Update: Genghis's army rode ponies, not full horses, reducing forage needs accordingly.

Update 2:
Let me rephrase - The Mongols (and other steppe peoples such as Manchus and Turks) rode breeds of horse that average a bit under the modern 14 hands height limit for a pony. Let's say typically 13 to 15 hands. This is about one hand shorter than the height of a typical riding horse, of 14 to 16 hands. As fuel requirement generally goes as the cube of height, ceteris paribus, a horse/pony only 14/15 as high would require about 20% less feed. Make it 15% less to allow for cooler temperatures and a consequently faster metabolism for the breed.

Pieter Geerkens
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    Note that Genghis Khan's army consisted not ponies but smaller sized normal horses. These nomadic horses widely used by other people from central asia. For example Hungarians used "Hucul" horses - similar to mongolian horses -, their size are 15-20 cms shorter than european and arabic horses. Ponies in Genghis Khan's army was restricted to message purposes. – CsBalazsHungary Sep 30 '13 at 07:16
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    Additional fact about these horses were less needy, they eat vitrually everything, and they are lot more endurable than european horses. Setback of these horses were lower speed. – CsBalazsHungary Sep 30 '13 at 07:19
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    Its good to get the horse breed correct. However, its fairly reasonable to assume the amount of food consumed by an equid is roughly proportional to its size, so the point is still good. – T.E.D. Sep 30 '13 at 13:37
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    @CsBalazsHungary: In English at least, pony denotes a small horse, which may or may not be from one of the distinct "pony" breeds to which you refer. – Pieter Geerkens Sep 30 '13 at 21:26
  • +1 for "doing the math". But question: The horses would have to spread out over that entire territory to forage and find sufficient food and eat it. That would take considerable time. If so, wouldn't they have have to move on before eating enough? –  Oct 01 '13 at 02:30
  • @Vector: It's called grazing, and like other herd animals, horses evolved to do it efficiently. – Pieter Geerkens Oct 01 '13 at 03:38
  • @PieterGeerkens - I can accept that. But since you've done all this wonderful math for us, don't you need to take into account the grazing rate to complete the answer? Without that, my question seems glaring: If they have to travel a certain distance within a certain amount of time, the grazing rate required for adequate nutrition has to support that, or your numbers won't work. –  Oct 01 '13 at 04:28
  • @Vector: Personally I think that Pieter's analysis is very solid. His conclusion that they would need 40km^2 pasture per day is even supported by other textual sources (in spyder's fascinating post) which is really impressive. He ignored the grazing rate probably because it isn't material: A horse walks at 4mph meaning that a journey of 20 miles would take 5 hrs. This leaves 19 hrs for grazing which is more than sufficient by 4 to 8 hrs. – Twilight Sparkle Oct 01 '13 at 08:13
  • @TwilightSparkle - that's fine with me. I upvoted Pieter's answer - I also think it's very good. Still, I don't know that much about horses and I do know something about numbers, and so I like it when Pieter does math... :-) Be that as it may, now you have done the math, so all's well. –  Oct 01 '13 at 08:18
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    @Vector: All working horses, from thoroughbreds to cart pullers, survive quite comfortably on eating done after several hours of work each day. BTW The working gait of a horse is it's trot (except for a few breeds where it is the faster canter), of about 10-12 mph. This is the gait at which Genghis' cavalry would have marched. – Pieter Geerkens Oct 01 '13 at 11:14
  • @PieterGeerkens: OK, that's a horse of a different color... now I understand. :-) –  Oct 01 '13 at 17:06
  • I wrote the note on pony, because the official difference on pony and horse is a solid height limit, and these horses are vary between ponies and horses, so some of them are below these limits, some of them are over it. So this definition of ponies are hard to apply on them. We can't really say that very same breed of these horses are ponies some of them are horses. Altogether the answer is good. – CsBalazsHungary Oct 02 '13 at 08:45
  • @CsBalazsHungary: Let me rephrase - The Mongols (and other steppe peoples such as Manchus and Turks) rode breeds of horse that average a bit under the modern 14 hands height limit for a pony. Let's say typically 13 to 15 hands. This is about one hand shorter than the height of a typical riding horse, of 14 to 16 hands. As fuel requirement generally goes as the cube of height, ceteris paribus, a horse/pony only 14/15 as high would require about 20% less feed. Make it 15% less to allow for cooler temperatures and a consequently faster metabolism for the breed. – Pieter Geerkens Oct 19 '13 at 12:34
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    My wife owned and rode a Mongolian horse when she lived in Siberia. They are short and hardy creatures. – called2voyage Dec 04 '13 at 16:06
  • 40 km^2 is a huge area and not at all a reasonable size for a campground. You could argue that it's reasonable as a forage area if they broke it up into multiple sites, but that is an insanely large area for a campground. And they would need a new one every day. – RBarryYoung Aug 01 '17 at 14:13
  • @RBarryYoung: IF you consider an army of 100,000 as being 200 battalions of ~500 men who camp and campaign together, then each such battalion would be setting up camp and a grazing paddock each day on an area ranging from 0.1 to 0.2 km^2. The dimensions of such an area would be 500 m by something between 200m and 400m. – Pieter Geerkens Aug 01 '17 at 20:51
  • So how would these 200 battalions be transporting and setting up almost 2 km of fencing every day? I understand the numbers, they just raise more questions than they answer. Especially if they were actually engaged, then they would somehow have to fight and at the same time find a new grazing area and setup the fencing every day. This doesn't so much answer the question as it highlights the real logistical difficulties of what the mongols were doing. – RBarryYoung Aug 02 '17 at 16:45
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    @RBarryYoung: I know this is an old comment, but horses can be hobbled or tied to a peg with a sufficiently long rope if you want to let them graze without them walking away too much. That is how it is done in Mongolia nowadays and I don't think this would have been hard to figure out 800 years ago. – Jan Feb 21 '20 at 21:08
  • @Jan I think that this is a good answer to the fencing problem, but it’s only one aspect of the immense logistical problem. I think that there must be an remarkable story behind this because finding and organizing that much grazing for that many horses every night would’ve required a lot of planning and coordination. – RBarryYoung Feb 23 '20 at 23:08
  • @RBarryYoung: The steppe is > 90-95% pasture - it's almost the definition of steppe. – Pieter Geerkens Feb 24 '20 at 00:59
  • @PieterGeerkens most of the wars were not in the steppes. If the Mongols had stayed in their steppes, we wouldn’t be talking about them now. – RBarryYoung Feb 24 '20 at 02:19
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This is not really an answer to your question, but the following numbers look much more realistic.

In the Russian army at the beginning of XX century daily ration for horses consisted of 4 kg of oats, 4 kg of hay and 1.6 kg of straw. Since the Mongol horses didn't eat oats (nomads had no oats) ration should be counted as hay - 15 pounds (6 kg) of hay per day per horse, or 1 800 tons of hay for the whole the Mongol army. If we assume that there were minimum 2 cows in farm household, this is year supplies of 611 courtyards, or about 200 villages. And when you consider that in January, when the Mongols has moved across Rus', half of the feed stock has been eaten by cattle. It is necessary to take into consideration guerrilla war and Mongolian robberies that spoiled much of the forage. It would not be an exaggeration that for for one day Mongols needs supplies of about 1 500 courtyards.

According to archaeologists, in the XIII century 1 courtyard handles 8 hectares of land per year, ie, 1500 courtyards handles about 120 square kilometers of arable land. Arable land could not be more than 10% of all lands. Hence Mongol horde had to move every day about 40 km, and send on both sides of the route groups of foragers for 15 km. But the speed of the horde in Rus' is known, Russian historian Ivanin tells that speed was 15 km per day. Thus, a number that tells the historian Kargalov - 140 000 warriors with 300 000 horses - is unrealistic. It is easy to calculate that at a speed of 15 km per day could move the army which had only about 110 000 horses.

According to Dmitriy Chernyshevsky, Zhaksylyk Sabitov ("Questions of History and Archaeology of Western Kazakhstan")

spyder
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Of course "thread" will cover much more area than "group". That means more steppe to feed horses. Let's say length of the army is 50km, and horses can go 2 km at most from the line to eat. Then it would cover 100km^2, and if army marches 23km a day, it would be 46km^2. Still sufficient. On the other hand, if they move in a dense group like rectangular then horse feeding is going to be problem as there are too many horses in less space. Also sparse much bigger rectangular group may lead to too much dust and soil devastation. So marching like "thread" is enforcement. Genghis Khan's army was full of cavalries. If there was more infantry like other nations, horses won't have problem of feeding in rectangular group.

Also Mongolian horse is kind of wild, it doesn't require much care like other horses(http://en.wikipedia.org/wiki/Mongolian_horse).

In Vasily Yan's "Bat khan" book, the army's maneuver explained in detail. Bat is grandson of Genghis Khan, apprentice of general Subotai. You may use the book as starting point to further investigation. Here's the google search results http://bit.ly/NSGCTt, book on Amazon http://amzn.to/1fFTiJD

I written quiet long post that doesn't fit in comment section, so dropped in answers.

Melug
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http://news.nationalgeographic.com/news/2014/03/140310-genghis-khan-mongols-mongolia-climate-change/

Between 1211 and 1225—a period that neatly coincides with the rise of Genghis Khan and the Mongol empire—central Mongolia enjoyed a spell of sustained benign weather unlike anything the region has experienced during at least the past 1,100 years and probably much longer.

The long run of unusually good conditions meant abundant grasses and a huge increase in herds of livestock and war horses that became the basis of Mongol power—a marked contrast to the long and exceptionally severe droughts that gripped the region during the 1180s and 1190s, causing unrest and division.

anon
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Other answers are right, but I'd like to add that an invading army horses don't just eat grass: they can also eat the crops that otherwise would have feed the invaded human population. That is, an invading army can feed its horses on wheat or barley on invaded land. A consequence of that is that the invaded population is likely to starve for a year, but that is not expected to be the main concern of the invading army.

In addition, grass yields from other answer assume the annual yield of steppe, but the annual yield of an steppe is not likely to be in the field at any given time because pastures are grazed year round - or at least in the favorable season. However, cereal fields are recollected once a year and therefore if the attack is properly timed invaders do have the complete annual yield at their disposal.

Pere
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  • Areas that do not have good access to surface water are grazed much less than areas that do. I do not know about the 13th century, but in modern times, pastures at higher altitudes are not grazed much except in summer, and those at lower altitudes are supposed to recover a bit in the summer months. So grazing is not uniform either. – Jan Feb 21 '20 at 20:59
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These Mongol horses of the steppe, early domesticates, tarpans, really, also provided milk for the cavalrymen, requiring significant added forage for lactation nutrition demands, which are quite high, given the high nutritional value of the milk.

Milk mares likely were not ridden, and there must have been foals, or perhaps the foals were weaned early (most can survive readily without nursing after a month of age), or eaten. The lactating mares continued lactating due to thrice daily milking, drank readily by the horsemen. Lactation can persist through the year, provided nutrition is adequate, lots of water, salt, and forage required.

As noted, these horse people knew grass, and where the best horse milk grass grew. The steppe grass nourished the horses, year round, it seems, and the grass-nourished horses fed the humans milk and meat in addition to providing transport. Campaigns must have been seasonal, so seasonal is the horse. When the grass is in season, conquest with horses is in season. The longest days provided the longest travel, shorter days, not so much conquest.

https://sidgustafson.blogspot.com Equine Behavior

Steve Bird
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