New Acquisitions: How Fast Do Armies Move?

This post is now available in audio format here.

Hey guys, this is just a really quick post to address a question I’ve seen lurking around thinking about my previous post on the logistics of the loot-train battle. No pictures today, just some quick text on the topic. A lot of readers were throwing up question-marks on how I was figuring marching speeds. I realized that I was taking for granted what would be understood in my field – the standard rule-of-thumb marching speeds.

A lot of readers questioned two things: first that Cersei reports riding from somewhere (King’s Landing?) to Winterfell in “a month” being discordant with the long march time from Highgarden to King’s Landing and second that 12-miles-a-day was much too slow. Both of these get into “how do we calculate how fast an army can move?” Let’s start with infantry on the march.

Infantry on the March

The intuitive and a touch clever method is to take normal human walking speed – around 3mph – multiply it by walking hours per day (maybe 8) and go with that. This makes intuitive sense, but if large army logistics made intuitive sense, they wouldn’t be hard, and as Clausewitz says (drink!) “War is very simple, but the simplest thing is very hard.” Logistics is very hard. So why don’t armies move at c. 25 miles per day?

So let’s think about – in very general terms – what needs to happen and in what order for a large body of infantry to march. Everyone wakes up and starts to get moving (probably around 5am). Breakfast need to happen, which may require making fires. Tents need to be struck and stowed along with all of the gear in the baggage train and individual soldiers need to stow their own equipment. All sorts of small tasks add up to eat away parts of the morning. Then everyone needs to get gathered and ready to march.

And now – because you are a large body of infantry, you wait. Let me explain – let’s take a nominally full strength (c. 3,000 men) American civil war brigade, marching on a road 13ft or so wide. You can get five men (a little cramped) into a single row on that road, meaning that the infantry itself stretches 600 ranks deep. Unlike in the movies (which love ultra-compact marching formations because it looks cool) you need a few feet of seperation between rows for best effect (WW2 US Army guidelines specified 2-5 yards), let’s assume each soldier occupies about 5 feet in the marching order. So the infantry is 3,000ft long (914m; nine football fields). We also need unit separation (between the regiments, it’s important to avoid ‘accordioning’ on the march and facilitate control; WW2 army regs suggested 100 yards between companies, 50 yards between platoons, so these could be quite large), so let’s round up to 4,000 ft (1219m; 13 football fields).

But we also have tents, food supplies, spare ammunition and all sorts of other of what the Romans would have called impedimenta (sidenote: if you are thinking, “well, but a pre-gunpowder army doesn’t need this; 1) arrows take up space and 2) camp entrenching supplies – the Romans marched heavy). How many wagons, pack animals or porters you need varies – the Romans seem to have often moved with a mule for every six-to-eight men, plus the army’s siege train. A good rule-of-thumb I’ve seen for American Civil War estimates is around 20 wagons per thousand, so 60 wagons. Rule of thumb in the ACW is 80 wagons to a mile of road, so our wagon train ought to take up around another 4,000ft.

(Sidenote: you can see why logistics gets complicated fast. Even in explaining a rule of thumb, I have to resort to rules of thumb, or else we have to inventory all of the stuff an infantry brigade needs, and all of the food they need and then parcel it out by wagons (and then figure for the mule-or-horse teams for the wagons) and on and on. Fortunately for the historians, this sort of work was done by the armies at the time and written down, so we tend to use their staff-work.)

So the entire force is probably a bit more than 8,000 ft long – 1.5 miles. In practice, there’s actually a lot more space eaten up in separation (between wagons, between men) so it would be longer, but I don’t want to get lost in the details. And this is for just 3,000 infantry – we have no cavalry with their many spare horses (three per man as a typical minimum) or god forbid a siege train which might involve hundreds of wagons.

Here’s the thing: the last man in the line cannot start marching until that entire formation has marched past him. The more men you are sending down the same road, the worse the problem gets. For our single brigade, the wait is probably close to an hour. For an army of – say – 10,000 men, you’re now talking about the last man waiting in the camp while some five miles of army marches past him (that’s about 2-3 hours of waiting). Moreover, the front of the army has to stop where the last man will stop for the night (since the army camps together, because to do otherwise is dangerous). And remember, that last man may have started marching hours after the first man, putting him miles back down the road. So another two or three hours where now the front of the army isn’t moving even though the back is. And worse yet – the entire army is limited to the speed of its slowest element – either waiting for it to move forward in the morning or waiting for it to catch up in the evening.

Well, getting started ate quite a few hours, but at least we’re going to move at a constant speed all day right? Of course not. These are humans – they need to eat (lunch), drink and relieve themselves. Men will fall out of line because they are sick or because they sprained an ankle or because they’re tired of marching and faking it (many army guidelines put the medics at the back of the marching column for this purpose). To add to this, wagons get stuck in the mud, mules and horses get stubborn or lame (that chance may seem low, but remember we’re dealing with thousands of animals – small percentages add up fast when you have a few thousand of something).

For reference on how much time this can eat up, 1950s US Army marching regulations (this is again FM21-18 “Foot Marches”) suggest that “battle groups or smaller” (800 men or less, generally – so small, fast-moving infantry) can “under favorable conditions” (read: good, modern paved roads in good weather) make 15-20 miles in a continuous eight hour march. A forced march – marching longer than 8 hours and at a higher than normal pace – can cover more ground (c. 35 miles in a day in some cases) but such a pace will wear out an infantry force fast.

At the end of the day, the army needs to arrive at its planned camp site long enough to make camp. Cooking needs to be done. Food that was foraged by flanking units needs to get to the camp, be recorded and stored (or processed and eaten) – speaking of which, note that we haven’t even discussed flankers, scouts and foraging parties. Wages may need to be paid, paperwork needs to be done. In many armies, the camp will need to be fortified – the Romans built a wood-palisade fortified camp every night on the march. And then everyone goes to sleep around 9pm. And that, to be clear, is when everything works like clockwork – which it never does.

For a large army, the breaking camp, waiting to begin marching, waiting for the last man to arrive, dealing with pack animals and wagons slices a few hours off of that eight hour march routine. All of which is why a normal large body of infantry moves something closer 8-12 miles per day than the 24 miles (8 hours x 3.1mph) per day implied by Wikipedia’s Average Human Walking Speed.

Historians doing studies of campaigns thus tend to use these sorts of rule-of-thumb speeds without much feeling the need to explain why armies move so slow because I think they expect that most of their readers are either fellow historians or former soldiers and in either case, already know. These rules of thumb, in turn, derive from staff planning in the age when armies still mostly walked to war (especially the 1800s and early 1900s): those staff office planners would have (and presumably still do have) elaborate tables of how many men can move how fast over what sort of roads in what kind of weather – because bad staff work multiplied over massive armies can mean catastrophic logistics and timing failures (see: Frontiers, Battle of the (1914) for examples).

If anything, for a medieval army of conscripts, fresh from a successful battle, with a long supply-train moving off of the main roads, 12 miles per day is actually quite fast. Large armies with lots of wagons often strayed into single-digit marching speeds. And, to be clear, marching speeds are highly variable based on terrain and the rest. For Jamie straying off the Roseroad, terrain would be deeply unfavorable for his wagons, slowing him down further.

Getting to Winterfell on Horseback

Ok, and what about Robert’s royal progression making it to Winterfell in “about a month?”

According to the standard reckonings, Winterfell is 1,600 miles from King’s Landing (this is based on using the official maps and creating a scale from the known length (100 leagues = 300 miles) of the Wall), but we actually don’t have any dialogue suggesting that the Royal Party went directly from King’s Landing to Winterfell – it’s possible the ride was shorter (sidenote: these kinds of travel distances are part of why the sort of kingdom Robert has – where rule requires personal relationships like this – doesn’t get this big historically).

Robert’s party may be large by our standards – a few hundred individuals, all mounted – but by army standards, it’s a tiny force. And small groups of cavalry, if they ride hard and bring spare horses (and they do) can move very fast. As I’ve noted before, the Mongols manage strategic movements over long periods up to 60 miles per day, but then, they are the Mongols. And the books note specifically that the pace was unlikely to be too rushed, since Robert had brought his entire family.

There are a lot of things we could do to make this work. If we had Robert ride quite hard, he can make it in maybe 35 or 40 days, which we might say is “about a month.” We might also have Robert start from somewhere further North (perhaps Darry or the Eyrie or even the Twins), since the sort of personal kingship that Martin seems to have envisaged (but not always planned for) historically required very frequent travel.

But I think all of that is over-complicating the obvious, which is that – taking much of the worldbuilding of Westeros together – it is clear that while Martin is great at many things, managing scale in his world is not one of them. I realize that one of the claims that ASoIaF fans like to make for their series is that it is ‘more grounded’ and ‘more real’ than other medieval fantasy (Martin occasionally makes this claim too), but speaking as a specialist in pre-modern armies and economies (particularly Roman ones), it isn’t. In practice, then, I think the mostly likely thing is: the story-teller messed up and misjudged the time it would take to cover the distance.

(A word: if anything, Tolkien’s first-person experience of war and his deep grounding in medieval and Anglo-Saxon literature means that – while Tolkien does not stop to discuss Aragorn’s tax policy – Middle Earth tends to fit within the ‘zone of the possible’ much more neatly than Westeros. Armies in Middle Earth move at normal speeds, the economic and population systems (and the human terrain with them) make sense, characters behave within the confines of religious belief and social custom, and so on. Martin is a fantastic story-teller, but I think his claims to a ‘realer’ medieval fantasy are hollow; but then, he’s telling such a good story – should he ever finish it – that I don’t think he needs to make that claim.)

As for the show, Benioff and Weiss are even worse at managing distance and time and understand how the various parts of a pre-modern society work even less, which means they tend to take Martin’s minor miscalculations (a two-month trip becoming a one-month trip) and magnify them (armies instantly teleport over continental distances).

Maybe somewhere down the line, when I have a bit more time, we can get a bit more into the weeds on how fast armies move and the complications of logistics that entails. For those who don’t want to wait and instead want some book recommendations, some good places to start for thinking about these problems are:

• J. Landers, The Field and the Forge: Population, Production and Power in the Pre-industrial West (2005)
• J. P. Roth, The Logistics of the Roman Army at War (1998)
• P. Erdkamp, Hunger and the Sword: Warfare and Food Supply in Roman Republican Wars (1998)
• D. W. Engels, Alexander the Great and the Logistics of the Macedonian Army (1980)
• G. Parker, The Army of Flanders and the Spanish Road (2004, 2nd ed.)

I especially recommend Landers, which offers a truly excellent overview of nearly all of the sticky, messy problems of creating, mobilizing, moving and paying armies in the pre-modern world (he stretches from Rome to the early modern in an effort to show the (very real) continuities in warfare). Unfortunately, the book is pretty expensive (as is normally the case with these sorts of studies) so maybe check your local library for a copy.