How long will it take for my medieval army to travel?

Question

This question is complicated, so hang on. A medieval army made up mostly of foot soldiers wearing plate armor (although there are cavalry, they're going at the speed of the foot soldiers) with enough supplies to last them the journey carried in horse-drawn carts that go at the same speed as the foot soldiers. The land they walk contains enough water for drinking, cleaning, and other purposes. The soldiers walk for twelve hours every day.

The total length of the journey is roughly 360 miles (579 km). Of that, about 150 miles (241 km) are in grasslands composed of rolling hills while the rest of the journey is in forest. None of the march in the grasslands is on marked roads, while half on the walk in the forest (105 miles or 169 km) is on maintained roads while the rest is not.

The army leaves in the middle of November (I don't use exact dates in my story, but if you need one, say November 15) and the area has a climate similar to that of the states of Virginia and North Carolina.

The army collects more soldiers as they go. They start the journey with 5,000 soldiers and end with 25,000. For the sake of the question, let's say they collect new soldiers at a steady rate. I don't know how this would affect the army's pace.

All of this is really for the background detail of whether they arrive in winter or spring, but still, if the army makes no long stops and keeps a steady pace, how long will it take for the army to get from point A to point B?

I have a hard time figuring this out because of all of the details, but here's a source I found. It doesn't talk about biomes, roads, climates, and gathering more soldiers, but it has some details about pace that might help.

Answer 1

You specified that the soldiers walk for 12 hours per day. If that is the case, expect them to do the walk in less than three weeks (12 hours at 2 mph means 15 days if they can travel direct line. Round up for diversions from that route, but 2 mph is not all that fast as a hiking speed.)

That is not realistic.

Your army will be required to break camp in the morning and to make camp in the evening. Or more likely soon after the noon. 5,000 people are much harder to move than 5 or 50. The food they eat will not come out of a tin can, and cooking cannot be done on the move. Water supply will be a major concern. Once you reach 25,000 troops, most likely the first will already make camp by the time the last will depart from the old site.

You specified a medieval army. By and large, those were not nearly as professional as the Romans a millenium before. With well-trained, well-led forces, it might be able to reduce the time to make camp. A typical medieval mix of feudal levies and nobles is less proficient.

Depending on the weather, tens of thousands of marching boots and hooves could wear the grassland into mud. Put horse-carts into that (not ox-carts or mule-carts?) and you go down to a snail's pace. Snow might further complicate things.

If you look back in history to the Roman precedent, your force might march less than 10 miles a day in much less than 12 hours. A commander in a hurry might increase this, while bad conditions might slow them down.

With a disciplined force, call it 40 marching days, with 10 non-marching days in between for the occasional rest, or until engineers improve a ford, or until a nasty rain ends.

With an untrained force, you might be forced to make winter camp for several months. Departure in November, arrival sometime next summer?

Answer 2

Historical example

We have plenty of historical records of large armies travelling up and down the thousand kilometer long Spanish Road, from the Netherlands to Italy, in the Renaissance and very Early Modern times. The average speed is well documented to be something like 14 miles or 23 km per day; or actually anywhere between 16 and 33 km per day, depending on weather, organization, urgency and so on.

Just to make it clear, the Spanish Road was a route, not an actual road. There were no trans-continental roads in the 16th and 17th century. Some parts of the route were easy, some were harder; after all, it did cross the Alps, usually though Valtellina -- there is no way to go from Italy to the Netherlands without crossing the Alps.

I would say that this real-history example is plenty good enough for fiction.

Answer 3

You should count a minimum of two months. But if you want to make any plans requiring the presence of the army at point B, allow three months.

The figures from your source are for marching in summer. During the winter, they become impossible because there just isn't enough hours of light in the day, and some of those hours have to be spent setting up and dismantling the camp, preparing food, maintaining /repairing the gear etc. More walking time will be lost when the rearguard waits for all other regiments to march past before setting off; still more time will be lost when the vanguard has to stop early enough in the day to allow the rest of the army to catch up before sunset (which means that the army will slow down as it grows). Parts of their journey which are not on paved (rather than just "maintained") roads will be hard on the wagons, which will slow everybody down. All told, your army may be left with as little as 3 hours of walking per day on average, allowing it to cover anywhere between 6 and 10 miles, assuming no traffic jams, no taking a wrong turn, no holidays religious or otherwise, no rain/snow making roads impassable etc.

Answer 4

So, my experience Hunting:

Through relatively flat/rolling tracks (equivalent to your Meadow) it was a comfortable about 3-4 Kph (That was with a 5 Kg Rifle and around a 20 kg Rucksack). I'm not super-duper fit (in the process of getting fitter), it was uphill and downhill, but not so steep that it was difficult. I did have to stop after about 2.5 hours for a break (about 30 mins). I reckon I could have kept up that pace in that terrain for a full day of walking. Call it 8 hours of walking - around 24-32 Km. So your 241 Km journey across grasslands and rolling hills could be done in around 10-15 days - As you'll need some rest days to gather supplies/food etc.

However, when I was going on an actual hunt and going through the Bush (aka Forest) - it was more like 1-2 Kph. It does depend on how thick the forest is, but yeah, it's much slower going and in addition (if the canopy is very dense) the hours in which there's enough visible light to safely walk in is shortened by potentially 1-2 hours each side of daybreak.

So, 8 hours again, that's 8 Km a day (I'm picking the lower number because a single Human moving through the forest is one thing, 25,000 humans is quite another) - and so this second part of the journey would take around 30 days (again, we need rest days and re-supply days).

All up - you are looking at about a 2 month journey minimum.

Things that will speed up or slow-down your journey is your logistics. Assuming Someone slightly smaller than me - so a 70 Kg Male (160 pounds) and the same weight as the pack I carried (25 Kg of weight or 55 lbs) - you're burning around 500 calories an hour. So that's 4,000 calories burned just on the marching per day. That's about the same amount of Calories that a 24 hour ration pack/MRE for most modern militaries has.

To give an idea - your 25,000 person Army needs around 100 million Calories per day. That's the equivalent of hunting 625 deer every day - or 100 Modern day grain fed cows. Of course, they aren't eating all their calories in Meat - but you get the picture - lots of people, doing lots of hard work means lots of calories and needing lots of food.

And you need that for every day, not to mention the Water (I easily went through several litres of water per day).

If the route is 'known' - that is, there are maps and areas where resupply is easy or they know how far it is to the next stream/river or where the game is, then you could possibly justify just under a 2 month journey, especially if the Soldiers are fit/professional/disciplined.

However, if the route is unknown, the Army will most likely at the tail-end of the day make camp earlier if it is close to a strategically sound position (e.g. near a water source or near where there is plenty of game) then they would stop and make camp earlier and this could seriously slow down progress. As others have mentioned, if this takes place over Winter, they would most likely walk part of the way until the weather was too bad, then make a Winter camp, going back on the match when the weather is more donducive.

TL;DR - 2 Months best case scenario - but due to various factors could easily be longer.