Had to divide this in two, because of the length it got to.

You could subtitle all these first three “Fuel,” really.

1) Food.

Many authors quote the statement that an army travels on its stomach, but few authors do anything with it. Where are the supply wagons, the long lines of cattle that surely must be slaughtered to provide all the meat that everyone seems to be eating, the cooks that prepare the stew or broth or salads? Where are the forage parties that bring in food from the surrounding area, if the army doesn’t bother with supply wagons? Where are the eventual replacements for the bottomless bags of dried rations that soldiers in other fantasy armies carry with them?

Each of these situations will have its problems that must be dealt with. The solution is to deal with them. You can get mileage and even, I bet, plot points out of it. But if you want your readers to believe that these soldiers really are eating, and especially if you want descriptions of lavish meals, you’ll have to study ways to take care of it.

Supply wagons? The main problem with long supply lines is that they can be cut. So perhaps an army can’t venture that far from a central storehouse because of that. Perhaps the other side comes galloping in, burns the supply wagons, and drives the cattle off. Perhaps the first army in your world that discovers an absolutely infallible way to protect their supply lines is going to win every battle. Play around with this. Have fun with it.

Foraging from the land? Well, the enemy might burn their own crops, to keep the army from taking them. (And then you get famines, one of those other problems that, for some reason, Do Not Exist in a lot of military fantasy fiction). There’s also the fact that, depending on the season and the terrain, there might not be very much to eat around, and the hit-and-miss factor of hunting is high. And if the enemy notices that the army is foraging, they might manage to lay ambushes for them in what look to be plentifully stocked villages; illusion magic could help with that.

Soldiers bringing supplies? The main problem is that there’s a limit to what a soldier can carry, and unless you give everyone a bottomless backpack, they’ll need to restock soon. Perhaps they stop by villages, perhaps they then resort to foraging, or perhaps they have a nifty magical solution, like someone teleporting in with food from the home front. All of those could be plot situations, as well- what happens when their tense visit to a village explodes in violence, or they eat something unfamiliar that makes them too sick to move for a day, or an enemy archer manages to take out the teleporter?

Paying attention to food difficulties could be a godsend where sluggish fantasy plots that are basically “army marches in, they fight, the army kills everybody, lather, rinse, and repeat” are concerned.

2) Fire.

Most armies burn wood. Okay. But where does the wood come from? An army should either be denuding forests as it marches along, or have a supply of wood brought in wagons, or be using small sticks and scattered bits of wood- all of which suffer the same problems as those ways of finding and transporting food.

Fire has a different but related problem, however, and that depends on the terrain. Wooded country? Not a problem. But when an army is passing through a desert, I always wonder where they manage to find that wood they’re burning. Ditto for grasslands, swamps (unless the author notes that the swamps have trees), mountains, and snowy wastes. Eventually, they’d run out of wood that they brought with them, probably long before they moved out of a big expanse of said country, and either have to go without fires or use something else.

Dung might be possible, especially on grasslands where there’s grazing animals around that drop large loads of it. Grass could work, though in that case the flames would burn pretty quickly and they’d have to have some other way of starting the fire than by using two sticks rubbed together. If they’re near a peat bog, they could use that, but the peat might be a bitch to dig up.

Or they could have no fires at all, which most fantasy authors only see as an option when enemies are stalking the heroes. Take note of it as a purely realistic detail, though. Do they have food that needs to be cooked, are they in a country where they would freeze to death without it, or do they use fires as a signal for sentries and scouts? If not, then there might be no reason for a fire, or only the commanders and other high-ranking people might have them.

3) Mounts.

Horses are marching fuel problems, since they eat a lot, and to keep in top condition they can’t graze all the time (unless they were originally wild horses, I suppose, and used to living on such fare). Warhorses and horses that draw big heavy supply wagons will especially need to eat a lot. They need plenty of water, too, which may limit the places the army can camp. And depending on the country of origin, there might not be very many horses in an army. If your country uses a typical hierarchical society based on wealth, then probably only the richest classes can afford horses, and certainly only the richest can afford the time and money and breeding that it takes to get steeds trained as good war mounts.

Also, what about that terrain they’re crossing? Horses will be good on grassland or in a forest with wide enough trails for them to pass. Only certain breeds of horses do well in the desert, there will be problems in the mountains, and it’s hard to see much use for a cavalry on an arctic waste where a magical blizzard never stops blowing. Before you automatically include a cavalry division, even for scouts (see point 5), ask yourself if they would really work.

The same problems, especially the fuel ones, apply to different kinds of mounts:

  • Camels. Hardy enough in the deserts, and the Bactrians do all right in cold, but elsewhere, their bad tempers and slower pace would probably make them second choice to other kinds of steeds.
  • Elephants. Oh, yes, they’re strong, but they eat and drink far more than horses do. If you’re going to include elephants in your armies, your readers will probably take interest in the supply problem that they don’t if it’s just horses and the usual hand-waving about “grazing.”
  • Donkeys/mules. Hardier than horses, they can serve more easily as pure pack animals, and they’re better in the mountains, and they eat less. The main problem, as with camels, is their tempers; a mule that decides it doesn’t want to pull its load up a mountain trail is going to cause backups all along the line.
  • Dragons. The advantages of them are obvious, which I think is why so many fantasy novels use them as war machines. But if the dragons are reptilian, though they might not need to eat often (just like giant snakes such as anacondas), they’ll gorge themselves when they need to. And since many authors represent draconic tempers as awful, they probably wouldn’t be willing to wait. An army would have to keep a supply of meat on hand at all times, just in case that was the day a dragon got hungry.

4) Sentries.

It irritates me when a passel of attacking heroes can just stroll straight into the enemy’s camp because the enemy sentries do stupid things like pace the exact same beat, meet in the exact same place, and yell out the exact same coded phrases all the time (why yes, hello again, Robert Jordan). I don’t think any army commander who’s managed to last in the field would be that stupid. The sentries are likely to have precautions, some obvious and not so obvious, to keep heroes from sneaking in, and if the heroes’ army doesn’t have them, it damn well should.

Among some of the more common-sense things:

  • Sentries that keep out of sight and quiet, perhaps in a tree, have a decided advantage. A scout snooping about is less likely to see them, while they have at least an even chance of seeing the scout. And if they’re archers, then that might be one spy who’ll take an arrow in his throat and never go wailing back to his masters.
  • Sentries may double back, use erratic speeds, and show up at unexpected points in their courses if they do pace. That ensures a surprise to someone who thinks he’s estimated their beat and is creeping across the lines.
  • A system of passwords would almost certainly be in use if the sentries had to go and report to the commander or general. A hero who steals a sentry’s garb and after that waltzes through the camp makes me snort through my nose. It’s as though the stupid enemies just look at the clothing and decide, “Yep, he’s passable!”
  • When sentries changed shifts, and especially if they called out and no one answered, I would expect them to linger and wait, rather than blithely marching into a trap. And, of course, finding an unconscious or dead guard is just the thing to rouse the camp, assuming the hero has managed to get in undetected. He should at least take time to hide the body.
  • Why should sentries watch alone when they know the enemy is out there and might try sabotage? Pairs or trios guarding a big army would make plenty of sense, as thousands of soldiers would mean that the same person wouldn’t be watching night after night, and they could support each other if trouble came calling.

5) Scouts.

Little attention gets paid to them, poor dears. There’s the occasional messenger who comes dashing into a camp and flings himself down sobbing before the commander, usually right before the heroes’ army falls on the enemies like an A-bomb, but otherwise, they’re…well, out there somewhere, surely, doing important things, but not actually existing until the author needs one on screen.

An army advancing across enemy territory will need all the help it can get from its scouts. One man or woman alone can move more lightly and quickly than an entire marching army, can spy out traps that the enemy might have set up, can note features of the landscape that will prove a problem and report on them, and stands a better chance of going unnoticed. An enemy that manages to kill all the scouts and thus blind the army has an enormous advantage.

So, some ideas about scouts:

  • They don’t have to ride horses. Really. If their biggest concern is going unseen, a horse will be a hindrance rather than a help, since it makes more noise, eats a lot, leaves more recognizable tracks (and manure), and can’t climb a tree or wriggle into a tight space the way a hunted scout can. If the main concern is speed, then you might need cavalry.
  • Scouts with magic would be valued. Someone who can, say, pass telepathic messages back before venturing further into danger has three advantages: a) faster reporting, b) less chance of being stopped, as might occur if she tried to send a messenger bird, and c) no need to perform a physical return to the camp that might get her captured along the way or waste time.
  • Scouts will die, since the enemy will be watching for them and treat them as moving targets. Here’s a nice way to put your hero in a dangerous situation.
  • Consider having non-human spies. If the heroes have a mage who can use her eyes to watch the enemy through an animal (a concept I’ve seen in both Pratchett and Saberhagan), or an intelligent animal that goes out, watches, and comes back, or a shapeshifter, the enemy will have a harder time stopping them.

6) Weapons.

The heroes had better take good care of these, because, depending on the way you set your army up, they might not get any more.

For example, say there are a lot of conscripted peasants in the army. Where are they going to get their weapons? They may actually be forbidden to use things like swords in times of peace, or they may not be able to afford them. Perhaps the army has a traveling armory with it. Imagine what would happen if enemies managed to attack and make off with the wagons or chests or whatever else comprises the armory.

If a blade breaks or rusts, what will your hero do? Fetch a blade from the armory, maybe, or get a blacksmith to make him one. Either will necessitate some kind of presence there (and an army with a lot of horses will probably have a blacksmith to act as farrier anyway). It may take time and cost some money, and if the enemy attacks the next day while the army is peacefully sleeping, the hero might be without a sword.

Archers will use up a lot of arrows, often without hitting anything. Have them scour battlefields afterward for the leftover ones. Or show bowyers and fletchers traveling with the army. Do some research on bows, too, to make sure that your “fragile and delicate” archer heroine can actually draw the bow she’s using. It takes enormous strength in the upper arms to pull the weight of the bigger ones.

What about artillery? Well, most fantasies are reluctant to allow gunpowder to intrude into their worlds. But you might have big, clumsy cannons, which will almost certainly need to be drawn around on wheels, get stuck in mud, require horses or strong, patient men, take time to load, and require teams to do said loading, pulling, and care of the gun itself. In a world without gunpowder, there will probably still be catapults, ballistae, special siege towers, and so on. They share some of the same problems, particularly “What are you going to make them out of?” for siege towers, and getting stuck in the mud and ditches if they have to be pulled long distances.

7) Commanders.

This depends on the size and condition of your army. If it’s small, a few hundred men, then the commander might have time to see to most problems himself. After a long stretch of boring waiting, he might be glad to.

However, in a huge army, with thousands of people and where important things are happening all the time, the highest-ranking commander or general has no particular reason to take precious minutes out of her day to interview the newest recruits who think they’ve seen ghosts at night or something of the kind. That’s why she has juniors in rank. The juniors will probably take a look at the problem first and see if it needs to be passed up the line, and even then, it will probably go to a second-in-command before the general or high commander herself.

(This is included purely because I’ve read one too many fantasies where the heroes are taken captive and marched through thousands of soldiers to see the general at once, when there’s no evidence that they’re particularly important to the opposing side. Now, if the author indicates that there are high ransoms for them, or if one of the heroes is stupid enough to blurt out that he’s the opposing commander’s son or something, that might be different).

The navy will be tomorrow, I think.