A big army, fearful and hateful of elves, is standing in front of the forest they all (or vast majority of) reside in. Behind them is a stream, and beyond the forest is the coast. What is to stop them from setting fire to the side of the forest close to them and letting it spread?

To clarify (I know this is very late and should ideally have been edited yesterday) — I want to see if it makes sense as something that has happened, and see if it is perhaps impossible for some reason. This is something I would like to have happen and framed as "that terrible thing we did during the war". Magic is not versatile enough to help either side. Perhaps if they came, at the height of summer, from the coast side by day and set several fires there, then by night, after the wind turned, they set fires from the other side. I'm simply not sure how possible it is to burn so big a place. I don't need it to burn entirely, for my purposes it simply has to have been gruesome enough to be a harrowing memory.

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    $\begingroup$ Your plot. This doesn't look like a problem with the rules of your world, but more like a problem of your story $\endgroup$
    – L.Dutch
    Commented May 31, 2021 at 8:47
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    $\begingroup$ Maybe the forest is wet and doesn't burn. Maybe there are daily heavy showers. Maybe the elves have fire extinguishing magic. Maybe the elves have prepared for such an attempt and have made fire-breaking clearings. Maybe the forest is holy and burning it would be a grievous sin. Maybe wood is precious in that locale. And so on. (And anyway, setting fire to a forest sometimes works but quite often it doesn't. Massive forest fires usually occur in dry places such as California or Australia.) $\endgroup$
    – AlexP
    Commented May 31, 2021 at 8:52
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    $\begingroup$ Are you saying "is it possible that an army could burn down a forest", or are you saying "is it possible that they could not burn down the forest"? I think it's the former, but I'm not quite sure. If it is the former, then I can't see why not, provided that you haven't already established something that should make it easy to stop them - for instance, that the elves can summon torrential rain whenever they like, or that the trees are alive and would massacre soldiers that got close enough for arson. (Even then, they could try fire arrows, in very dry weather it might be enough.) $\endgroup$
    – A. B.
    Commented May 31, 2021 at 12:36
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    $\begingroup$ @Riq Then it looks to me as if all the answers except thewildnobody's so far are answering the wrong question. They're suggesting ways you could possibly stop it working, rather than discussing whether it could work under normal circumstances. To be fair, your title literally asks exactly that, "what's to stop them burning the forest?", not "could they burn the forest?". You should edit the title - people are taking it literally. $\endgroup$
    – A. B.
    Commented May 31, 2021 at 14:02
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    $\begingroup$ P.S. Forest, as in natural forest, does not burn at all easily. Do not confuse it with the artificial plantations of firewood that burn so merrily in California. $\endgroup$
    – PcMan
    Commented May 31, 2021 at 15:18

17 Answers 17


Forest fires are a type of wildfire, which to spread effectively need at least two things:

  1. Sufficient dry starting fuel.

  2. Wind in the direction of spread.

If constructed correctly, it is conceivable that the non costal side of the forest would not experience a sustained wind coastwards, but would experience a sea breeze, pushing the fire front away from more trees and fuel. This doesn't stop anyone from methodically burning the forest down, but it will force them to put a fair amount of effort into it.

Forest fires are more complicated than this, read Wikipedia on wildfire models.

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    $\begingroup$ +1. I suggest editing to include the link to the wiki you mention (en.wikipedia.org/wiki/Wildfire_modeling). $\endgroup$ Commented May 31, 2021 at 13:36
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    $\begingroup$ This seems like nearly a frame challenge: we hear about forests where a single match can burn it all; but most forests at most times aren't that way. $\endgroup$ Commented May 31, 2021 at 22:04
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    $\begingroup$ I thought the sea breeze went in one direction in the morning and the other the evening, if this is the case, they just need to wait for the good moment $\endgroup$
    – Kaddath
    Commented Jun 1, 2021 at 16:28
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    $\begingroup$ @Kaddath, there are two different effects: sea breeze from sea to land, because the air above the sea heats up during the day faster then the air on land. During the night the sea cools down faster then the land, and since the land radiates heat out, it causes winds in the direction of the sea. If the land is properly covered and/or there is a hill in the way, the breeze from land to sea would be far less significant, weakening even more as you get further inland. $\endgroup$ Commented Jun 1, 2021 at 19:14
  • $\begingroup$ This could potentially work on flat land as well, if the forest is damp and cool, this will cause a bubble of humid, dense air, generating a similar but less intense "outward wind". $\endgroup$
    – IronEagle
    Commented Jun 1, 2021 at 23:52

The trees are fireproof.

The elves do not live in forests of lodgepole pines. Or maybe some used to but moved out when the forest burned. They live in redwood forests.


Why is the Redwood tree fireproof?

Redwood trees have very thick bark which has a lot of water inside it. They also do not have any pitch inside the trunks which is a very flammable substance found in many other trees. Another factor that helps to make the redwood trees fireproof is the fact that they do not have any of the resins that other trees like pine and the sap that the tree contains is made up of a majority of water also adding to the fireproofing ability.

Redwood forests of giant trees seem like prime elf habitat anyway. Also an elf with a bow and arrows in a redwood 250 feet off the ground would be an opponent to be reckoned with.

  • $\begingroup$ Great natural solution which also gives advantage for the elves to post watches high in the trees on the edge of the forest, giving the elves all the intel of approaching armies way ahead. $\endgroup$
    – Mixxiphoid
    Commented Jun 1, 2021 at 14:37

The Elves won't stop you because they are already setting fire to the forest.

Forest fires are a natural part of many forest's life cycles and can actually be beneficial in controlled burns. Letting a forest grow too long can lead to the next fire being to dangerous or affect forest health. So long as the trees have a fast life cycle it may be hard to eradicate the forest.

Evil trees

If these are magical woods you also have bigger problem. You walk into the forest to burn it down, and the forest might burn you down. Any attempt to set fire to the forest puts you in range of the forest. Once that happens your life is forfeit unless your ears are as long as knives. That is why the elves live there. It is a free military advantage as long as they don't chop down the trees and curate the forest with controlled burns.

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    $\begingroup$ Well, if the trees will attack them and are allies of the elves then they really want to destroy them. Flaming arrows or catapulted firebombs work from pretty far away. If they have cannons a "hot shot" (red hot cannonball) sets fires. $\endgroup$ Commented May 31, 2021 at 22:08

Elves are Celtic mythology characters for one reason: they live in the Celtic rain forest. It's a very humid forest where it rains nearly daily, maybe as wet as the equatorial rain forest.

Unless in a severe drought, any fire you try to start will soon extinguish itself for lack of dry fuel - unless it's extinguished earlier by rain.


Money, money, money.

What is to stop them from setting fire to the side of the forest close to them and letting it spread?

Forests are extremely valuable resources, and are most definitely things you do not want to burn down, particularly as warfare is expensive. It takes a very long time to rebuild a forest - they do not, oddly enough, grow on trees. You are destroying :

  • A primary building material for everything from houses to ships (in it's day) and just about everything else. Not every type of tree is ideal for each building purpose, so unless you have very selective fire, you can't risk it. Some of these wood types would be more valuable than gold in a wooden ship building era. Then there's the seige weapons and fortifications you could be building instead.

  • Manufacturing resource. It's not just the wood (used in everything from utensils to chairs and tables), but fences, weapons (!) and other things made of wood, it's the fact you can burn the stuff usefully to make heat for manufacturing lots of stuff you can sell and get rich on.

  • Food and medicine. There's a lot of wildlife and plants in a forest that you can't find elsewhere. Maybe it's annoying the enemy have it, but that's not a reason to destroy the asset. Keep in mind that kings and monarchs often grabbed their own private forests, not just to ride about in and take long walks, but for sound economic reasons. Some of these plants (and wildlife) can be used to make medicines as well.

Typically when you want an enemy gone, you also want someting else : all their stuff in your possesion. They will also make extremely useful slave labor for working in my wood-using industries (and other tasks my army is not going to do). So burning stuff down sounds nice until you think about what you're really burning - money !

Behind them is a stream, and beyond the forest is the coast

Beyond the forest is a thing to float wooden ships on and make even more money. Behind them is a thing to float barges and smaller boats on for rapid transportation of the spoils of victory (or more men if needed). You want to burn this down ?

Military campaigns cost (yep) money. Generally you don't embark on them simply because you hate the other guys. You want a payoff. You want their stuff, you want them doing useful work for free (or as little as it costs to feed a slave). You want your soldiers motivated by images of retiring to small farms with personal slaves and land stolen (eh, captured) from our enemies.

Exceptions to the rule :

You are e.g. Caesar and the German tribes have been raiding you and whiole you don't have any interest (yet) in expanding into their territory you would be quite happy with them starving to death for the next few years or a decade or so.

However even here you want to destroy their farms and crops (inducing immediate famine) and burn down their houses and infrastructure (because it screws their economy and ability to live in the area). Targeting a forest only works if you don't want the forest.

In your scenario (with a coast nearby) you're going to want the forest intact. Well, I would anyway.


You have access to lots of wood (edges of forest) and will simply build a lot of fortifications making the enemy getting out a problem for them and a potential source of tax income for you. "You have goods to send out, elf merchant ? Let's say 10% by weight as a toll fee. Or I bring back all my army while you fail to breach my line of fortifications."

This is why we have politics, so burning everything useful is not required. An uneasy deal is cheaper than a standing army, massive destruction and loss of resources to both sides.

So after some military posturing, a brief siege or two, the odd skirmish, peoples who hate each other write a treaty instead. Politician's spin it into a victory ("We showed them who's boss.", "They can't beat us.", etc).

  • $\begingroup$ This is one of the very few answers that address the real problem -- whether it makes any sense to burn the forest. $\endgroup$
    – Otkin
    Commented Jun 1, 2021 at 6:42
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    $\begingroup$ If I remember correctly, Sun Tzu said that maintaining an army of 10,000 infantry and associated cavalry/chariot units, including food, glue, and paint, runs 1,000 ounces of silver a DAY - and even more if you send them into combat. It's always about money. $\endgroup$ Commented Jun 2, 2021 at 14:51


There are mobile, sentient trees around. When you start spinning those sticks to start a fire, you risk getting walloped on the noggin' with extreme force.

Even if you try lighting fires by outsourcing fire staves, you are still in a position where you are open to retaliation by the treants. They love throwing immorally large boulders over large distances and they are quite the marksmen. This won't be symmetrical warfare because they can put fire out by patting on their fellow trees, whereas you can't even raise your firestarters from the dead once they've become paste.


Because the forest isn't as flammable as all that except in very dry seasons and because to set fire you first have to get close.

As others mentioned forest fires are a natural occurence and frequent fires can prevent entire forests burning down. You would have to burn the forest section by section.

Unfortunately each time you start a fire you have to get close, simply firing fire arrows isn't going to cut it as fire arrows burn out too quickly before setting a large enough fire. Additionally fire arrows aren't aerodynamic so they have less range and they are more expensive to make, meaning retaliation is much easier for elves shooting your fire archers. So you are going to have to build a fire big enough to burn a large section down, and build that in the forest where the elves will be hiding.

This is a huge problem: you need to bring enough people to protect the process of starting a fire while elves might attack you at any moment. And then what? Leave too early and the Elves can put the fire out before it has burned a large section of forest and you need to go in again. Stay too long and you are now next to a forest fire with disorienting and suffocating smog and the fire is spreading to your men as well.

Better to try a different strategy than burning.

  • $\begingroup$ +1. I think people underestimate how hard it is to set fire to a wet forest. Sure, in the middle of a dry summer in the right climate it’s relatively easy, but there are plenty of climates and forests where it’s almost impossible year-round. $\endgroup$
    – Michael
    Commented Jun 1, 2021 at 7:52

Technically Nothing

In the grand scheme of things, nothing prevents the army from trying to burn the forest in an attempt to deal with the elves in the forest. My thought would be that for an army to do that, their desire to rout the elves is more valuable and/or important to them than the acquisition of all the resources in the forest that they intend to sacrifice to perform the task.

I do not see a reason why it could not have been done in the past, or conversely, having these armies take advantage of fires that might have already sparked in the forests to continue their campaign. Torching the forest and letting it burn happily to destroy a forest may have served as a dire warning that this army is willing to literally burn the land to get what they want. In that case, the fire was as much the method as it was a message.

That an army is willing to callously scorch the earth and not care about noncombatants that might die in such a tactic is something that should be addressed as well. Such callous disregard for life probably has consequences.

... But Wait!

This does not mean, however, that the forest is one conducive to being torched for any number of reasons. Most of them have been mentioned in above answers in more detail.

  • Climate and location may limit the forest's ability to burn. Worse, the winds might prevail in a way that blows the smoke from those fires over the army, seriously impeding the army instead of the elves.
  • The elves, or the forest itself, has taken preventative measures against the forest burning. The how is less relevant for this question -- the point is that intentional acts are taken to mitigate fire damage. After all, a forest fire doesn't have to be deliberately set by invaders.
  • The trees themselves might not burn easy enough. Be they species that don't burn easily or tree that are augmented with limited magic to resist fire, there is enough flora in the forest that won't burn easily enough to make it a viable tactic.
  • The residents of the forest certainly won't stand for their home actively being set on fire and may take active measures against it if such a plan is known.

The Army's Side

There is also the army and the world surrounding the army to consider. Sure, they fear and hate elves, but what about the rest of their state/kingdom/country?

As one example, the forest that holds these elves may be sacred to the country's religion, or important to religious rites for some reason. Because of that, they want the elves out, but they can't torch this forest because that would be anathema to the religion of the land.

Counter to the first point, if the army's country hate elves already, their forests may be evil places that need to be cleansed by fire to burn the impure. As such, torching the forest may be the plan the whole time.

Going back to the first point, the forest is needed for resources for the kingdom. Be it food from the animals, or wood from the trees, the bounty of the woods are vital to capture. That they get to kill their feared and hated enemy to do this is a bonus. Can't use the forest's bounty if it's all been torched.

The Magic Question

I haven't even brought up magic into this. As this is tagged as Low Fantasy, I have strived to not really bring it up for individual points. However, it is important to know enough about your magic to know if arson is easier or harder with your limited magic.

It could be that this army has enough magical support to be able to start a forest fire, let it burn, and protect the army. This could make arson rise from a last-ditch effort to a tactic worth attempting to test defences.

Likewise, the inverse could be true as well. Defenses against arson are stronger than an army's ability to set fires.


The TL;DR version is that the question as asked, nothing stops the army from torching the forest (or trying anyway). However there are a multitude of worldbuilding factors that may both encourage and discourage such literal scorched earth tactics.


Most answers seem to focus on either a magical reason, or the fact that forests can be hard to burn down under the right conditions. But, I noticed something else that you said,

"the forest they all (or vast majority of) reside in."

As in, the elves we hate are mostly inside the forest, as in not currently waging a massive war against us, and a good way to get a big scary army at your door is to burn down their home. Not to mention, they probably know how to put out whatever fire you start, and barring that, how to kill you with their army as you try to burn them down. Once the finish with you, they will probably retaliate, witch is not good.

Another point is that similar sort of thing actually happened in the Vietnam war. The Vietcong were using the forest to their advantage, the U.S. tried to burn down the forest, and the result was notably not the U.S. steamrolling the Vietcong. People fight really hard to protect their homes

So, to summarize, burning down the forest would not only probably not kill all the elves, it would enrage them into attacking, witch they are currently not doing.

  • $\begingroup$ Actually the U.S. military was on the road to victory; it's just that the U.S. public opinion considered the cost in money, moral standing, and life too high to carry the war to the end of that road (oversimplified). They didn't burn the forest, they merely defoliated it, so the analogy isn't very good anyway ;-) $\endgroup$
    – toolforger
    Commented Jun 1, 2021 at 16:24

The elves place an enchantment around the forest that draws from the ley nodes running through the forest itself that makes the trees indestructible by fire, while also improving their appearance and limiting pesky underbrush, therefore, unless a stronger group of sorcerors engage them mortal fire will not burn down the forest.

The enchantment is maintained by the constant outpour of energy from the ley node which pools and moves magical energy tied to the life force of the natural world through various invisible connecting lines between places of dense natural life and health.

The post is marked fantasy :P


There were many good technical arguments made, and I'd like to make one logical argument.

This most likely cannot be done outside of extraordinary means like divine intervention / meteorite / sudden volcano opening up. Think about it: the elves have lived in the forest for hundreds of years. Anything bad that can happen to it, natural or man-made, they have seen it a dozen times over. For something as obvious as fire they will have precautions on the level of our own modern buildings fire safety. Definitely they will have concealed fire tranches and fire-watch abound. Even if you manage to start a fire, all they need to do is start controlled counter-fires to cut it off.

The same goes for any obvious hazard like a river dam upstream - if a passing army could think about it - creatures that lived here for generations definitely thought about it long ago.

IMHO, you best bet is some new technological advancement like poison gas, if you want it done fast. You can get creative with its effects, perhaps it does not kill elves directly, but drives local wildlife into a permanent frenzy. Maybe ultrasound generation mechanism doing the same. You can also limit its effect to the elves themselves or some animal present and abundant only in elven populations, to avoid your new weapon being a silver bullet in your world.

P. S. Diseases are a candidate, but probably would not work - they are slow and need to be extremely exotic to the local population (think bringing smallpox to Mezoamerica). Unleashing something like that will wipe-out a lot more than just the elves, aggressors own army included.


Pollution : The forest trees bring some poisonous gas when dying

The army could easily set the forest on fire, but not too far from the forest are also inhabitants, farmers, and fields that the nearby population heavily rely on for their food supply.

Eventhough the farmers (and their army) really hate the elves, they are aware that setting the forest on fire would bring death upon them. The winds can change direction really quickly in that region and would bring a disaster. Also the fields would probably turn unfertile and the rivers would be poisoned too. That would be a long term catastrophy.

Cutting a tree or setting it on fire is fine. As long as it is a single tree, the pollution is not a problem, but a whole forest would bring a huge poisonous fog and the army knows they can't do that.

  • $\begingroup$ That might actually be excellent as a consequence. Even works with things I have planned regardless. I can't find much about the effect of wildfire pollution on agriculture though $\endgroup$ Commented Jun 1, 2021 at 9:20
  • $\begingroup$ I was looking for this kind of tree as well but I couldn't find. I m not sure that exist on earth. But maybe in your world, you could define a tree that dies and would have such an impact. $\endgroup$
    – Pierre44
    Commented Jun 1, 2021 at 13:27
  • $\begingroup$ So something like poison ivy, or poison sumac? I like it. $\endgroup$
    – IronEagle
    Commented Jun 1, 2021 at 23:54

Why not burn the forest? Because big fires are nasty.

Here's some very real consequences that this fire could have, assuming that this forest is flammable, and coming mostly from the perspective of a Coloradan:

  1. Air quality goes way down. In a pre-industrial revolution world, a forest fire will be the worst pollution anyone has ever encountered. Ash rains from the sky, and even if the smoke isn't poisonous, it is thick enough in the air that it smells like fire for miles away. Seeing as the ocean is on the far side of the forest, it's likely that the breeze off the sea is going to blow all the smoke directly towards the humans.

  2. That river isn't going to do a thing. A sufficiently violent enough fire with enough of a breeze can easily jump a fairly sizeable river-- in 2020, a fire jumped not only the Colorado River, but I-70 as well. That's a big stretch of non-flammable area that the fire crossed, and it's not at all an uncommon event. Whatever is on the other side of the river, it's probably also going to burn.

  3. Superstitious people may fear that they have incurred some sort of divine wrath, due to the color of the sky. During a fire, the ash and smoke in the air turn the sun red. It genuinely looks like the entire world is ending, with the sky covered in clouds and everything bathed in an uncomfortable crimson light. Depending on the religion of these forces, they may know what happens when a large fire is underway and believe that the sky is turning red not because of the natural refraction of light, but because they have angered the gods in some manner.

  4. Hope you're ready for a flood! After a fire, the damaged forest can no longer properly absorb rainwater, leading to a higher risk of flooding. This is more common in fires in mountainous areas, but it may well work for you as well.

  5. This is not relevant to Colorado, but some trees (such as eucalyptus) literally explode during fires. The trees produce a highly flammable oil, and while this may not have any immediate impacts on your medieval forces (who would not be in the trees), it would probably be terrifying enough to dissuade future arsonists.


The understanding that they would be creating some really, really, coldly angry, long-lived elves, who would have just been given a lesson in genocide and become dedicated to vengeance. And probably be given help from elves living elsewhere. Resulting in:

  1. Anyone with a lit torch would be shot at the moment they came within arrow range of the forest.
  2. I would not want to be the leader who gave that order; I'd imagine that the elves would come up with something... special for them.
  3. The knowledge that for the rest of the army's (brief) lives, they will be hunted down.
  4. Consequences to their country: crops burned, fires set in cities, citizens killed, leaders assassinated...

Hating Elves does not mean hating nature.

The humans may have a reverence to the forest in a way that doesn't extend to the Elves living in it. They may consider destroying mother nature's magnificent creation as sacrilege. They may fear the Gods' reprisal if they destroy the world built for them in some petty conflict. They may even despise the Elves because they deny them access to the forests which they would otherwise like to use for industry or other purposes.

Whichever way you go, distinguishing between the forest and the Elves that live in it is a good starting point.


Here is a possible plot device that would explain why it didn't work. If the elves are hated so much, then perhaps they anticipated this event and took measures beforehand to prevent it. For example, perhaps the elves leveraged their magic to cultivate a type of ivy along the outer perimeters of the forest that is especially toxic to humans - but not to the elves. The army never had a chance to set fire to the forest in any substantial way, because they are driven back by clouds of thick toxic smoke.


The elves are hated, but they are hated because they're different yet an essential part of society and the economy.

So getting rid of the elves, however much they're disliked, is going to cause worse problems than leaving them be in that forest of theirs.

Let's instead declare an exclusion zone around the forest where nobody except our valiant patrols force that enforces the zone is allowed to go without permission (so that trade with them can go on, say some valuable resource only they know how to generate, and which they trade with your people for something they can't make, like luxury items or a favourite type of food that doesn't grow in their forest).


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