Dedicated castle assault unit

Question

Medieval warfare can get ugly, particularly during sieges. Most will agree that the best course of action is to sit tight for a year or two and hope the defenders starve before your attacking force dies of illness. But sometimes that's not an option, maybe the emperor is impatient, maybe enemy reinforcements are approaching - the castle must be taken now or not at all, which leaves no option but to assault the walls.

Desigining a particular large country for my world, one I will henceforth refer to as the Empire, I have thought it appropriate that a country of such military pride and might would have a dedicated unit trained and equipped to excel in assaults on castles and fortified cities. The question is how would that unit look?

Size and purpose

Looking at the general size of Empire's army I would say the unit should be at most 4,000-5,000 men in strength (that only includes actual fighting force, the stableboys and other support personnel are outside of that count)

• The primary purpose of the unit is to play the primary/major role during an assault on enemy fortifications, be it castle or walled city. By assault I mean trying to go over or through the walls, rather than wait for a surrender.

• The unit is not expected to maintain a siege and perform an assault on its own - other non-specialized units will likely be present. EDIT: To clarify, the specialised unit will act as part of a larger army, but it is expected to be centerpiece/vanguard during the assault.

• The unit is of course expected to fight in open field when necessary, but in this case it will likely take on a secondary/supporting role.

What are we attacking?

The fortifications in question will not be unlike your average medieval castle or walled city.

• Expect one or more layer of stone walls.

• There may or may not be a moat.

• There may or may not be siege engines on the walls and towers.

• The defenders will likely have at least one mage or wizard (more about magic below)

Available technology

In general the technology can be described as high medieval ages, with some differences. Expect enemy to have equivalent technology (we're not fighting barbarians)

• No gunpowder

• Steel and iron are primary metals for weapons and armor

• Wide variety of armor available - from leather through mail to full plate.

• Wide variety of weapons available - if it feels like it belongs in a medieval setting, there is a high chance it is available in this world

• Regarding the Empire in particular: slightly inspired by Roman and Byzantine empires, the Empire has above average technological expertise in engineering and you can expect weapons and armour to be of above average quality. The roads within the empire are also well developed which may or may not matter if the unit were to include permanently assembled siege engines of sorts.

Magic

Magic exists, but it is rare and has limitations. This is war however, a matter important enough to include it. Assume 1 mage or wizard per 1,000 troops at maximum and it would be prudent to assume a similar ratio for your enemy. I will do my best to describe what can or cannot be done with magic, or - more accurately - what these mages and wizards can or cannot accomplish with it.

If you have any doubts or specific ideas requiring magic feel free to ask in the comments.

• Magic is tiring - Usage of magic will gradually tire out the user. More power and complexity of the spell - more exhaustion.

• Wizards and mages have the ability to electrocute, freeze, set on fire, or otherwise un-alive their enemies. A single spellcaster dedicated to that purpose can probably eliminate several hundred non-magical opponents over the course of a battle, provided he survives and has opportunity to recover his strength.

• Magic can be used to shield the user and nearby allies from (non-magical) projectiles. Such a shield can be maintained for minutes up to an hour depending on intensity of fire - more kinetic energy of projectiles means less shield endurance. The shield must be actively maintained by the caster.

• Magic can be used to shield the user and nearby allies from magic. Typically this kind of shielding lasts less under fire than the one above and will natrually lead to duels between mages/wizards. The duel is essentially a game of five-dimensional speed-chess and normal troops can be of great assistance by disturbing the enemy mage while not allowing your own mage to be disturbed by enemy troops.

• Magic can NOT be used to blow up walls or gates.

• Mages and wizard have an ability to communicate telepathetically with anyone on the battlefield, but they can only "transmit". Two magic users can establish a dialogue by using their respective skills to talk to each other, but communication with non-magic-users is one-way.

• Magic can be used to a certain extent to manipualte the battlefield - dry the mud, create smoke screen, potentially clear certain obstacles (like spikes or traps)

EDIT: Answers to questions by Nosajimiki in the comments:

• What is the range of magic spells? - Depends on the spell. If we're talking projectiles then most mages can compete with crossbows and longbows in terms of range. In terms of shields the question is not as much of range but of area (ties to the next question). The shorter the range of the spell the easier and less tiring it is. It is also significantly easier to conjure a fireball and propel it 100m than it is to conjure it 100m away. The mentioned telepathy can be used by ranges up to about 5 km.

• Is it more exhausting to defend a larger area? - Yes. And it works int wo ways. Not only is the shield itself larger and more tiring to maintain, larger area will mean more projectiles imapcting it, which makes it even more tiring.

• Do mages need line-of-sight to attack someone or can they lob spells blindly over the walls? - Line-of-sight is advisable. They can conjure a fireball and throw it over the wall like a grenade - slightly more difficult than just throwing fire into someone and there's no guarantee of hitting the target.

• Can they kill more people if they are packed close together? - In most cases yes. If a spell sets 4m^2 on fire, it doesnt really matter if theres 1 or 5 people in that area.

• How effective is armor at protecting against magic? - The effect is non-existent to minimal. Shields (hand-held, non-magical) can sometimes save a man, but only by merit of being a small protable wall - the shield and/or the person behind it would still need to withstand the imapct/heat/electricity. Protection is at best equal to protection from the natural element used against you, and at worst there is no protection, depending on quirks of the spell used.

• And can mages detect eachother out of a crowd? - To a certain extent. Whenever a mage prepares to use a spell he draws energy, and when casting he releases it. Those fluctuations can be sensed by other mages. How accurate that detection is depends on power of used spell and distance between mages. If a mage in the city uses a rather powerful spell, a mage in siege camp can sense that "somewhere in the city". At battle ranges the mage will detect the exact direction an approximate range, and he can point a finger at the squad of people that contains the mage, even if he's not sure which of them is it. Using telepathy is slightly different - using it to "touch" a mage or someone in his immediate vicinity will reveal your exact location to him.

My thoughts so far, which you may or may not agree with

• Due to its specialization, the formation will likely require little to no cavalry, with possible exception of general's bodyguard, who could benefit from mobility. On the other hand, keeping one of the mages with the general could enable him to give orders at a distance.

• While longswords are the preferred weapon of kinghts, one cannot deny the usefulness of a shield when assaulting the walls. I'd think shield and one-handed weapon could be the preferred equipment of infantry of this case. Limited swing range is likely a good trade in this case.

• I am uncertain how useful missile troops would be. On one hand they could harass the defenders, but on the other battlements offer a good protection from bolts and arrows.

• Due to specialized nature of the unit and good engineering and ifnrastructure in the Empire the unit could potentially have a couple of "permanent" siege engines. A siege tower with iron or steel armor could certainly be useful, but I can't quite convince myself about practicality of pulling it along whenever the unit goes anywhere.

Measure of success

To summarize, the question is: what would be the composition, equipment and tactics of a specialized unit for castle assault within the constraints presented?

The unit is meant to perform well enough that it somewhat "legendary", though these legends are of course overblown. It is, however, supposed to be rather effective at its intended purpose, ideally not suffering ridiculous losses in the process or bankrupting the Empire with the demanded equipment.

Answer 1

Four-Pronged Approach

Prong #1 Mage Corps

1. 4-5 mages, one highly skilled, the rest apprentices
2. 200 mage support troops
3. 50 guards

Mage Corps priorities:

• Neutralize enemy mages: Apprentices work in shifts to tire out the enemy magic users employing hit and run tactics. Support troops specialize in distracting enemy mages providing supporting fire and using tactics meant to disturb the enemy mages. This effort will be in coordinated attacks with the mages directing their support troops. The highly skilled mage will then move in to duel the worn out mages and neutralize them.
• Eliminate enemy siege engines: The mages will burn down any and all defending siege engines. This is necessary to be able to set up the unit's engines. This should be trivial for the mage corps once the opposing mages are neutralized.
• Protect the trebuchet corps
• Support the direct assault (from a distance) after the wall is breached
• Relay messages from the information corps to the enemies within the keep

Prong #2 Trebuchet Corps

1. 10 teams of 50 (total 500) engineers, woodworkers, laborers, and smiths will build the trebuchets on the site dictated by the commander.
2. 10 firing teams of 10 (total 100) will operate and fire the trebuchets. Team consists of 1 captain, 2 spotters, 4 loaders, and 3 alignment crew. Non combatant support teams will gather stones for ammunition.
3. 10 caravan teams (non-combatant), transport crew for the trebuchet parts.

Trebuchet Corps priorities:

• Crumble strategic defensive locations like towers, barracks, etc. as identified by the spotters and captains.
• Launch diseased or poisonous items into the enemy keep.
• Breach the wall with continuous fire at the specified entry location.
• Making moat bridges if needed.

Prong #3 Information Corps

1. 100 Scout rangers
2. 20 information specialists

Information Corps priorities:

• Identify enemy's supply chain and direct main army to disrupt them. Extra coordination is needed for walled city assaults.
• Determine the size of the garrison in the keep, and determine the starve out time. The more troops they have the faster they'll run out of food, the fewer troops they have the easier the assault will be. Report the results to the commander, and develop a strategy. This is especially relevant in a walled city breach.
• Sabotage water supply if possible (higher priority for walled cities)
• Find other points of leverage to persuade individuals inside the keep to abandon it. Encourage enemy deserters by way of bribes, clemency, etc. Relay these messages to the inhabitants of the keep by way of the mages.
• Identify and eliminate attempts to disrupt the units supply chain.
• Prevent anyone from escaping the keep on breach day, so that no one knows how they did it so future enemies cannot develop countermeasures.

Prong #4 Breach Corps

1. 200 squads of 10 men each (2000 men). Squads consist of 2 heavily armored swordsmen, 2 lightly armored spear-men, 2 shield bearers, and 4 crossbowmen.

Breach Corps priorities:

• Guard duty prior to breach day
• Placing Moat bridges (if needed)
• Raid the keep

The squads move in carefully and slowly with substantial ranged support from their crossbowmen and back line mages. The primary function of the non-crossbowmen is to protect the crossbowmen, and give them time to reload. The squads have also trained to be able to merge members with other squads in the case that some of them are separated or killed. If the information corps have done a good job at poisoning/starving/demoralizing the enemy they shouldn't be able to put up much of a fight.

Answer 2

I like the answer by Mathaddict, but I want to add a couple of thoughts:

• Mines (in the traditional meaning of the word) or Saps
  Dig a tunnel to the wall, shoring the roof as you work. Under the wall, dig a cavity, again with wooden beams. Then fill it with flammable stuff and torch it. The cavity collapses, and so does the wall. Gunpowder would have helped, but it is not strictly necessary for a mine.
  You can get peasants for the grunt work, but knowing how and working at the tunnel face is a job for combat engineers (sappers). Ventilation by fire, detection of countermines, ...
  Can mages accelerate this work? Or at least look through the Earth to tell who is going where?
• Pavises and Trenches
  If mages cannot blow gates, then they should be unable to blow holes into mobile wooden walls, either. There might be some combination of that and Vauban-style siege trenches. If mages are your snipers/artillery, then counter-artillery tactics might make sense.
  Again peasants to do the digging and fetching, with combat engineers to tell them how.
• Heavy Assault Infantry
  In a stereotypical medieval realm, good weapons and armor go to the mounted knights. Sure, they're also trained in dismounted combat, but if the assault is going to be bloody, why waste generalists on specialists' work? Generalists who fill an important role in local government, at that?
  Your Empire can afford heavy armor for a thousand commoners, and train them year-round. That is something no petty kingdom would do. These assault troops are more expendable than noble knights, and they know it, but if they serve their twenty years in the Assault Corps (three, four actual assaults?) the veterans get a cushy job in the Imperial stables or as sergeant in the city watch.

Answer 3

Magic is the key here

Direct assault on castles was a very dangerous, almost suicidal endeavor in Middle Ages. Any specialized team can suffer 100% casualties during an attack, and no amount of training or armoring can help that. Yes, you can train your special team, and it may even deliver you a victory, but then you have to do it all over again.

On the other hand, special teams like catapult crews can enjoy longer lifespans, allowing for a greater level of training. Also, you can go with Ninja-like teams which would infiltrate the castle stealthily rather than openly.

However, if you need warriors that are not only strong in hand-to-hand combat, but also have a good chance of survival through the storming of a castle, magic looks like the only option. Your special team would be somehow shielded during the attack and would be able to climb the walls without losing many of its members. Once on the walls, odds between the attackers and defenders are more even, and the team may complete the mission and go on to live after that.

Answer 4

TREBUCHET YOUR WAY IN

For me a specialzed unit of assault would be a great team of engineers and some mages to help. Your ingeneers will be also combatants hungry for more kills to add to the count. Given that the mages get tired of deflecting enemy projectiles, a steady rate of fire will tire them out quickly.

1 - Preparing the siege. Use your mages to heat metal plates to create trebuchets easier, better, deadlier and on spot. Your trebuchets need to be easy to reaload to keep a steady sustained rate of fire. You dont need to travel with heavy trebuchets all around the world. Build better stuff only where you need them. Your unit will be specialized in building these things, they have been trained and have top quality materials and knowledge on how to build the best trebuchets that the mankind can imagine. Also use the mages to have deadlier precission of the projectiles, have them hit where you really want: towers, battlements, doors, arrowslits...

2 - Sneak and blind. Advance a small group of mages and warriors in the middle of the night to a distance where the magic can reach any wooden structure on the wall and burn it. If your mage does reach more than the reach of a long bow your guys are safe. Create a smoke wall in between your troops and the castle to be sieged. Burn the door.

3 - Stone time. Imagine a great wall of smoke and stones coming from different directions. The defender mages will not be able to block all the projectiles and eventually the death count rises. Throw them something flammable too like huge ceramic vases with tar in it. With steady fire even the stone walls will perish as they lack mortar and rely only in gravity and weight to stand.

4 - Psychological warfare This is the main ingredient. Have your enemies fear you. Have the mages drawing the devil face on the smoke wall before the flaming stone comes out hitting the insides of the city. Scream inside the the heads of the deffenders, use all of the simbology available to imprint fear of your unit into them. Have the defenders know that when your guys show up bad things are about to happen.

5 - Assault time. Given the mess of the smoke, the stones and the fire, move your grunts to the walls and have them climb and assault. These should be the guys that die, not your specialized unit. Stop the trebuchets and use the mages to control the assault and coordinate it. After the first troops break in and is relatively safe for your special unit to move in, have them go to better coordinate the assault. Spread fear and death wherever they go, they should be the symbol of death and should be there spilling guts.

You dont want an ODST type of unit to climb up and honorably die. You want a special task force, rude dudes with thousands of battles behind them, mages that eat skulls for breakfast but also sharp experienced guys that know how to keep themselves alive and how to deliver death efficiently.

Answer 5

It sounds like you are looking more for storm troopers than siege engineers

I would recommend certain criteria for such troops

Soldiers

• The Roman military manual that was used well into the renaissance called De Re Militari calls for troops to be drawn from the countryside as they are stronger, are used to the hardships of the outdoors and the city folk are too lazy and soft. Not a big deal but it adds some flavor to the troops.
• As for the numbers, I would devote all of them to assault infantry and like the roman legions just draw in auxiliary troops to fill support roles.

Armor/ Weapons

• I would equip them with a gambeson, chainmail and either a hardened leather cuirass or a steel one. That would be enough to stop a fatal longbow shot to the chest at all but short range. As long as they live through the battle they can probably be healed, perhaps by magic?
• I wouldn't bother with more than the gambeson, perhaps chainmail at most, for the arms and legs. They will be moving their arms a lot, such as with climbing ladders and if they wear too much armor it would tire them out. Middle to later Byzantine infantry didn't wear anything over their arms and legs usually, preferring to fold the sleeves of their gambeson up as a pauldron sort of armor.
• Make sure they have a reinforced helmet, since that will be taking the most blows. Their head will be the most exposed when climbing a ladder and usually is a prime target, the Romans put horizontal bars across the tops of their helmets when fighting the Dacians and the Normans started making theirs out of a single sheet of metal rather than riveting together the parts of the helmet. Later medieval knights also sometimes wore two helmets, a close fitting cervelliere or bascinet helm under a great helm (The tomb effigy of Edward, Prince of Wales shows this well).
• I would give them larger shields like a roman shield or one of the larger styles of Viking shield. That would protect them from arrows until they get on the walls. Once on the walls they could be discarded for a smaller shield, like a buckler, that is better in close quarters. A Heater shield would also be a good all round choice.
• I would also arm your troops with a mace since it is a good all around weapon and can be used to knock open smaller doors.

Mages

• I would have your 4-5 mages focus only on protecting the lead elements of the assault. As long as they can get a foothold on the walls, they can overwhelm the enemy mage with numbers. The mages power could be conserved by using armored wheeled covers over their troops to protect them from arrows and only have to worry about siege engines and enemy mages.
• I would also put your mages, if possible, in the same exact uniform as the rest of your shock troops to avoid being marked as a valuable target.

Siege Methods

• For actually taking the city I would have my troops use a battering ram, ladders, and undermining. Dirt ramps to the top of the walls are the traditional Roman tactic but I worry that the enemy mages would mess with it while my troops were asleep. Siege towers I would also worry about since they are such a large, valuable target for enemy artillery and mages.
• That being said, siege towers could be useful in a different way, they were also used to gain a height advantage on the walls so your archers can shoot down on theirs.
• The undermining would be done by siege engineers and would collapse parts of the wall by tunneling under it and lighting it's supports on fire. The Greeks came up with a curious way of discovering this by placing a bronze shield in the ground and if digging were going on near it, the vibrations would make a sound.
• Ladders are pretty straight forward but the Assyrians were famed for their troops being able to climb siege ladders without using their hands, holding their spear and shield ready to fight the moment they got to the top of the ladder. Ladders also require archers to clear the walls a bit, they don't have to be effective at killing the enemy, they just have to make them keep their heads down.
• Battering rams are a bit underutilized in modern works. Until after the crusades, most castles didn't use mortar, they were held together by gravity, for a major example, Vienna didn't get a rework to it's walls until after the Ottoman invasion in the 16th century. So in ancient times, battering rams were used on walls. They were used on shallow earthen ramps to knock loose the top half of the wall. Then it could be stormed.
• You could still use it on the gate if you want but be warned, gates usually have the strongest defenses, multiple gates, and murder holes. Better to attack somewhere softer.

Assault

In the actual assault I would go with one of two plans usually

1. Draw up my most of my army and have them attack as much of the walls as possible to spread the defenders thinner. Then have my storm troopers attack the point I really want to take. After they punch through the walls they will move to the streets and secure a small mustering point inside the walls for the rest of my infantry to move through. Once the bridgehead is secured by my other infantry I move them back as reserve troops.
2. A tactic in the byzantine military manual, The Taktika, calls for continuous assault on the walls. Split the army into two shifts and have them attack in turns. Personally I would keep my storm troopers out of these attacks all together to keep them as fresh as possible. After the enemy is sufficiently worn down I send them in on one of the assaults and repeat plan 1.

Answer 6

Frame challenge! Historically, through the middle ages, subterfuge was a reliable and often used way to take a castel or city. The process:

• find a contact within the besieged castle/city,
• bribe them or otherwise get them to open a small gate or door,
• sneak into that door with a small hand picked force
• open the gate and hold it against defenders until the major force can enter

Yuval Noah Hararis book on medieval "special operations" has several examples.

In the middle ages and early modern ages, there where no dedicated special ops forces to do these things - there where low nobility who knew each other, from these networks the core of a small force of reliable fighters could form, augmented by more or less hand picked fighters from the larger force. Your fictional empire is probably better organized than medieval kingdoms so it might have a "spec-ops" unit. This could be made up thusly:

• A few dozen to a few hundred fighters that can fight as armored infantry with the usual weapons (ranged and melee). They fight dismounted but are trained to ride, to perform long marches quickly and to move silently. I don't think special fighting skills are needed - if heavy armor is present on the battle field grappling + dagger would be trained by many fighters anyway

• A rather large concentration of mages: These help with communication and from your question it appears that a mage is a rather powerful in a battle, if well protected - think holding a guardhouse against the city guard!

• a handful of seasoned spymasters who did this a few times before, these try to gather information and ultimately find the person to be bribed

• the head ofthe besieging army is the head of the special assault force: It is far to important to fully delegate to an underling, choosing whom to bribe and with what is a political decision and the person to be bribed will want a high level meeting to establish trust.

Alternativly or additionally, you could pick up another tradition of warfare: It was (ancient times through antiquity, medieval and early modern age - sometimes until today) customary to massacre the defending forces, and often many of the inhabitants, if a fortress put up a reasonable fight. Think of what the greek heroes did to Troy. War is hell, "honor" in a military context means (among other things) to not give up ones post - bad luck for the town's populace if the commander of the defence wants to make a name for himself by putting up a fight.

The brutality and utter disregard by most combatants for anyone vulnerable can be exploited: The mages can use telepathy to show, in graphic images, the towns populace and defenders what will happen to them if they don't surrender, as well as provide cues on how to organize a mutiny against their uppers. In fiction, warfighting tends to something done among professionals. In reality, it where and are civilians who suffered most.

As a tactic or strategy, this implies the following:

• The attackers are principally able to overcome the defenses, either by force or subterfuge or by a long siege - the threat has to be credible
• the attackers will indeed massacre and loot the city if the defenders put up a fight
• the attackers will not loot, burn, rape and murder the city if it is given up - this requires a very disciplined fighting force. Your special ops troop might well be a sort of military police to keep the larger army in check.
• Not looting a city also raises the question how the attacking army is paid, again, this is something that IMO better fits a well structured empire than a medieval kingdom.

Answer 7

Trebuchets: An Alternative Explanation

While catapults such as trebuchets have already been proposed, why they would be so good was kinda missed. Based on the OPs clarified definition of how magic works in his system, the use of Trebuchets would heavily favor the attacker because of the sizes of targets. A trebuchet can fire much farther than a mage meaning that during the wall smashing phase of the siege, that the trebuchets would be too far away for defending mages to effectively target. So, both side's mages would be dedicated to shielding. However, the attacking mages only need to shield a few relatively small siege engines whereas the defenders have to shield the whole castle wall; so, even if the defenders have counter siege engines they will still expend all their energy much faster shielding than the attackers will.

So, not only will the bombardment of the castle shatter its walls, but it will force the defending mages to either not defend the castle from bombardment at all, or it will drain them such that the defenders will not have any mage support left by the time the attackers are ready to storm the city.

If the defenders chose not to shield the walls, they will be forced to abandon the walls to prevent from being buried in their rubble. This means that the attacker will be able to put a large number of holes in the battlements before the actual storming phase making it a pretty fare fight.

If the defenders choose to exhaust their mages to try to hold the wall, then they will still eventually be forced to abandon their battlements, but when the assault comes, they will be at a huge disadvantage because the attackers will have magic to spare but the defenders will not.

As for the troops you use to take the castle or city, you want to go with light infantry armed with shields and short weapons (like hand axes or arming swords) because heavy infantry, pike blocks, and Calvary will not function well in the rubble of the shattered walls.

Answer 8

If mages could buff their allies, a breach unit could be made of 10 foot tall, over-burly soldiers wielding a ram. An additional mage could deflect projectiles on their approach, or raise a mist to provide them with visual cover. If the individuals retained their buffs, they could easily become legendary as they would be mighty warriors even outside of castle siege scenarios.

Answer 9

So As I read your question and comment you are interested on building an assault unit dedicated to castle assault. Not the whole Siege warfare which can include artillery, biological warfare, construction of ramp, machinery and mine.

So IMO your dedicated unit is separated in three corps:

A/ super shiny heavy infantry. B/ Infiltrator. C/ Intelligence.

A/ Not super original you want heavy armored man equipped for prolonged close combat. Meaning the toughest armor you can get them with. A shield. Mace or short sword. In this kind of battle the balance between mobility and protection may flip toward protection. Those men climb ladders, assault breaches...

B/ Sometimes it is possible to infiltrate a few men into a fortress (even better if you can do it before the siege is laid). Those men are lightly equipped men that aim to infiltrate a fortress in order to shorter the siege: For example they can try to assassinate an enemy commander. Start fire inside the wall, burn the granary. Kill the herd (sheep, cow ect...). Pollute water well. Sabotage of enemy defense like drawbridge and main doors. They as special forces (of today) picks their weapons and equipment accordingly to their needs.

C/ Covers either intelligence gathering as counter-intelligence (meaning giving false information to your enemy). You may learn troops position, organization, number. Even how do they react when you attack. This may prove invaluable. If the enemy commander believe you heavily outnumber him and that no reinforcement are coming because you defeated them. It may consider surrender. Corruption may be also involved. For example Napoleon took Vienna without a fight in 1805 convincing the commander the war was already over with the aid of a French spy.

Note : you did not mention your mage as able to cast more support spells such as invisibility, camouflage or reduce sound. If they can do that you may add a mage to the infiltrator. Else all your mage belong to A/.

Answer 10

Have weapons with longer range.

If your opponents are in a fortress, they will not be able to counterattack you without leaving the safety of their walls.

Burning mirrors, or arrays of burning mirrors, can be arranged to ignite any flammable object that is visible. Ancient romans used pyrography and lenses, they would have little trouble constructing these. Archimedes is credited with using burning mirrors to inflame the sails of an invading fleet. If the enemy has any straw roofs or wooden structures visible from outside the fortress, you can light them on fire.

The best part? Burning mirrors have the greatest range of any ancient weapon, since they merely require line-of-sight to attack, and they are easy to aim because they have a built-in indicator. Stick them on the tops of wooden towers five miles away.

The disadvantages are that burning mirrors only work if the fortress has some flammable buildings in it. A walled city is vulnerable to this method; a solid stone keep is not. It also may take quite hours to light an exposed object on fire, and burning mirrors only work if the weather is sunny.