I am facing a conundrum. You see, my world has magic, but this magic is very restricted and has great limitations. As consequence of these limitations, they never got into metalwork, developing no cannons, but their magically enhanced woodwork allowed for far better wood than anything medieval. Soldiers operating the wooden siege weapons also have ability to give their siege weapon a small boost during firing, although it isn't too large.

My question is, how much would I really have to up the specs of balistae/catapults to make them viable weapons for ship of the line tactics?


Medieval level civilizations did discover such thing as medieval incendiary weapons. Greek flame, white phosphorus, etc. are in regular use. They do have gunpowder, but wooden cannons are not very useful, since their effect can't be magically enhanced, and are mostly seen as nobility entertainment with little military value, much less naval aplication.

There are no magic explosives. At least not in the hands of pre-magic-industrial societies.

Archery is stronger (and logically, also has higher range), because of soldiers being able to magically increase their physical strength, as well as better materials for bows and arrows and more skilled woodwork.

Combat mages are restricted to throwing flame at enemies and don't really have any attack with range over 100 m, or 150 m with help of disposable magic tools.

I mean having bolt and stone throwing ships of line is a really cool image, but I need to make sure whether it would be practical in my world, or whether it would require too much magic for it to be viable in my setting.

  • 1
    $\begingroup$ This kind of pre-gunpower artillery was never used aboard ships (never = very rarely, history being rather fond of exceptions to any rule). The problem is that you cannot really aim them from a ship in continuous 3D motion towards another ship in continuous 3D motion. Even cannon were of rather dubious utility until the advent of the true ship of the line, mounting dozens of cannon in each broadside. In pre-gunpowder days, naval ships sought to ram each other (and were fitted with special-purpose rams), or to come alongside each other and let their marines sort it out with melee weapons. $\endgroup$
    – AlexP
    Nov 29, 2019 at 18:23
  • 1
    $\begingroup$ Ad: Introducing kraken from South East Asia, it is cute and learn fast. You can teach it tricks such as fetch.... Mother sold separately. $\endgroup$
    – user6760
    Nov 29, 2019 at 23:36

7 Answers 7


The main issue for having ballista/catapults on a ship is given by their size and mass.

Considering the usual design of a medieval ship, having a large mass high above the center of mass of the ship would have unbalanced the whole assembly, especially upon launching the projectile with the involved jolt. If I remember correctly certain ships could not fire their cannons all together on the very purpose of not tipping over.

If you want ballista/catapults to be viable in your system, they have to be small and light enough to be hosted on the deck of a ship without unbalancing the ship, not interfere too much with the sails, not have a large jolt.

  • $\begingroup$ what about cannons? They were fairly heavy? $\endgroup$
    – Slarty
    Nov 29, 2019 at 13:28
  • $\begingroup$ @Slarty, yes, but they could be fired from below the deck (so closer to the center of mass) and were not fired all together. $\endgroup$
    – L.Dutch
    Nov 29, 2019 at 13:29
  • $\begingroup$ yes I suppose I'm thinking of ships of the line from the 1800's and this is earlier... mind you the Roman scorpion might work well as it was not that heavy and had a good range. $\endgroup$
    – Slarty
    Nov 29, 2019 at 13:35
  • 1
    $\begingroup$ Why couldn't ballistae or scorpions be mounted below deck just like cannons? $\endgroup$
    – Ryan_L
    Nov 30, 2019 at 6:20

There's not really a point when there's a better strategy

I mean, you could, theoretically. But why would you want to do that when you could win the battle with a handful of small ships? In your specifications, you mention that there's Greek fire and white phosphorous available. Both of those are nasty. Greek fire, from reports, basically didn't go out even underwater, burned a brilliant green color, and was very, very lethal. The modern day equivalent to this seems to be thermite, which is not possible to extinguish using conventional methods. It is bad.

And white phosphorous is worse. Much worse. Because, see, it violently reacts with water, is also difficult to put out, and produces vapors which will kill people. (It's like 1/30th as bad as mustard gas, but will still incapacitate anyone nearby, and they have nowhere to run on a ship. Not to mention that they still need to man the ship anyways. A disabled ship's crew is a dead ship's crew.) Using white phosphorous for any other purpose other than smokescreen in modern combat is considered chemical warfare, and thus banned by international law. Essentially, if you managed to start either a Greek fire or a white phosphorous fire on an opposing ship, they would be dead.

The theory behind 'ship of line' is to have a full broadside, because it's the amount of hits when you're dealing with cannons. It's basically a double-edged sword - true, you show the full body of your ship as a target, but you also bring all your guns to bear. But, supposed you manage to have a modified catapult flinging the stuff. At that point, you want to approach from the ship's bow, to present as little of a profile as possible. Combat wouldn't be 'line of ship', it'd be two navies making charges at each other. If either side dares to show a full broadside, they'd take a direct hit from the catapults and be destroyed, even if they did land a blow.


This is far more effective than ballistas and catapults at disabling an enemy ship. Simply put the damage from ballistas is pitiful against structures, the ammunition is simply too light and too fragile to cause large amounts of damage, added to which it sticks in whatever hole it creates. Catapults are a touch better, they have a heavier, less fragile payload but have shorter range and require an arced trajectory. This makes them harder to hit moving targets and would still struggle to do significant damage, especially if your world magically enhances its woodworking.

Some better alternatives from ancient times:

Ancient maritime warfare often involved teams of rowers and a solid brass ram at the front of the ship. Ramming an enemy ship as opposed to ballista or catapult attacks you have an immense amount of weight behind the impact that can split an enemy's hull in one strike and leave them to sink in short order. This does require practiced rowers that can keep up the pace without their oars interfering with each other.

Some ancient civilizations that were less used to maritime war and more practiced with land warfare such as the Romans created a long bridge-like structure that could be deployed from their ship to an enemy ship. The bridge had iron spikes on the end and hooks that would bite into enemy decks and railings allowing their soldiers more familiar person to person fighting than precision rowing.

Archer deck
Further other ancient ships would have an archer platform above the main deck where you would simply have as many archers as available shoot from. Because the archery deck was fashioned similar to a wooden crenelated castle wall it offered more protection than firing from the main deck and left room for rowers and storage on the main deck. This type of ship however had to be very careful of ramming vessels as the weight of the archer deck made the hull more vulnerable.

One last idea that was more theorized and never weaponized was the Syrian torpedo. This was a device that skimmed across the water carrying fire, unfortunately not much else is known. Your world has gunpowder however which means a clever person could create weak fireworks and rockets which you could attach to a small floating platform carrying white phosphorous or Greek fire that you would propel towards the enemy.

Another idea that could be more comparable to a ship of the line and utilizing gunpowder rockets, you could have your ships armed with panels of Korean Hwachas, basically a series of tubes loaded with rocket propelled arrows. While this approach would have minimal effect on the structural integrity of an enemy ship it could devastate its crew and make it vulnerable to boarding actions.


Your suggestion of using ballistae or catapults presents two issues : Logistics and Damage.

On logistics first :

As others have pointed out, ballistae and catapults are big engines that take up a lot of space. While putting 1 or 2 on a ship isn't a problem (and is a think historical), you're going to have a lot of trouble putting enough of them on a ship's deck to deliver a broadside/of-the-line fire. That's why cannons were so practical : they're essentially metal tubes, and their firepower compared to their size is great.

There are however ideas for traditional weapons you could feasibly puton ships that would help with your space problem :

Roman-style ballista enter image description here This is a ballista (there is a more specific name but it escapes me) that was used on battlefields to fire javelin-sized bolts at enemy formations. They are small, operated by 2/3 soldiers, and have a reasonably high rate of fire.

You could put quite a lot of those on the deck of a ship and thus achieve a "rain-down" effect making use of their rate of fire, although they would be less destructive than bigger devices.

But thanks to genius Leonardo da Vinci, we also have catapult designs that are more compact than traditional catapults : enter image description here This is da Vinci's catapult concept. As you can see, its main feature is that contrary to a normal ballista, the 'bows' it uses for tension are place vertically, not horizontally. This means that you could place several of these catapults much close together than you could normal ballistas, for the same (theoretical) destructive power.

Now it would seem that we solved the logistics problem. However, the bigger and much more important problem is damage.

On damage :

Cannons, even in their primitive stage, have significantly more potential power against structures than more traditional siege weapons. Even with several of them and magical enhancement, it's highly dubious that a ballista bolt would be able to penetrate or in any case fly much futher than a warship's hull. Ballistae are primarily anti-personel weapons, they do little structural damage.

While catapults are more powerful, they still present the disadvantage of being fairly inaccurate, not least because they fire in an arc. Even with the help of magic, I doubt you could really improve that.

So it would seem that ships in your universe, especially using that reinforced wood, would be mostly safe from catapult/ballistae fire (except for incendiary projectiles). In that sense, of-the-line formations that use broadside firing do not make much sense.

Hence, here is my suggestion in how ship structures should change to account for that :

Your ships are built to be as tough as possible. At the same time, they are built up high or have an elevated part (much like a ship's "castle" in real life") on which as many archers as possible can take place. The ship's tactic, instead of bombarding the enemy ships, is to get close to them, and from their high groud rain down arrows on the enemy crews.

Up close, these ships could wreak havoc on enemy crews and board their ships.

The alternative is that you develop ammunition, maybe magic ammunition, that is primarily fire-based to set fire to enemy ships with your catapults.

  • $\begingroup$ Thet's "roman balista" is not a balista at all - it doesn't use bows tension, but torque from torsion joint (it's like two small catapults working together). So no wood enhancment would benefit for it. And it (called scorpion) was better in power/mobility/accuracy than any medeval field artillery, including fist gunpowder cannons. $\endgroup$
    – ksbes
    Nov 29, 2019 at 14:00
  • $\begingroup$ @ksbes Like I said, it had a higher rate of fire and was great against infrantry, now what about structural damage ? Ships are made of wood, not people, and their crew are often protected by the structure. To defeat a ship, you need to damage it, and a scorpion can't do that. $\endgroup$
    – Kaloyan
    Nov 29, 2019 at 14:57

Improve the Accuracy

This was the worst drawback of a catapult. Catapults could vaguely project a flaming ball, or rotting cattle at a city, but could scarcely aim it at anything intentionally. At sea, this becomes so much more pronounced because of the higher chance of not hitting anything, and the lack of an explosion due to the water would mean very little chance of fragmentation/splash damage. If you could make magically stronger wood, then you could technically make a stone-throwing ballista that could either impart a kind of rifling effect on the projectile, and at a higher speed (higher strength wood -> more tension can be imparted) this accuracy would improve.

You mentioned wooden cannons. Some of the first cannons in the far east were made of wood. These didn't garner widespread success, however, because they were prone to exploding, as the pressures required to fire the projectile would prove higher than the wood could handle. If you have magically-altered wood that is significantly stronger, this would be more feasible.


I don’t think you would even need magic (although obviously if you want to use it why not…). But in a world where there was no metal and no guns catapults and similar weapons would rule supreme.

Close range bows and small bolt shooting engines like the Roman scorpions, with a range of 400+ m a volly of those firing flamming arrows would be quite effective. Although at long range they were not that accurate, they wouldn,t need to be if firing at a lots of sails.

At long range much larger catapults that can fire rocks or burning pots of pitch and sulphur/ Fire attack on wooden ships can be devastating. The ship with the largest number of large catapults probably has an advantage in being able to set ablaze an enemy before being hit itself. So there might be an arms race to see who could install the largest number of catapults. The pitch and sulphur would be ignited just before launch.

They would also need to take precautions such as washing the decks and having water ready to put out fires.


There's no real reason you couldn't have a ship-of-the-line, and instead of a cannon broadside you have ballistae.

This comes with a few problems. First, ballistae are pretty wide compared to cannons. This means you can fit fewer ballistae than cannons in a given length of ship. So your broadside will be a lot lighter. Second, you said they have limited or no metalworking. You're just not going to be able to throw anything heavy or hard enough to do serious damage to a ship-of-the-line. I mean, some of the small cannons didn't always penetrate in real life, meaning I don't think your ballistae stand much of a chance like that. Third, I think salt water will do a real number on your ballistae. Wood swells when it gets wet. It seems like you would need to keep them unstrung until it's time for battle, or else the swelling and shrinking against the string will put a lot of wear-and-tear on them.

But I don't think it's all bad. Ballistae could be remarkably accurate over surprising distances; there are Roman sources bragging about picking off specific people beyond bow range with their scorpions, and a ballistae isn't much different. You also don't necessarily need to penetrate a ship's hull to destroy it. You say you have Greek Fire and White Phosphorus; fill ceramic pots with that stuff and aim for the rigging. Either they'll break on the rigging and set the sails alight, or they'll fall to the deck, break, and set that alight. Maybe if your crews get good enough they could aim for the enemy's ballistae ports to start a fire below deck.

One big change that's neither good nor bad that I foresee is that very few ships will be captured. In real life, ships-of-the-line were somewhat frequently boarded and captured, rather than sunk. But with everyone throwing napalm at each other, it seems unlikely. Would you want to get close to a ship that could set yours on fire? Would you want to board a ship that you already set on fire?


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .