Would Your Ships Even Fight?
The first thing to consider is whether or not the admirals of your setting would even want to fight enemy ships at all. Sea battles with this tech level are incredibly unpredictable, and it’s easy to lose most of your fleet from bad weather alone. It’s more than plausible that your warships would be entirely focused on moving soldiers from one landmass to another.
If that sounds like the coward’s way out, consider that it was the preferred tactic of the famed Viking longships. These mighty vessels weren’t built with combat in mind. They were actually at a disadvantage when coming up against the much larger ships of southern Europe. Instead of combat, the longship’s strength and flexibility meant they could sail in nearly all weather, and their speed let them outmaneuver any craft they might encounter.
This strategy is obviously useful for raiding, but it pays dividends in war as well. If you can get your entire invasion force onto the enemy’s shores without a fight, any naval conflict could become irrelevant. Once you control the ports, your enemy’s ships will either have to retreat elsewhere or be quickly starved out. This approach can be effective in any era, but it’s especially potent before gunpowder, when ships had very little ability to attack land-bound targets.
Of course, naval battles did happen in pre-gunpowder days, so they can happen in your setting too. It’s just important to understand the factors involved. For one thing, the Viking approach requires that one side’s ships be significantly faster than the other’s, and its historical success declined as other European powers adopted the longship design. A larger fleet also has more difficulty avoiding the enemy, and its list of potential landing zones is shorter too. A lot of naval battles have been fought to stop an enemy from landing soldiers on a specific beach.
Once you’ve figured out if your story has the factors that would lead to a naval battle in the first place, it’s time to consider the tactics available.
Before the invention of cannons, ramming was one of the only ways to reliably sink another ship. In principle, ramming is simple: poke a hole in the other boat with your boat. In practice, it’s a lot more complicated. First, you need the ram itself. This is usually a blunt protrusion of a heavy metal like bronze attached to the front of the ship. Rams weren’t usually sharp, since that increased the chances of getting stuck, and if you get stuck, then both ships are going down.* The ram also needs to be attached to a strong keel; otherwise, the ship will crumple like a paper bag on impact, and that’s not great for morale.
Once you have the basic equipment, you need a set of extremely skilled officers and crew. Ramming attacks need to be aimed at precise angles, or they’ll just deflect without causing any damage. The pilot and captain need to be on their game, of course, but so do the rowers. Ramming ships will almost always be powered by oars, not only because the wind is often unreliable but also because repeated collisions are a great way to damage your own delicate masts and rigging. If the oars aren’t in perfect sync while ramming, it can throw off the ship’s aim and make the attack useless.
Now, we come to the tactics of ramming. It’s unlikely that two ships will just rush at each other like jousting knights of the sea, as that’s just mutually assured destruction. Basic physics tells us that the best ramming attack is to strike the enemy amidships at a perpendicular angle, but that can often be too successful, as it drives the ram so far into the other ship that it’s likely to get stuck. Instead, the best place to strike is usually the stern at an angle. This maximizes the chances of inflicting a fatal blow without getting stuck, like so:
Alternatively, a captain might aim to sheer off an enemy’s oars rather than strike the hull. Your ships are likely to carry extra oars as a contingency, turning the fight into a battle of oar attrition.
As you can imagine, such complex tactics mean that a ramming duel will involve a lot of maneuvering as the two ships circle around each other, their captains constantly looking for an opening. This can get really chaotic in a fleet engagement, so victory will often rest with whichever admiral can best coordinate their ships. Common tactics might include sending a force of ships to encircle the enemy from the flank or using a line of ships like a spear to break through the enemy’s line.
One thing ramming ships won’t do if they can help it is board each other. The whole point of the ram is to sink an enemy in one quick strike, not get bogged down in a protracted melee. Ramming ships are also unlikely to carry many soldiers, as they need all the space they can get for rowers. The only time you’ll see boarding between two ram-focused ships is if one of them gets stuck in the other. That said, boarding is also an important tactic, so let’s take a look at that.
Ramming is complex and difficult, requiring a skilled crew and more than a little luck. By contrast, boarding is relatively simple. Just take your land soldiers and put them on boats, then let them do what they do best!
While ramming ships will usually be sleek and fairly low to the water, in boarding the tallest ship is at a distinct advantage. Having the high ground means that your crew can rain missiles down on the enemy from a position of safety, and then descend to the other ship’s deck with gravity’s aid. Meanwhile, anyone who gets the bright idea to counter-board has to climb up your own ship’s high sides.
The height advantage is so important that, historically, ships were often built with fortified towers on the deck to give some extra altitude. In the Middle Ages, these towers were often known as the forecastle and aftercastle, as they resembled actual castles. The downside to such nautical fortifications is that they raise a ship’s center of gravity, making it unstable and likely to capsize in rough weather. If your sailors aren’t super enthused by that idea, they might take a page from the ancient Mediterranean playbook and set up temporary towers before a battle. The height advantage is smaller, but putting the towers away after each battle means the ship is less likely to sink between fights.
The actual process of boarding is straightforward. The two ships come alongside and are usually tied together with ropes and grappling hooks. Then the two crews have at each other much like they would in a land battle, with the main difference being that the shifting decks make everything a little more chaotic. Spears and other polearms are often used in the opening clash, and after that it’s close-in work with short swords, hatchets, clubs, and any other weapons at hand. Crews will probably put down sand or straw to soak up the blood so their ship doesn’t turn into a slip and slide, and they will absolutely wear armor if they can get it. The risk of drowning is nothing compared to the risk of being caught in a fracas with no protection.
While this all sounds good, there are a few disadvantages to boarding as a battle tactic. For one thing, ships loaded down with marines will be slower, and a lighter enemy could simply escape if they have no pressing need to fight. For another, boarding is a tactic of attrition. You’ll always lose some soldiers in a boarding action, even when you win. That’s why ramming is so attractive: it lets you sink the enemy without taking your own losses.
When a ramming ship fights a boarding ship, things get interesting. The boarding ship will always win if it can close to melee range, as a ship focused on ramming simply doesn’t carry that many marines. On the other hand, the ramming ship is likely to be faster, since it has more rowers, and can possibly sink the boarding ship without ever giving it a chance to fight. To avoid this fate, the boarding ship might use something like the Roman corvus, a mobile bridge that sunk spikes into the enemy ship and held it in place. The weight of these bridges also made ships unstable, but it was well worth the trade.
So if ramming is difficult and boarding is costly, why not just stand off at a distance and pelt your enemy into submission with arrows, sling stones, bolts, javelins, and a well-placed ax or two? Your ships will absolutely make use of these weapons. If they follow historical precedent, they’ll even have pre-gunpowder artillery like ballistae and catapults on board.
However, none of these weapons will be used to sink enemy vessels. It’s simply not feasible for personal weapons like bows and slings to damage a ship, and even the artillery pieces will usually be too small to inflict a killing blow. It is possible for ships to carry larger siege weapons, but these will be for attacking targets on land, as a trebuchet is simply too slow and awkward to hit a moving ship.
None of this is to say that pre-gunpowder projectiles aren’t important in naval warfare. On the contrary, they allow your ships to score an early advantage over the enemy before the ramming or boarding starts. A well-placed volley of arrows can kill both rowers and marines, making it that much easier to outrun or overwhelm the enemy ship. Naval artillery can also be used against enemy crews with devastating effect, or it can target the rigging of sail-powered vessels, turning them into lumbering hulks.
Ships designed for missile weapons benefit a lot from extra height, as it gives their projectiles more range and makes shooting back at them harder. This is one reason your boarding-focused ships will sport a lot more archers than the ramming-focused ones. While melee fighters will always be necessary, a good barrage from the forecastle can often break the enemy’s resistance, leaving the marines with only a little mopping up to do.
Ramming ships, on the other hand, may carry a few archers, but for the most part, they just don’t have the space. Every person not working the oars is slowing the ship down, and that’s not something a ship can afford if its captain means to ram.
In any pre-gunpowder story, ships are almost guaranteed to be made out of wood. Wood is famously flammable, especially once it’s sealed with tar and resin, so it only makes sense for the navies of your world to use fire as a weapon at sea.
The simplest way to employ fire as a weapon is by attaching something flammable to an arrow and lighting it up. Fun fact: this is the only situation in which you might describe a character “firing” an arrow instead of “loosing” one. These fire arrows are great for sowing chaos and confusion among the enemy ranks, as humans are notoriously frightened by fire, but they’re unlikely to burn a ship down. It’s simply too easy to put these small bits of flame out before they spread. Of course, if someone just happens to leave a barrel of oil out on deck, that’s a different matter.
The next step up is the fire ship, and it’s exactly what it sounds like. You stuff a ship full of flammables, light it up, and push it toward the enemy. Nothing puts the fear of Poseidon into sailors like a flaming hulk bearing down on them. Despite their terrifying nature, fire ships aren’t primarily employed to cause damage. You can’t put any crew on them, so it’s almost always possible for the enemy to maneuver out of the way. Instead, fire ships are used to break up opposing formations, as enemy captains scatter in a frantic dash to get out of the way, leaving the perfect opening to exploit. The only time fire ships are likely to light something on fire is when the enemy is packed close together, like in a crowded harbor.
The obvious downside to fire ships is that you have to light your own ships on fire. That’s why fire ships are usually made from whatever vessels aren’t fit for the main line of battle, but even so, no navy will have an unlimited supply. It’s also possible for fire ships to rebound on their own side if the wind or currents shift, which makes for an interesting battle indeed.
Finally, we reach the undisputed king of pre-gunpowder weaponry: chemical fire. This is any substance specifically designed for flammable properties, with a focus on burning hotter and being hard to put out. The most famous historical example is Greek Fire, first deployed by the Byzantine navy in the seventh century. We don’t know exactly what Greek Fire was made of, but from accounts of the period, we can guess that it was petroleum based, likely with other additives.
Whatever the exact mixture of your setting’s chemical fire, is will almost certainly be a devastating weapon, as it’s the only ranged weapon available that can actually sink enemy ships. It burns hot enough to easily spread over an entire vessel, and it can’t be extinguished with water. Only sand or a chemical counteragent like vinegar will do the job. The most direct method is to simply pump the fuel through a siphon and spray it at whomever you don’t like, because fantasy stories don’t have enough flamethrowers in them. This method’s range is only a few dozen meters at best, but that’s more than enough. It’s also possible to pour chemical fire into grenades and deliver it that way.
Needless to say, chemical fire is an exceptionally dangerous weapon to use. Any cracks in the joins between fuel tank, pump, and nozzle can leak out fumes that will make the whole thing explode. Several sources insist that the Byzantines heated Greek Fire over a brazier before deploying it, either to pressurize it or to better mix the ingredients, which would have made it even more dangerous. Even if everything works perfectly, a sudden change in the wind can send liquid fire back in the direction from which it came.
Despite the drawbacks, chemical fire is the last word in pre-gunpowder naval combat. There’s simply no way for the enemy to fight back unless they also have chemical fire. In that case, fleet engagements will resemble funeral pyres as much as battles.
As with most historical topics, it’s possible to go far deeper with the details of naval combat. You can dive into the differences between the trireme and the dromon or spend hours researching the precise effects of wind changes in a battle. But for most stories, a general understanding is all you need, since your goal is to help the reader imagine what naval combat is like rather than drown them in details.
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