Siege Rules
Attacking a castle is long and difficult. Mostly, it will involve waiting for the defenders to starve. The basic siege follows a pretty simple pattern, as far as the attacker is concerned.
Most besiegers of a castle follow a somewhat standard protocol.
Blockade the castle. This step is rather obvious and simple to accomplish. The attacking army needs to scout the surrounding territories and set up guards at key locations.
Dig in and fortify position. This includes constructing siege engines, defences, and securing supply lines.
Defences are usually earthworks and wood -- both are readily available from peasant homes surrounding the structure, so their cost is negligible. Construction of siege engines is highly important to attackers that wish to assail the walls, rather than starve out the defenders; it requires an
engineer to create siege engines. Supplies for the attacking army are the most important elements in this step. Without
them the attackers are in as bad a shape as the besieged. It is recommended that the attacker separate some units from the main group in order that they may secure the supply routes from possible attack.
Whittling down the defender. After supplies are secured and defences set up, the attackers generally attempt to breach the walls. Catapults, rams, sappers,
magic and any other means the commander can devise to accomplish this. The defenders should try to destroy everything they
can be it by nighttime sabotage, assassins sent over the walls, or their own catapults and magic. Siege engines are not always capable of breaching
walls as some are too well built or too big, or perhaps there simply aren’t enough nearby rocks to throw.
The Big Decision. The attacker, by now, has two options. If the engines are effective, he may attempt to assail the castle.
This is the most dangerous, but it is quick. The other option is to starve out the defenders. This depends on food and willpower, for both armies. The besieged will usually have about a few months worth of food stored up; without this, morale takes a
very steep drop. Willpower is important because the overwhelming boredom is horrible -- the attacker’s men want to actually
do something, and the defender’s men wake up every morning to see themselves surrounded. If the option taken by the attacker is to wait, then morale is a factor for both sides.
Ballistae: These are large, oversized crossbows that fire arrows about 6 feet long. Their primary usage is against opposing siege engines;
however some are modified to fire rocks, to be used as an anti-personnel weapon.
Catapult: This weapon is a mainstay of siege engines, and is used because it is effective. It typically hurls stones weighing about 60 pounds, although they have been known to be loaded with dead horses and other diseased ammunition in order to foment disease in the besieged castle, as well as lowering morale.
Trebuchet: This weapon is basically a sling, capable of hurling stones. Unlike the catapult, the trebuchet can throw rocks weighing up to 300 pounds, although not as far. This weapon is truly devastating to walls and structures.
Battering Ram: A big log to bash down doors and gates. Typically they will require protection of some kind, either from a siege tower or tortoise. The ram can also be mounted on a frame to increase ease of use, although this is only viable when attached to a larger structure.
Tortoise: This is a large mobile enclosed structure, typically 50 feet long, 20 feet wide, and 8 feet tall. From within its confines, sappers may work in relative safety, archers and mages may get into position, or a ram may be affixed in order to bash in a gate.
Siege Tower: A siege tower is a large, mobile tower, designed to make the attackers capable of marching over a wall and into a castle with great ease. A well-designed tower can hold its own siege engines within (catapults, rams, cranes, and ballistae). A large tower is about 80 feet tall, with a 40-foot by 40-foot base, and is capable of hosting up to 500 men. Fully loaded, a tower may weigh up to 300 tons. Keep in mind that moving one of these in a marsh is impossible.
Crane: Not normally a siege engine for attack (although they could be employed for that use), cranes are designed to pick up things, and then drop them. This tactic is very dangerous to most engines capable of being lifted, and especially ships. To be of
use the castle must have as many cranes as the enemy has siege towers.
A siege engine can whittle down a castle however the trick is to not have them destroyed by the enemy. Trebuchets are devastating, but their lack of range makes them viable targets for enemy catapults and ballistae inside the walls.
Ammunition for the siege engines is required. Supply routes must remain open. To this end, the attacker may wish to separate troops from his main army to act as escorts for the supply train. Troops separated in this manner will be considered to protect the train from enemy attacks, which will probably occur if the besieged has any allies of note.
Sappers are tremendously effective at their job, and are as valuable as siege engines, if not more so, although sappers may not ply their trade in a marsh. A sapper unit generally has three methods of attack.
Create a tunnel running from the safety of the rear of the attacker’s army, away from siege engine attacks, where they will attempt to tunnel under the foundation of the castle in order to undermine it. This is termed as “Burrowing to Collapse”.
Create a tunnel running underneath the enemy castle in order to create a secret entrance into the stores or dungeon of the castle, thereby allowing troops to enter the castle, bypassing the walls entirely. This is termed “Burrowing to Gain Entrance”.
Dig in underneath the wall or structure from next to the wall. This is essentially identical to option
1 except that this way is much, much faster, as well as much more dangerous. This is also termed “Burrowing to Collapse”.
Safe Set-up: In this set-up, the sappers start the tunnel from the safety of their own camp,
tunnelling towards the castle walls. This takes 6 weeks, minus two days for each
level of an engineer present. Each additional 2 sapping units reduces the time required by a week.
A sapping unit may Burrow to Gain Entrance. To burrow to gain entrance, follow the same procedure above for BURROWING TO COLLAPSE for time determination, as well as success chance. However, in this case, a success will allow the attacker to move in up to 300 troops, plus an additional 200 troops per week of extra time worked. Note that as this is a surprise attack, a Close Set-up is not viable; the castle defenders would surely become suspicious if they saw 300+ enemy troops running into a tortoise built for, say, 30.
Defence
Defending a castle is relatively easy. All you have to do is outlast your opponent; eventually, either reinforcements will arrive and break the siege, the attackers will run out of food, or morale gets so horrific the besiegers won’t have an army after all the deserters are accounted for. Of course, if that doesn’t work, you’ll get to watch your ancestral home burnt to the ground by a horde of mindless barbarians, or something of the sort.
Generally, you can expect the attacking army to have roughly three to four times as many troops as you. Get used to that. However, killing them is not your objective. The objective of the troops manning the walls is to protect the walls, although this generally means killing attackers. If a wall falls, then the castle is just a big box that you’re going to die in.
Sappers constitute a great threat against a castle. If possible, every castle should have a moat to defend against sappers, although this is sometimes an unrealistic goal (such as in a desert). In any case, the castle defenders should be prepared to deal with sappers. The easiest method is by Hoarding, described above. However, hoarding only deters those sappers who are against the wall. Sappers who work from behind their own lines are far more dangerous.
Once sappers have been spotted, stopping them is the tricky part. Either the sappers are trying to gain entrance to the castle, or they are attempting to collapse the walls. To defend against entrance, the defenders may either wait readily for the sappers, or go out to meet them, underground. Obviously, if the sappers are trying to collapse a wall, then waiting is a bad thing to do. Once the entrance location has been determined (or the wall to be collapsed, as the case may be), the course of action becomes much clearer.
A defending commander may order his sappers to intercept the enemy sappers. The enemy commander may assign units to aid in the attack.
The defending commander must deal with the constant barrage of rocks and disease. Failure to bolster the spirit of the defenders will result in a dramatic decrease in the will to fight.
How well do sieges work in a magic rich world?
Beyond even the battlefield-changing ramifications of flight though, there are some things to worry about that aren't present even in modern warfare: teleportation, insubstantiality, and high-level heroes. These grant the ability to simply ignore battlelines and insert a soldier who can single-handedly take down a regiment of common troops into the heart of enemy territory. Needless to say this effectively negates any and all perimeter based defences. If teleporting is blocked just replace someone with a doppelganger, simulacra or clone. Get them to let your troops in past the defences, tell you the magic words to open the spell barriers, whatever. Then there's the big rock approach. If you can't attack them directly, try levitating giant rocks overhead and letting them go. If it doesn't do enough damage, repeat with a bigger rock. If absolutely necessary bury the entire fortress under a mountain; they may still be alive in there, but you can go on and loot their lands while they try and dig themselves out. Ritual magic is a big boost here; if your game system lets multiple wizards cooperate to throw really long, powerful spells, then whoever has the best team of ritual mages will probably win the siege.
The battlefield then becomes almost exclusively
one of magic. Anti-magic fields need to ring any and all defensive positions.
Scrying effects keep watch over every corridor. Keeps will likely be discarded
entirely in favour of restricted-access planar redoubts or at the very least
dungeons. Dungeons can be restricted to a single entry point, which can be armoured
by hundreds of feet of packed earth separating it from the surface. This depth
will prevent a new entry from being blasted open without great difficulty. In
addition the nature of a dungeon, with individual corridors separated by yards
of solid stone or earth makes teleportation without extensive knowledge of where
to go a risky proposition at best.
This shift in battle strategy makes information more valuable than troops.
Troops are mere meat in a world of fireballs and invisibility. The command word
to access a pocket plane though or a map pinpointing a safe teleportation
location within a dungeon will become the true treasures of the land. After all
this is a world in which anyone can kill a couple of goblins and become a force
to be reckoned with, capable of tearing down a conventional fortress brick by
brick. Therefore everyone is a potential threat, but at the same time everyone
is potentially replaceable.