Editing 23a:Siege engine

A '''siege engine''' in Dwarf Fortress is half building/half heavy weapon, and includes both the '''catapult''' and the '''ballista'''.  Both are formidable weapons of tremendous range (enough to reach from the mountain face to the map edge) and capable of dealing out horrendous damage.  A [[ballista arrow]] will possibly kill or cripple each and every common creature in its path indiscriminate of friend or foe, and can severely injure even a [[dragon]], and any enemy unlucky enough to be hit by a falling catapult stone is likewise in for a world of hurt (dwarves and tame [[creatures]] are magically immune to catapult ammo ''only'').

In order to build a siege engine, you first need to produce (at least) three catapult or ballista parts in the [[Siege workshop]]; catapults are made from any 3 '''catapult parts''', and ballistae are made from any 3 '''ballista parts'''.  All parts are made from any type of wood at a [[siege workshop]].  Beyond that, "parts" are generic - there are no particular "sub-types" of parts beyond the distinction between those for the two different engine types. The quality of the parts has no effect on the siege engine's operation, so there is no need to produce high quality parts except to augment your fortress's architecture value.

Once you have the parts, you may then build the respective siege engine like any other building, selecting the parts that you wish to construct that particular engine with.  The assembled siege engine is, effectively, a 3x3 building. It cannot be moved about other than by taking it down and re-assembling it at the new site. Siege engines do not impede movement, though, so you don't have to worry about building them in a corridor.

[[Ammo]] is destroyed upon impact.

* Both catapults and ballistae have narrow fields of fire - they will only shoot at creatures directly "in front" of them, and so cannot target anything off at an angle.  They can be turned 90 degrees, but that often will not solve the problem. Unskilled operators have trouble aiming perfectly straight, and their shots will randomly veer off to either side, resulting in a field of fire roughly 19 degrees across. Highly skilled operators are supposed to fire perfectly straight; due to a bug, however, this does not happen.

* [[Operator]]s are "civilians", and as such they will run in fear if enemy units come too close to them. "Too close" varies somewhat, but may be as far as 20 tiles.

'''Ballistae can and will kill anything in their path!'''  Ballista arrows appear to hit any units in any square that they pass through.  They are devastatingly dangerous weapons, and should never be used with friendlies anywhere in their cone of fire, including the space the ballista arrowhead occupies when loaded on the engine.  The shots appear to travel until they hit a wall or fly off the screen; the maximum range is about 150 tiles for an ordinary ballista. If the bolt passes through a [[tree]], the tree will be destroyed, and while the [[Elf|Elves]] will not count it against your [[Diplomat|tree cutting quota]], they '''will''' scold you for destroying the forests during their initial visit.

Though there is no benefit to making high-quality siege engine parts (aside from boosting your fortress's architecture value), high quality ammunition does significantly more damage. The only way of obtaining high-quality siege ammunition is to have them made by a trained engineer, and the only way to train an engineer is to make parts or ammunition. Assembling and disassembling siege engines does not train the [[siege engineer]] skill. Dwarves will occasionally produce masterpieces long before reaching [[Legendary]] skill level, but be prepared to waste hundreds of logs until then. Bringing an engineer to [[Experience|Proficient]] level (the highest you could buy when starting a new fortress) will take about 120 logs. Becoming Legendary requires the wood of 600 trees.

The operator skill significantly affects reload time. It can take several days for an unskilled dwarf to load a catapult, while a Legendary operator with nearby ammo will get several shots at a running enemy. Due to a bug, operator skill has no effect on accuracy - in fact, highly skilled operators can have '''reduced''' accuracy when firing catapults because the stone's arc height will be calculated based on a perfectly straight shot while the stone will still drift sideways.

Operators are best trained on catapults, as these require nothing but cheap stone for ammo. It is recommended to have a number of dedicated operators that will follow no other line of work, and enough catapults for all of them to play with. As they're often going for a drink or sleep, you may get along with three catapults for four operators, and even two pieces would go a long way. Since the dwarf must hold the heavy stone in his inventory during the entire loading procedure, dwarves that have increased their Strength can load catapults much more rapidly than others, making them good candidates for operator duty. You should start training early: it can take one year for an operator to become Proficient, and two more years until he finally reaches Legendary level; by then he will have spent 300 rounds.  

Ballistae hit any unit that the ballista arrow passes through.  This makes them an order of magnitude more effective in combat than catapults, which fire in an arc that hits only a few tiles per shot and is nearly useless against anything smaller than a troop of [[goblin]]s.  Also, ballista arrows fired through too many successive targets will be destroyed or lost.  The limit seems to be roughly 5-6 goblin-sized targets hit before the arrow is lost.

When the time comes, switch off all training engines and set all of the ones you'll be using to fire at will so the operators will be on-station; if some of them are currently not loaded, designate them to be disassembled to prevent your operators from loading the training weapons instead of firing the real ones.