Siege weapons or engines are large weapons, including catapults, the trebuchet, ballista, and other large scale weapons.
They were commonly used as period artillery, and against stationary targets, like castles and other fortifications. Siege weapons were only occasionally used in an anti-personnel capacity.
Siege Weapons in the SCA
In the SCA, siege weapons can be used in wars. If a fighter is struck by a projectile from a siege weapon then the convention is that they are dead. Not even plate armour is proof.
Engineers operate siege weapons. If the weapon misfires or is struck by another weapon's projectiles then the weapon is regarded as destroyed. If all the engineers are killed by any means, then the siege weapon can be captured and used by the opposing force.