Catapult

Summary
Catapults are an artillery brigade available to the Greek faction group in the late game. They are the only artillery in-game, being a special ranged brigade that costs wood rather than recruits and can be created in camps as well as cities.

"A small mobile arrow-firing artillery piece used against infantry rather than fortifications."

- In-game Description

History
Early ballista-style catapults such as the Oxybeles were first developed by the Greeks of Italy, with the first real examples perhaps being developed in Syrakousai around 400 BC. They would quickly spread across the Greek world from there. Siege engines were still in their infancy, however, and the Greeks and Romans would continue to develop better types of catapults over the course of the next few centuries.

Tactics
Catapults have a relatively low missile damage output as a brigade (though a very high damage per individual unit), a very slow movement speed and no capacity for melee combat, making it seem hard to justify their high gold cost and long time to recruit.

Their true advantage lies in the fact that they cost wood rather than recruits to create, and can even be created in camps as opposed to only in cities. This allows the player to add additional missile support to their armies on the fly, so long as the army's current camp has supply lines providing it with wood.