Battlefield role
Long-range bombardment of fortifications and static positions — the unit that ends turtling.
Artillery is why the Industrial Age changes everything. The fortress lines that dominated three ages of play become targets — expensive, stationary targets — and every defensive plan on the map has to be rethought.
The gun’s own story is the same one as the ballista, at greater scale: immense influence, zero self-defense. Artillery decides where battles happen; escorts decide whether the artillery survives them.