Starting to get the hang of this game. Simply put, you don't play it like you'd play They Are Billions, you're meant to move around a lot, and get smart with your units positioning so that the enemy artillery is in range of your archers.
Bit too much micromanagement, though. It's very difficult to deal with said artillery, they kill most of your units in two hits, and instantly scare them (-50% movement speed and -50% damage).