Siege Artillery Explained
Make sure you move the physical unit into the battlefield where you intend to use it. After a battle starts that has siege artillery present you will be able to choose how many days to bombard enemy lines in the deployment phase, and use single directed barrages while in battle.
How to Use Siege Artillery
The 4th button along in the preplanning is your siege planning. so you have buttons for:
On the siege tab you use the ‘plus’ button to adds days of siege artillery, e.g. will cost a lot of supply and will have a chance (displayed) to destroy trenches etc. IT then happens as the battle starts, you will see some flashes on the enemy lines and messages for what has been destroyed.
During the battle itself, the siege tab gun tab is still there, you can a pile of supply for an in game strike, that also has a massive recycle delay.
You really need quite a few siege batteries for it to be really good, and the extra techs that follow it in the economy group. If you have those techs, a few siege batteries and a fair bit of supply then it is pretty good.