Normally, in a war the parties involved rally their armies, assemble them, and then make those armies face each other in big battles.
That's why the excommunication works. With the goddess awake, it's just a matter of having a big enough number of people able to cast the area version of the spell to convene before said battles.
They then cast the spell over the to-be-defeated army, and what follows is a massacre.
I thought that fighting a guerrilla war was the way to fight while underpowered by the excommunication. Instead, it was actually a way to avoid excommunication.
I mean, some of our soldiers were excommunicated. About one-third of the main army and a couple dozen of the hidden army. It wasn't nearly enough to break our fighting power.
We also directly threatened the Church, which is something nobody did before. With the goddess silent, the high command that lived in East Rising had to flee.
And we killed almost all the priests who were working with the Blessed army.