The signals to rebellion start slow: you pester and annoy the enemy to let them know they have tread on the wrong turf. You try to inform them, then you try to concede points for shared ground. Once the enemy has decided that your advancements and ground meeting are to their advantage, and continue to gain ground is what we identify as skirmishes and battle starts. You ambush, you destroy logistical routes, you make it difficult for the enemy perceive that this ground is worthwhile.
At what point do you fire the cannons? At what point does the normally docile rest of society join you to arm your rebellious battlements?
I think you are witnessing the populous arming their cannons. You can object, but you can't object that the enemy is closer than ever.