I have a situation in a game where an artillery battery has an enemy unit in the open in it's fire zone. On it's left side the fire zone is occupied very slightly by a town base. The town base only obscures a single artillery base so that would mean that the remaining artillery bases could fire as normal on the enemy unit in the open.
However, the town base is occupied by an enemy unit. The range is within the canister zone. Does this mean that the unit in the town base (partial target) becomes the priority target for the artillery. My reading says yes but my opponent disagrees.
What is the correct procedure?