One of the things that's frustrated me as a player with the campaign AI is when two opposing armies are travelling past each other (within visual/scouting distance, by not passing within engagement range) and continue without much thought to the other, only later for one to turn around to defend once the other reached it's destination and started a siege.
I struggle with it because it feels wrong to watch two armies walk past each other, knowing the other is on it's way to kill/fight some of their own people. If one army is significantly weaker than the other, it makes sense it would choose not to engage, and indeed it could be seen as a tactic to siege a nearby settlement of the enemy to force their army to return and defend. In practice, I don't feel like the AI is doing it for that reason, and continues on a path toward city/settlement that they won't reach before the enemy reaches its target -- and so the army turns around all too late, when it feels like it should have known in advance (scouts, spies, etc. whatever to justify why our mouse cursor reveals intent).
I struggle with it because it feels wrong to watch two armies walk past each other, knowing the other is on it's way to kill/fight some of their own people. If one army is significantly weaker than the other, it makes sense it would choose not to engage, and indeed it could be seen as a tactic to siege a nearby settlement of the enemy to force their army to return and defend. In practice, I don't feel like the AI is doing it for that reason, and continues on a path toward city/settlement that they won't reach before the enemy reaches its target -- and so the army turns around all too late, when it feels like it should have known in advance (scouts, spies, etc. whatever to justify why our mouse cursor reveals intent).