Haven – "Everything is mixed up, truth and falsehood" [Campaign 3 – Mission 2]

I don't know how to describe it (maybe I was just lucky), but at the beginning of the mission, all the barons had a huge army, and when I hovered over them, it showed a red skull indicating a threat. But after I captured the Necropolis, then the purple castle, and continued towards the lower-left castle, during its capture, a hero came from another bridge, captured the former Necropolis, and ran upwards towards my Fortress, capturing it as well. I quickly returned to recapture the castle, and when I caught and killed that hero, I noticed that he had left almost his entire army in the Fortress. That's how, by not letting anyone get close to that Fortress, I deprived the enemy of its main army and quickly captured the rest.