The result of a battle is affected by the troop type, active Boosts, the Hero's and Inquisitor's bonuses, Skills, Doctrines, Reputations, Townscapes, conducted Studies, and so on.

At the time of the battle, some of the bonuses may have expired, for example, the bonuses from a Boost or a Reputation. Alternatively, the wrong piece of equipment may have been equipped on your Hero or an Inquisitor accidentally.