On the adventure page, you can send your troops to Dungeons and Treasure Islands which leads them to a battle at last. Battles are automated turn-based. The player can set strategies and the formation of troops before the battle. Then watch the battle replay. Also, the user can set the target priority of units, in this case, the unit will attack the highest priority target in its range.
Units lose HP in battles and it takes time (depending on the level of Barracks) to recover their HP.
Damage and Resistance
Armor and Magic Resistance help units to get damaged less in battles.
How armor and magic resistance mitigate incoming magical or physical damage