Pay attention to battle previews
In combat, when you direct a unit to move toward an enemy, you will get a preview of what the outcome of the battle will be. This preview appears again when you are about to enter combat, which will inform you of how much damage both sides will take. If you deal more damage, it counts as a victory, putting the enemy in a weakened state where you get to strike first in the next battle against them. When two units are about to battle, you cannot run away, but you can swap with a nearby unit. You also have the option to use items, so if you have damage- or defense-boosting items, you can use them to sway the outcome in your favor.
