Each player participating in battle rolls 1 die and adds the number of Troops/Fleets he has in the combat zone.
If the battle takes place on an isle where one or more Fortresses have been built, the defender adds «1» to his die value for each Fortress.
If the battle takes place on a sea space adjacent to an isle (or isles) where the defender has built one or more Ports, the defender adds «1» to his die value for each Port.
The player who has the lowest result loses the first assault. He removes a Troop / Fleet from the battle and places it in his reserve, in front of his screen. If the result is a tie, both players lose a Troop / Fleet (see note at the bottom right corner of this page).
If both combatants still have Troops / Fleets, the defender can decide to retreat. If he does not (or if he cannot), the attacker can also retreat. If neither of the players retreat, a new assault takes place (see step 1).
These steps are repeated until only one player is left in the combat zone. That player takes control of the isle or the sea space in which battle occurred. If it was an isle, the winner also gets all buildings found on the isle.
Retreating during a land-based battle
If one of the players wants to abandon combat, he must bring his Troops back to an isle belonging to him and linked by Fleets to the one where battle occurred. If these conditions are not met, the Troops cannot retreat.
Retreating during a sea-faring battle
If one of the players wants to abandon combat, he must move his Fleets to an empty adjacent space or one he controls. If no space matches these requirements, the Fleets cannot retreat.