If some but not all of the combatants are aware of their opponents, a surprise round happens before regular rounds begin. The combatants who are aware of the opponents can act in the surprise round, so they roll for initiative. Combatants who were unaware do not get to act in the surprise round. If no one or everyone starts the battle aware, there is no surprise round. Combatants who have not yet rolled initiative do so.
Combatants act in initiative order.
When everyone has had a turn, the combatant with the highest initiative acts again, and steps 4 and 5 repeat until combat ends. A combatant threatens the area into which it can make a melee attack, even when it is not a combatant's action. An enemy that takes certain actions while in a threatened area may provoke an attack of opportunity from a combatant. A combatant normally threatens all adjacent spaces. If a combatant's entire move for the round is 5 feet the 5 foot move does not provoke an attack of opportunity.