The new battle systems works in the following way, by information from the developers of the game in the official forums and by experts that tested the new system.
All combat in KOC is round based. When you attack, all of your attacking troops arrive at the city at the same time. As soon as the first attacking or defending troop is within range (usually the one with the longest range like Cats or Ballista) Combat begins. During the first round of combat, all troops within range fire. Simultaneously, both the attacking and defending troops begin to advance toward their foe at their various speeds. The defenders leave the castle and advance toward the attackers until they are within range of an enemy, and the attackers advance toward the defenders until they are within range of a defender.
Each unit can either move or attack once per round of combat. Once a unit is within range of a foe, they stop and then attack the next round. Only enough units necessary to defeat the opposing force stop to attack.
Each unit can either move or attack once per round of combat. Once a unit is within range of a foe, they stop and then attack the next round. Only enough units necessary to defeat the opposing force stop to attack.