Battle bonuses can be divided into two types. Invidual bonuses that only affect the unit with the bonus and group bonuses that affect all units in the same army. Several bonuses exist in invidual form and group form.Here is a list of all bonuses and a description for them.
The most common bonus is the terrain bonus. It applies to unit when it's fighting in a certain terrain. If a unit has battle 20 and Open +10 for example that means that it will fight with battle 30 in open terrain.Terrain bonuses are common among 1 turn and 2 turn units.A road through a terrain is regarded as the terrain around it. A morale bonus can be based on a certain terrain but its still regarded as a morale bonus and not a terrain bonus. For example a unit may grant all units in the army +10 morale on open terrain. If there is a unit in that army with +10 open terrain it will get both +10 terrain and then +10 morale resulting in +20.
This bonus apply when the unit is in either defend position or attack position in the battle.
The anti air bonus kick in when the enemy unit is a flying unit. If the unit on the other side is a land unit but the next one is a flying unit the anti air bonuswont be active until the land based unit is killed. There is no way to target the flying unit before killing the units standing in front of it.
The ambush bonus is a chance to kill the enemy unit before entering battle. Ambush is a percentage chance and it only happen the first time a unit enters battle.Group ambush is a cumulative bonus which mean that group ambush from all units in the same army are added. Its possible to have 100% chance to kill the enemy unit with group and personalambush combined.Ward
Ward is a bonuses that negates ambush. If a unit has 50% ambush and the enemy unit has 25% ward the result ambush will be 50*0.25 = 12.5 (13) ambush. Ward is just like ambush cumulative.
Aura bonuses (Morale / Fear)
Morale and fear bonuses are aura bonuses that affect the entire army. The highest morale bonus in your army will be added to your units battle skill.Fear is the intimidating affect a unit have on the enemy. Fear removes battle skill from all units in the enemy army.Only the highest modifier apply for morale and fear. Having two units with +5 morale will result in +5 battle skill to all units.
Heroic bonuses (Leadership / Chaos)
Leadership and chaos are heroic bonuses similar to morale and fear. The difference is that leadership and chaos is found on hero units.The highest leadership bonus will be added to your units battle skill. The highest chaos removes battle skill from all units in the enemy army.Leadership and morale are cumulative with each other. You can have +5 morale and +5 leadership and the result is all units will have +10 battle skill.The same goes for fear and chaos.
Negating bonuses are bonuses that negates another bonus. Negate terrain +5 for example removes 5 from enemy terrain bonuses.Negate aura will remove from enemy morale or fear bonus.Negate heroism removes from enemy leadership or chaos.
Unaffected by city wall
This bonus make a unit unaffected by the city wall both when attacking and defending, which mean when it attack a unit in a city the defending unit won'treceive the bonus from the city wall.This also apply when defending, the unit with unaffected by city wall won't receive the defending bonus from the city wall when placed in a city or tower.
The swarm bonus makes units better in battle when several units of the same type fight together in the same army. If a unit have swarm 4(5) it will get +4 battle with each unit up to max 5 starting with the first unit.
Plunder is a bonus that apply when you take a city. When you capture a city the player owning the city loses the gold stored is the city (Gold / number of cities).The plunder skill decide how much of the gold is transferred to the warbaron capturing the city.The plunder value also dictates how much you get when you plunder a city.When you plunder a city you destroy all the production of the city and receive as much of the gold as it costs to buy the production multiplicatedwith the highest plunder percentage in the army. Most units have 40% plunder but some units are extra good or extra bad at plundering.