Accuracy

From The Five Pillars

Closely related to Dodge, accuracy influences how hard the attacks of your units will hit units of your opponent.

For example (taken from my mage in freshman server: Mettuhs Mentor Mage [#127]'s Army:

Number.... Unitname............ Strength... Counter... Accuracy... Dodge... Hitpoints
A few....... Mountain Rises... 11959....... 800......... 42............. 50......... 3381
A few....... Mountain Rises... 10000....... 800......... 40............. 50......... 3400

First line are my Mountain Rises which are influenced by battle enchantments and spells, morale and so on.
Second line are the Mountain Rises which I got as reinforcements from a guildmember. These are never influenced by spells, morale, enchantments etc.
As you notice I boosted my units so their strength (=Attackpower) is higher, accuracy is a little better, but their hitpoints are a bit lower. What will be the overall effect?

Accuracy is the percentage of attackpower (AP) that actually reaches the enemy unit (if that unit wouldn't dodge at ALL).
Dodge is the percentage of attackpower that a units can avoid (Mountain Rises automatically avoid 50% of damage dealt to them).
Hitpoints (HP) is the amount of damage a unit can receive before it actually is killed.
Resistance is the percentage of damage that is negated.

Following equations will show the actual damage and killed units:
Potential dealt damage: # of units * AP * (accuracy/100)
Potential received damage: potential dealt damage * ([1-dodge]/100)
Actual damage: potential received damage * ([1-dodge]/100) * ([1 – resistance]/100)
Killed units: actual damage / HP

final equation
(# of killed units) = (# of units) * (AP) * (acc/100) * ([1-dodge]/100) *([1-res]/100) / HP

Other effects to consider:
Healing, Steal Life

Numerous spells, enchantments, items and some Hero Abilities influence accuracy, but a special effect that should be mentioned is Fatigue. Fatigue will lower the accuracy of a unit if it is hit before it can hit itself (max effect -6 accuracy if a unit is hit by three other units before it can attack itself; IF I'm correctly informed).

Thanks to Stark_ for the equations and to Pendarth for pushing to write this.