There are many factors that determine how much damage your troops actually do in a battle.
Troop numbers in your army (per stack) and their Attack Power according to the Encyclopedia is the starting point...
Many other effects reduce that amount to the actual amount subtracted from Health points and determining the number of casualties.
This category has the following 8 subcategories, out of 8 total.
Pages in category "Battle Factors"
The following 16 pages are in this category, out of 16 total.