A combat bonus (also referred to as force multiplier)Erf-b1-p125 is a positive circumstantial influence that increases unit stats and makes it more efficient in combat.
Bonuses can derive fromErf-b1-p125:
Bonuses are very important in the combat system of Erfworld. In order to win a side should increase bonuses for their units while decreasing bonuses to enemy units.
Bonuses are probably multiplicativeErf-b1-p125 - bonuses of various types and even of the same type add upErf-b1-p113. There is also a stack bonus for stacked units that maxes out with 8 units.