A free mod for Mount & Blade II: Bannerlord, by unstableai.
Realistic Shield Usage is a mod that allows you to play the game in a different way. In this mod, the game's units have their shields in front of them in all formations, except for two-handed weapons. This mod also changes the units' defensive abilities and attack speed.
The main units in the game now fight as if they're trying to live through the battle, not just to win it.
The shields have a realistic hitbox. This means that the units can be hit by arrow shots and other types of attacks.
The AI will become more intelligent and can make more strategic decisions. This mod also allows you to play with different formations and different strategies.
