shields on ur back actually used to protect you from archers...In warband shooting the shield would cancel any attack, dont know why they didnt add it for Bannerlord aswell, it made archery alot more interesting, like shooting into melee, instead of shooting the enemy itself you could shoot his shield mid attack to stun him.
It made archers invincible from behind to ranged while shooting, not really an interesting choice to be had by the archer, that's just where it goes and provides them huge benefits. It still reduces damage.shields on ur back actually used to protect you from archers...
i dont understand why the shields work like this "physics" but doesnt protect when its on ur back