Bunkers vs Trenches...

[LordDeadwood]

Bunkers do offer more protection than a trench. The +10 you refer to is an addition to the defense value of the unit occupying the bunker. So if a normal infantry battalion with a defense of 16 occupies a bunker, its defense value is now 26. Then the -20% is applied to the fire value of the attacking unit(s), in addition to whatever terrain value is present. On top of all this, bunkers are hard targets, whereas units occupying trenches retain whatever type of target they are. Lastly, vehicles do not benefit from bunker protection but do benefit from trenches and improved positions.