First World War Campaigns - More insight into combat odds

[ComradeP]

The terrain reduces incoming fire, it doesn't have an effect on assault odds. At least no effect that shows up in the game, odds are the same when attacking a unit in -5% or -20% terrain.

Bunkers, forts and pillboxes multiply defensive and offensive firepower directly and those have an impact.

You can see the difference: when moving a unit into regular terrain, the defense value in the unit information screen isn't modified. When you move the units into fortifications, it is modified. It is also modified by the frozen penalty (if any applies), for example.